Chapter VIII: Part 8

Facts are wanting with regard to these lesions in the domestic animals, but anatomical, physiological and pathological consideration are strongly suggestive of their occurrence. The vascular network of the spinal cord favors a tardy circulation, and this in turn is favorable to the arrest of solid bodies and the delay, proliferation and colonization of microbes. The median spinal artery receives a supply of blood by two trunks, right and left, entering by the intervertebral foramina at each intervertebral articulation. It has not, therefore, one continuous, equable, onward flow, but rather numerous independent currents corresponding to the entering vessels, and with intervening eddies or areas of comparative stagnation. The nervous material of the cord admits no large arteries but only capillary trunks which anastomose freely in its substance. This would seem to entail a sluggish flow, which would favor microbian arrest and colonization, even if the small size of the vessels serves to shut out clots of any material size. Finally the abundant venous plexus, and especially the two lateral venous sinuses, communicating freely with each other and, through each intervertebral foramen, with the extra spinal veins determine a similar tardy flow that should be favorable to morbid processes. If we pass back of these vessels, we find the posterior aorta to be at once the largest and the most direct channel for the entrance of emboli coming from the left heart or lungs. This danger is counteracted in greater part by the fact that the greater part of this blood passes into the large vessels which supply the liver, spleen, kidneys, stomach, bowels, and hind limbs, and while embolism is well known in these parts it has not been demonstrated as yet in the spinal cord. The toxins produced in infectious diseases and circulated in the blood can often lead to destruction of the endothelium, and inflammation of the deeper structures. In this way any circulating microbes find a ready infection atrium. Hektoen seems to have demonstrated this in the case of tubercular meningitis. By pressure of the neoplasm on the vessel or by fibroid thickening and contraction of the walls of the vessel, the subsidiary cord is denied its full supply, and degeneration of the nervous substance is invited. In the human subject degeneration of the cord has been shown to follow the line of such diseased arteries. Thrombosis follows in every case in which the serous coat is involved, and embolism can easily occur from clots small enough to enter the capillary vessels. Lamy’s experiment of blocking the small arteries with inert powder, shows that this will give rise to foci of hemorrhagic softening, which commence in the gray substance. The blocking, however, must be multiple to produce any material effect, as the free anastomosis of the spinal capillaries otherwise secures an abundant blood supply to adjacent parts. In case of an infective embolism the disease will advance even if the obstruction is single.

The general symptoms of these conditions would depend on the exact seat of the lesion, and treatment would have to proceed on general principles, the object being to check the inflammatory conditions, and trust to the _vis medecatrix naturæ_ in connection with rest and good hygienic conditions.

HEMORRHAGES INTO THE SPINAL MEMBRANES.
MENINGEAL SPINAL APOPLEXY. HÆMATORRACHIS. HEMORRHAGE INTO THE SPINAL
CORD. SPINAL APOPLEXY. HÆMATOMYELIA.

Definition. Causes: violent exertion, blows, falls, morbid blood,
fractures, caries, tumors, tubercle, aneurisms. Lesions: Clot between
or outside membranes in meningeal hæmorrhage, in gray matter and even
in white in myelon bleeding. Cord bulges. If survives, nervous matter
absorbed. Symptoms: Sudden stiffness or palsy of given areas; spasms
more common in meningeal extravasation. Rapid muscular wasting. No
fever at first. Treatment: cold to part; slings; atropia, ergot, lead
acetate. Later as for myelitis. Large clot may warrant surgical
interference.

In the first of these forms the bleeding takes place between the arachnoid and the two contiguous membranes—pia and dura, or outside the dura. In the second it takes place into the substance of the cord though it may encroach on the pia mater. Both conditions have been attributed to violent muscular efforts or contractions as in draught, racing, fighting, leaping, tetanic convulsions, also to blows on the back, or falls from a height. Morbid states of the blood in which there is a hemorrhagic tendency (scurvy, purpura, hæmophilia, anthrax) may be contributory causes. Spinal fractures, aneurisms, caries, tumors, and tubercle may be additional causes.

_Lesions._ In meningeal bleeding the clot is found outside the dura, or between the dura and arachnoid which may or may not be ruptured. A clot on the pia mater may press seriously on the cord or may cause rupture of the arachnoid. In hemorrhage of the cord, the effusion usually begins in the gray matter, though it may extend far into the white. It may be circumscribed to half an inch in diameter or affect almost the entire length of the cord. The cord may be distinctly enlarged at the point of effusion, and in exceptional cases the blood may have broken through to the membranes. If the patient survives, absorption and degenerations of the cord are inevitable.

_Symptoms._ In both forms there is a sudden attack, with stiffness or paralysis of given muscles and without hyperthermia. Rigidity and spasms of the muscles are more characteristic of meningeal hemorrhage, and early paralysis of the spinal. An early hyperæsthesia is also most significant of an effusion in the cord. Rapid muscular atrophy is also characteristic of this. The two conditions resemble meningitis and myelitis but come on much more suddenly and are unattended by fever.

_Treatment._ Such cases are not hopeful. Cold to the affected part of the spine, keeping the patient in slings to solicit the good effect of gravitation, and giving ergot or lead acetate internally are among the first indications. Later, the treatment would be practically the same as for meningitis or myelitis. In case of complete paralysis from the sudden formation of a large clot, it has even been advised to cut down on the seat of the injury and evacuate the blood, using antiseptic precautions.

SPINA BIFIDA.

This is an elastic swelling consisting of the spinal meninges enclosing a liquid, and in some cases the spinal cord as well, and protruding between the unclosed laminæ of the vertebral rings, usually in the region of the sacrum or loins. It is essentially an arrest of development on the part of the vertebræ and enveloping muscles and skin, and an extension of the cord and effusion of the meningeal and central spinal liquids, in the absence of their bony and muscular support. Hydrocephalus is no uncommon complication.

The _diagnosis_ may be based on the presence of an elastic, somewhat transparent tumor, projecting from the vertebral spines, at birth. If it contains a segment of the cord it is usually flattened, depressed on the summit and often associated with paralysis.

As occurring in the lower animals this need not be treated. In man, careful antisepsis and evacuation followed by injection of a solution of iodine 10 grs., iodide of potassium 30 grs., and glycerine 1 oz., have, in favorable cases, secured obliteration of the sac, but even then the recovery has rarely been complete and permanent. Paralysis and death have usually supervened.

SPINAL CARIES. TUBERCULAR OR OTHER INFECTIVE DISEASE OF THE VERTEBRÆ.

Spinal caries in old horses, sprains, fractures, infections; caries
often confined to articulating processes: anatomical form:
Axoido-atloid caries from poll evil, concussions, fights, rachitis.
Tubercle of bone and intervertebral cartilage in cattle. Symptoms:
distortion, stiffness, rigidity; stands day and night, sensory and
motor paralysis: localization of lesion; dyspnœa; spastic palsy back
of lesion; effect on tail, sphincters. Diagnosis: progressive
tenderness and stiffness of spine, distortion, localized exaltation or
depression of nervous function, osteoporosis, rachitis, caries,
tubercle, melanoma, abscess, infectious disease. Treatment: Sling in
narrow stall, good food, pure air, sunshine, tonics, phosphates.

As seen in the human subject spinal caries is usually tubercular and is known as “_Pott’s disease_.” As seen in old horses it appears to be rather a result of other infections, especially purulent, and may have started in connection with traumatic or mechanical injuries to the bones and ligaments. In such cases I have seen it repeatedly in hollow backed horses in which the line of the spine descended abruptly and extremely from the withers and rose again to the sacrum. The distortion was so great that the back appeared as if it could barely sustain the weight of the animal and yet the patients were kept at work and proved useful for light driving. Post mortem examination showed extensive caries and suppuration of the vertebral bodies, confined, however, to one or two segments as if due to a mechanical lesion. In the region of the loins it is much more likely to affect the articulations of the vertebral rings, because of the manner in which these are wedged into each other when the spine is pressed downward. In the neck where the normal movement is so much freer such injuries are much less common. Caries affecting the articular surfaces of the axoido—atloid joint is by no means uncommon. It may follow poll evil, or injuries sustained when a horse runs against a wall, or in the fights of bulls or rams. Disease of the vertebræ may be of the nature of rachitis occurring in this case in early life.

In cattle the disease is liable to be tubercular in which case, not only is the bone invaded but the morbid process extends to the intervertebral cartilage and projecting, presses on the spinal meninges and cord. It may even encircle the entire spinal cavity and strangle the cord. If the pus should extend downward it may form abscess under the spine, and rupture into an internal cavity or externally.

_Symptoms._ Injuries and disease of the vertebræ may last for a length of time without implicating the spinal cord or nerves. They may then cause only distortion, with stiffness or rigidity of the spinal column. When, however, the displacement of the injured, carious or tubercular bones, the distension of the abscess or the increase of the hyperplasia leads to pressure on the nerve roots, the meninges or cord, nervous symptoms are likely to be developed. Compression of the nerve roots—sensory or motor—may cause sensory or motor paralysis or both, limited to particular areas the outline of which will point to the precise seat of the lesion. If in the recti of the head and other muscles of the neck, it points to the anterior cervical vertebræ. If in the fore limbs, it points to the posterior bones of the neck. The implication of the diaphragm would incriminate the fourth and fifth cervical vertebræ. If in the crural muscles or those of the quarter and thigh, the lumbar vertebræ must be looked to. The implication of the nerves of the back, while impairing the functions of the intercostal and abdominal muscles, produce less marked symptoms than when the limbs are involved.

When the disease extends deeper so as to implicate the meninges and especially the cord, there is evidence of impairment or interruption of conduction in the cord in addition to the simple involving of the nerves that emerge at that point. Thus serious disease or pressure on the cervical part of the cord in front of the fourth vertebra will make respiration difficult or impossible and speedy asphyxia may ensue. The paralysis of all parts behind the lesion is overlooked, in view of the fatal nature of the paralysis of the intercostals and diaphragm. If the interruption of conduction is incomplete there may be spastic paralysis and hyperæsthesia in the limbs and trunk back of the lesion.

If the dorsal cord is involved so as to render conduction imperfect there will be at first imperfect control of parts posterior to the lesion, and when still further implicated, flaccid or spastic paralysis, especially of the hind limbs and tail. When it implicates the lumbar region in addition to the paralysis named for the dorsal, there will be incontinence of urine and even relaxation of the anal sphincter. In a case of acute tuberculosis in a cow, supervening on an ancient tuberculous lesion, as seen by the author, there were imperfect control of the hind limbs and uncertain gait, with tenderness of the dorsal region as if the animal had sprain of the back.

_Diagnosis_ of these cases of vertebral disease may not always be possible in the early stages, yet the symptoms of progressive tenderness and stiffness in the region of the spine, the distortion in some instances of the spinal column, the subsequent appearance of localized motor and sensory symptoms, and later still the spasms or spastic paralysis in all parts behind the seat of the lesion, will be strongly suggestive of such a disease. When indications exist of osteoporosis, rachitis, or tuberculosis, of caries, abscess, or infectious lesions of the cervical or dorsal spinal region, the inference is still stronger. Then if reaction occurs under the tuberculin test, or if the urine contains an excess of phosphates in the herbivora, the case may be diagnosed with certainty.

_Treatment._ This will rarely be admissible on account of the expense and uncertainty of result. Some meat animals may be killed for food. If otherwise, keep in narrow stall where the animal cannot turn even the head, feed from moderate level to avoid movement of the spine by the upward and downward movements of the head. Gentle brushing is useful as a means of cleanliness, and of toning up the muscular system. Nourishing food of an easily digestible kind is essential, and pure air and sunshine are important auxiliaries. A course of cod liver oil with bitters may be given to improve the general health, calcium sulphide may be tried in case of suppurative caries, and calcium phosphate will usually be desirable to improve the nutrition and consistency of the osseus system. In case of a valued patient which it is desirable to preserve for reasons of sentiment or affection, or for breeding purposes, one might be warranted in continuing a long and expensive course of treatment, but in the regular run of cases considerations of humanity and economy would counsel the prompt destruction of the animal.

SLOW COMPRESSION OF SPINAL CORD. PARALYSIS.

Causes: Caries, vertebral diseases and lesions, neoplasms,
actinomycosis, tubercle, abscess, organizing exudates, parasites.
Melanoma, cholesteatoma, sarcoma, papilloma, lipoma, glioma,
chrondroma. Symptoms: advance insensibly, or by sudden leap with
exudate, spasm, paresis, transverse, senses clear, muscular atrophy,
advance from behind forward. Cervical, dorsal, lumbar lesions.
Bladder, sphincters, tail. Symptoms increased by movement. Treatment:
according to lesion. Tumors, hopeless. Blood clots, Actinomycosis.
Analgesics. Electricity.

_Causes._ Slowly progressive compression of the cord has been already noted as resulting from caries and other diseases of the vertebræ. It remains to notice such as result from the growth of tumors and other neoplasms in the spinal canal. In the horse these are commonly melanoma (in white horses), sarcoma, encephaloid, papilloma, cholesteatoma, and osteoma; in cattle, beside tubercle and actinomycosis, have been found sarcoma, lipoma, osteoma and glioma; and in dogs sarcoma and chondro-sarcoma. Chronic abscesses may be met with in all animals determining the same class of symptoms by slow pressure. In the same manner exudates in process of organization contract, and are liable to compress the myelon. Cadeac draws attention to a calcic degeneration of exudates in the dura mater of the dog (ossifying pachymeningitis), and of ossification of the intervertebræ cartilages with vegetations on their surfaces. Parasites also exercise a growing pressure, especially echinococcus, in cattle cysticercus mediocanellata, in sheep and dogs cœnurus, and in pigs and dogs cysticercus cellulosa.

=Melanoma.= In gray and white horses, with disseminated melanosis, the spinal canal is often involved, the pigmentary sarcoma appearing in small formations and sometimes large enough to determine injurious pressure. In the early stages these may cause stiffness and lameness referable to particular muscles or groups, varying in situation, even as to the limbs affected, at successive dates, and finally merging into paraplegia.

=Cholesteatoma= is less common than in the encephalon, yet one is reported by Dexler as attached to the pia mater and possessed of great firmness, crisply crackling under the knife. It doubtless secures accretions under meningeal exudates like those of the choroid plexus.

=Sarcoma= and =encephaloid= are usually found in connection with the dura mater, and of small size, but numerous. They often surround the roots of the spinal nerves, and here as on the cord exert sufficient pressure to impair nervous function.

=Papilloma= has been found connected with the pia mater and of marked vascularity. The author has found one in the ewe in a case of the neurasthenia of advanced gestation.

=Lipoma= is also rare. Osseous growths are common, being favored by sprains and injuries. All show a marked predilection for the lumbar and last dorsal vertebræ. This may be partly explained by the liability to injury and to disease invasion through the interlocking of the joint surfaces of the rings. _Osteophytes_ growing from the intervertebral cartilage are common in the dorsal region as well.

=Glioma= has been found in cattle, occupying the substance of the cord itself and growing to the size of a hen’s egg or even of the closed fist. The cord is gradually atrophied and paraplegia is inevitable.

=Chrondro-sarcoma= has been found growing from the intervertebral fibro cartilage of dogs.

The _Symptoms_ may be deferred for a length of time on account of the accommodation of the myelon to the slowly increasing pressure. When they do become manifest, it is usually at first by insensible gradations so that for a time their existence is questionable. Yet a case will sometimes reach a sudden climax, by reason of a blood extravasation or inflammatory exudate, and the signs of sudden pressure or acute myelitis or meningitis supervene. In the absence of sudden access of trouble, the symptoms are those of a slow increase of _motor troubles_ (local paresis, paralysis, paraplegia), or _sensory_ (hyperæsthesia, anæsthesia). Spasms may occur early or even later in the disease. From disorders due to cerebral lesions the morbid phenomena are distinguished by being paraplegic rather than hemiplegic; sensori-motor rather than sensory or motor; local rather than general; with intelligence and special senses clear, rather than dull or abolished; associated with marked muscular atrophy in the affected parts; advancing from behind forward rather than uniform throughout the body.

The area of nervous disorder points more or less clearly to the seat of the lesion. Early implication of the fore limbs, and then later of the hind, suggests lesion of the cervical region. Dyspnœa tumultuous heart action, or vertigo may coincide. Tardy movements of the hind limbs, imperfect balancing, dragging, swaying, knuckling, involuntary flexions of stifle or hock, flexor contractions, standing on toe, cramps, paraplegia, indicate lesion in the dorsal or lumbar region. There may be palsy of the rectum, anus, bladder, sphincter vesicæ, penis, and vulva. Paralysis or other nervous disorder of the tail and sphincters ani and vesicæ, without implication of the hind limbs or quarters, may bespeak lesion in the terminal end of the spinal cord.

With paralysis of the bladder the penis may be pendent out of the sheath, or being retained within it, the urine may dribble constantly into and from that cavity, and the vulva may be soft and flaccid. When the anus is involved, the adjacent part of the rectum usually participates becoming overloaded, the sphincter is soft and lax and allows a constant oozing, and the exposure of the mucosa. The paralytic tail hangs between the thighs, limp and flaccid, and becomes saturated with manure and in females with urine.

Even in the earlier stages the symptoms are usually greatly aggravated by compulsory movements like turning in a circle, walking up hill, or (in dogs) up a stair, the arched back, the pendent head, and hesitating planting of the foot suggests walking on pins. For a more exact localization of the lesion the reader may consult the table indicating the functions of the different parts of the spinal cord. The early fatigue under exercise grows as in other progressive spinal lesions.

_Treatment._ In most cases this is hopeless. Tumors, bony and calcic growths, tubercles, degenerations and absorption of nervous tissue are practically beyond remedy. A blood extravasation may be largely absorbed, leaving only the permanent changes in the nervous tissue. In this time is the main element. Actinomycosis may sometimes be successfully met by a course of potassium iodide, when, if the nervous lesions are slight, a fair recovery may be secured. In the majority of cases, however, the practitioner is limited to measures for palliation of suffering by atropia, chloral, phenacetin, etc., or by nerve stimulants like nux in small doses, or by weak currents of electricity. In meat producing animals, it is often the best course to fatten rapidly, or to turn over at once to the butcher.

DILATATION OF THE CENTRAL CANAL OF THE SPINAL CORD. SYRINGOMYELIA.

This means literally a cavity in the spinal cord but is applied to cavities formed by dilatation of the central spinal canal, or by an excavation in the nervous tissue immediately adjacent and usually communicating with a dilated segment of the canal. In man it is usually the result of an active proliferation of the epithelial cells of the canal, blocking the same, or extending into the adjacent nervous tissue in the form of a glioma. In different cases in dogs it occurred as the result of pressure. It has been seen in dogs, cats and Guinea pigs, as a casual lesion and as the result of experiment.

In a case reported by Lienaux it extended for practically the whole length of the cord, varying in form and size at different points. In the lumbar portion it was only slightly dilated, in the dorsal it was very irregular with prolongations into the gray matter, toward the cervical enlargement, its transverse section resembled an inverted V, and in the anterior cervical part it was unevenly rounded. Notable changes were cell proliferation and subsequent degeneration with the formation of cavities, thickening of the neuroglia, and compression and even obliteration of the vessels with circumscribed areas of necrosis, terminating also in cavity formation.

_Symptoms._ These vary with the nervous structures invaded, atrophied or destroyed. Invasion of the anterior horns of gray matter, causes trembling and muscular wasting. The implication of the superior horns determines more or less marked anæsthesia. Hyperæsthesia, spasms, paresis and paraplegia are also seen but no symptom nor group of symptoms is diagnostic of the exact lesion.

_Treatment_ is manifestly hopeless.

NEURASTHENIA IN PREGNANT EWES.

Causes: inactivity, lowered muscular and nervous tone, twin pregnancy,
approach of parturition, dry (clover hay) ration, concurrent diseases.
Symptoms: moping, anorexia, depression, stupor, blindness, paresis,
lethargy. Prevention: open air life, exercise, high muscular
condition, avoidance of debilitating and relaxing conditions.
Treatment: hygienic, nerve tonics, attend to concurrent diseases.

Neurasthenia has been defined as an incompetency of the nervous system, leading to early fatigue, and inability to recuperate from the prostrate condition. Pending a better knowledge of the affection, I have given this name to an asthenic affection seen in pregnant ewes when nearing the completion of the period of gestation.

_Causes._ In a large number of cases I have found several conditions so constant, not to say invariable, that they seem to deserve special attention in the list of causes:

1st. =Enforced inactivity.= In every instance that has come under my notice the ewes have been confined for several months to a barn or at most a confined yard so that exercise became impossible. The muscular system was flabby and soft, although as a rule there was abundance of fat, and the number of red globules did not vary much from the normal. In an animal that is naturally so active, and so accustomed to outdoor life the reduction of tone and vigor is to be expected. The same evil shows in other directions, thus after a snowy winter and close confinement the crop of lambs will sometimes perish of goitre without exception, while in subsequent years, with enforced exercise of the ewes, practically all escape.

2d. =Twin lambs= have been found in the womb of almost every case examined. The extra drain upon the system, and the depressing action of the load on an atonic ewe together with the symptomatic irritation are to be noted.

3d. The near approach of the =completion of gestation=, the cumulative effect of a long pregnancy, and perhaps the absorption of metabolic products from the fœtal membranes in course of preparation for detachment, and of leucomaines from the physiologically active or developing mammæ, doubtless have a prostrating influence on the susceptible nervous system.

4th. All had been fed on =clover hay= either as an exclusive diet or as part of their ration. This is sufficiently nutritive, as testified by the fat condition of the patients, but it may be that it was too nitrogenous for such an inactive life. Again the clover hay usually abounds in cryptogams and bacteria and their products, which may have contributed somewhat to the asthenia.

5th. =Concurrent diseases=, in individual cases or flocks, manifestly contributed to the general loss of nervous power. In some the bowels were studded with the nodules of the œsophagostoma, in others œstrus larvæ had extensively invaded the nasal sinuses, one had congestion of the mucosa of the small intestines, some had congestion and fatty degeneration of the liver, others had fatty kidneys, and one had a papilloma pressing on the spinal cord. Manifestly diseases and degenerations of various kinds would still further undermine nervous energy and add to the atony.

Cold and heat did not seem to dominate, as most were kept in warm barns, and wore heavy winter fleeces, while one clipped early in December, and kept in an atmosphere of 40° to 55°, was attacked in the second week of January.

As this experience was had in a goitre district it may become a question whether the poison of this disease was a causative factor. Goitre was not a prominent feature in either ewes or lambs.

_Symptoms._ Variable. The most prominent are, leaving the flock, moping alone, grinding the teeth, drooping and trembling of head and ears, temperature normal or subnormal (100.5°), respiration 24, pulse 80, feeds and ruminates sparingly, bowels normal, buccal mucosa pale, conjunctiva hyperæmic, in some cases stupor and partial blindness, the animal walking against racks or fences, walk is slow and unsteady, the muscles feel soft and flabby, the abdomen may be full, but its walls are quite flaccid so that the lambs can be easily felt. As the disease advances all symptoms are aggravated, food is no longer taken, rumination ceases, the ewe remains recumbent, cannot be made to rise, and when lifted and carried makes no struggle. After 24 hours of this helpless condition death supervenes. In some instances labor pains have come on and the ewe has perished in a vain effort at delivery. Illness lasted about a week.

Prominent _lesions_ have been noted under causes. It need only be added that no notable difference from the normal was found in making a count of the red globules, and the size of the individual globule was normal or only perceptibly smaller as is to be expected in a dense plasma. In different cases there was found congestion of the abomasum, small intestine, liver and brain.

_Prevention._ The most important measure is to maintain a strong, well-developed muscular system, and a vigorous nervous tone by a sufficiency of out door exercise during the winter months. Half a mile or a mile at least should be given daily to the breeding ewes, no matter what the attendant difficulties. If clover hay is musty it should be replaced in whole or in part by another kind. Parasites and other diseases which tend to lower the general tone should be appropriately treated.

_Treatment._ When once established, the disease has not been successfully treated. Nerve tonics are indicated.

NEURITIS. PERINEURITIS.

Definition. Causes: traumas, poke, stanchions, collar, yoke,
interfering, neurectomy, fractures, tumors, callus, rheumatism, gout,
violent overdistension. Lesions: nerve sheath red, swollen, exudate,
leucocytes in excess, fibroid thickening, nerve atrophy, degeneration,
axis granular, myelin in oily globules, peripheral extension. Muscular
degeneration and atrophy. Symptoms: tenderness, swelling, muscular
atony, wasting, spasms, twitching, decreased excitability, paralysis,
in section swelling on proximal end. Prognosis: disability for weeks,
months or year; response to electric current, operability of tumors,
curability of rheumatism or gout, hopeful conditions; long standing
degeneration, etc., unpromising. Treatment: rest, soothe, anodynes,
splint with soft pad, essential oils, lead and opium lotion, ice,
snow; derivatives; laxatives; diuretics, anti-rheumatics,
Faradisation.

_Definition._ Inflammation of a nerve leading to paralysis of the parts to which it is distributed.

_Causes._ Traumatism is the most common factor. Among the common examples are injury of the seventh nerve above the angle of the lower jaw, by a poke worn in pasture by the horse, or by stanchions in the cow. Hogs may suffer from blows of the triangular neck gear worn to prevent them from breaking through fences. Blows by the yoke, incised and contused wounds implicating the nerve, such as neurectomy, and the blows received in interfering, and compression by tumors or bony growths, are familiar examples. Fractures with displacement, notably those of the sacrum and proximal end of the coccyx with caudal paralysis, are not uncommon. In fractures of the limbs the pressure upon or wounding of a nerve. Again, the callus on the seat of fracture may induce neuritis by pressure, as may also the projection of the end of a bone in luxation. Rheumatism affecting the nerve sheaths and, in birds and swine, gout, are additional factors. Violent overdistension, and even chronic muscular spasm, are quoted as causes.

_Lesions._ The early changes are mainly in the connective tissue sheath, which becomes hyperæmic, red and swollen, with a gelatinoid exudate and a great multiplication of leucocytes. Later, the interfibrillar connective tissue is involved and the nervous substance proper undergoes hyperæmia and degeneration. The axis cylinder undergoes granular degeneration and the myelin breaks up into oil-like globules. The lesions are at first limited in extent, though there may be more than one focus, and the resulting degeneration of the nervous filaments advances toward the periphery in accordance with Waller’s law by which disease changes proceed rapidly in parts cut off from their trophic cells.

The muscles supplied by the inflamed nerves also rapidly degenerate. The fibres shrink in size, and lose their striated appearance, becoming distinctly granular, and pale. Round cells are formed in excess in the sarcolemma and muscular fibre, and if the morbid condition persists there is fibroid degeneration, cirrhosis and contraction.

_Symptoms._ In the absence of the subjective element of pain, which is the most constant symptom in man, we must rely mainly on the exquisite tenderness on pressure along the line of the nerve, but localized at some particular point, on the swelling at such tender point and on the loss of muscular power or even of sensation in the tissues corresponding to its peripheral distribution. The muscles may be hypersensitive and are usually flaccid if not from actual paralysis, still from the pain which attends on their contraction. In some cases they are the seat of clonic spasms or twitching. Under a current of electricity they show a decreased irritability which bears a direct relation to the grade of degeneration which has occurred in the nerve fibres. In cases of deep-seated neuritis paralysis may be the only appreciable symptom. In traumatic injuries like bruises of the seventh nerve or fracture of the sacrum the local swelling and tenderness are marked initial symptoms, upon which supervene the paralysis and atrophy of the muscles cut off from full innervation. In neurectomy the tender swelling in the stump which is still in connection with the nerve centre may amount to a distinct neuroma, while the peripheral and detached portion of the nerve steadily loses its irritability as shown by electric stimulus.

_Prognosis._ This will depend on the nature of the lesion. A single transverse section of a nerve, without loss of substance may be repaired in a few months, while with loss or degeneration of a considerable part of its substance it may maintain a paralysis for years or even permanently. Lesions due to slight bruises may recover in a few weeks, while the more severe ones will persist for months or years. The response to electric stimulus distal of the lesion, is a guarantee of the absence of degeneration and a feature hopeful of recovery. Pressure by bony displacement or neoplasia must be done away with as the first condition of improvement in such cases. Rheumatic and gouty cases will persist until these constitutional infirmities are corrected.

If the neuritis and paralysis have lasted for any length of time, the degeneration of the muscles will keep up a degree of muscular weakness (and if in the limbs lameness) after the repair of the nerve has been completed.

_Treatment._ Rest is the first consideration accompanied by soothing and anodyne application to the inflamed nerve. When neuritis exists in a limb a softly padded splint may be useful at first. The skin over the inflamed nerve may be rubbed by one or a combination of the anodyne essential oils, (oil of cajeput, oil of peppermint, oil of lavender). If the pain and tenderness are extreme, a bag of ice or snow may give relief and should be kept applied for a length of time. Or hot fomentations with a lotion of lead and opium may be preferred especially in rheumatic cases. If blisters seem to be called for, aqua ammonia and oil of turpentine may be added to the essential oils, or muriatic acid may be applied with a glass rod in points along the line of nerve. A laxative of Epsom or Glauber salts will often prove of great value at the outset and may be followed by diuretic doses of potassium iodide, potassium nitrate or acetate, and in rheumatic cases sodium salicylate. In these last forms, as also in gout, the carbonates and acetates of the alkalies, colchicum, and salicylates are especially to be persisted with. In these, too, rubefacients and blisters are often of essential value and may be repeated again and again.

Faradism is of little account during the active stage of neuritis excepting as a test of the progress and extent of the degeneration, but when inflammation has subsided nothing contributes more to the restoration of the tone and healthy nutrition of both nerve and muscle. The current is to be sent along the line of the paretic nerve and muscles for ten or fifteen minutes at a time and not less than once a day.

NEURALGIA.

Intermittent or remittent pains, in line of nerve without
inflammation, or other structural lesion. Diagnosis: lameness,
stiffness of particular muscles having a common nerve. Unnatural
position habitual. Pain of inflammation and of neuralgia. No
functional change. Rheumatism. Tumors. Causes: lead, rheumatism, gout,
auto-poisons, cold, anæmia, reflex. Facial neuralgia,
occipito-cervical, dorso-intercostal, lumbo-abdominal, sciatic.
Treatment: elimination, of lead, etc.; intestinal antiseptics, tonics,
hot water, anodynes, arsenic.

This is characterized by pain paroxysmal, intermittent or remittent situated in the course of given nerves. It must be a pure neurosis and unaccompanied by any specific structural lesion like inflammation, degeneration, atrophy, hypertrophy, tumor or the like. It is therefore manifested subjectively and cannot be easily identified in the lower animals. Nevertheless, Lafosse, Zundel, Genée, and others have recorded cases, their conclusion being deduced from symptoms which were held to indicate nervous suffering in the absence of any structural lesion whatever. _A priori_ one can with difficulty escape the conviction that neuralgia must exist in the lower animals as in man, and the only drawback to its recognition is the difficulty of diagnosis.

The first step in such diagnosis must usually be the presence of lameness, stiffness or indisposition to free movement of some particular muscle or group of muscles deriving their innervation from a particular nerve. Or there may be a particular position habitually assumed such as semi-closed eyelids, drawn back ears, laterally inclined neck which strongly suggests nervous suffering. Next, there must be the exclusion of any appreciable structural cause and especially of inflammation. The three prominent features of the pain of inflammation is that it is aggravated by pressure, it is heightened by movement, and it is accompanied by some decided alteration of the function of the part. If there are at the same time exudation and swelling, inflammation is all the more certainly indicated. In a neuralgic pain on the contrary pressure does not increase the pain: it may even alleviate it: movement of the part may be rather satisfactory to the patient than painful; and the disturbance of function, contractile, secretory, trophic, is not perceptible. There is no local exudation nor swelling to account for the nervous disorder.

The liability to confound the affection with a neuritis more centrally situated, but the pain of which is referred to the periphery of the nerve, is to be obviated by a tracing of the nerve along its course to the nerve centre so as to identify any centre of tenderness, and also by the implication of all the peripheral branches coming off ectal of that point.

Again, rheumatism may be easily confounded with neuralgia, but here the affected nerve and muscle and even the skin over it is liable to be very tender to the touch or pinch, and if at all acute some hyperthermia is present. Like rheumatism, neuralgia shows a tendency to shift from place to place.

Pains due to pressure on the nerves by tumors, aneurisms, and other swellings, are constant, whereas neuralgic pains are marked by remissions and aggravations and even by intervals of complete relief.

_Causes._ The toxic neuralgias are illustrated by chronic lead poisoning, in which, in man, there are wandering pains like those of rheumatism, and in the lower animals muscular stiffness and contractions which suggest a similar condition. In man, too, gout is a common factor, and in pigs and birds in which this condition exists, stiffness and evidence of suffering may well be at times attributed to a similar cause. How many other forms of chronic metallic poisoning and poisoning by morbid autochthonous products of indigestion are attended by disorders of innervation and nutrition, it is as yet impossible to say. The direct action of cold, an anæmic condition of the nerves, and reflex action from distant sources of irritation are among the other invoked causes. Inflammation in the _nervi nervorum_ is also invoked as a factor, but in this case the symptoms would not accord with the rule given above, since the nerve trunks would be very tender to touch or pressure, and the suffering would be unshifting and shown permanently in the one seat.

=Facial Neuralgia.= Lafosse and Zundel describe as cases of this kind those in which periodically the horse’s eyes are fixed and shining, the ears drawn back and depressed as in vice, the head at intervals bent on the neck, with plaintive neighing, rubbing the head on the stall and pawing. Those cases of twitching of the head or rapid jerking of the ears in horses, when they have been driven for some distance, and which are relieved by wearing a close net over the nostril or by section of the trifacial nerve at the infra-orbital foramen, manifestly partake of this character.

=Cervico-Occipital Neuralgia.= Lafosse speaks of this as often mistaken for torticolis, the head being turned to the affected side during the paroxysms. In man this is often a result of cold draughts on the back of the head, and associated with tender points on the course of the nerve, between the mastoid and the median line.

=Dorso-intercostal neuralgia= causes pain in deep inspiration, and =lumbo-abdominal neuralgia= develops tenderness in the loins, in one testicle, or in one lip of the vulva according to Lafosse. Diagnosis between such cases and neuritis, spinal disease, and other obscure nervous affections must be very problematical.

=Sciatic Neuralgia.= This is described by Zundel as causing jerking and lameness in the affected limb, sometimes aggravated and sometimes improved by work and associated with muscular weakness or paresis. Sciatica in man is, however, rarely a simple neuralgia, but partakes rather of the nature of a neuritis, and there is no good reason for supposing that the disease of this nerve in the lower animals is other than an inflammatory condition.

Leclainche after consideration of the testimony adduced, is of the opinion that we still lack absolute evidence of uncomplicated neuralgia in the domestic animals.

_Treatment._ For =toxic= cases elimination of the poison is the first consideration. For _lead_ carefully graduated doses of iodide of potassium to carry off the offending agent without increasing its poisonous action must be continued as long as the metal is passed by the urine. It may be followed by a course of strychnia, by electricity, massage and blisters. Gouty subjects may be treated with salicylate of soda, alkalies, or colchicum. The victims of Bright’s disease must be treated for the kidney affection.

Where there has been =trouble of the digestive organs=, intestinal antiseptics (salol, sodium salicylate, bismuth-salicylate, beta-naphthol) and small doses of arsenious acid will sometimes benefit.

In =anæmic conditions= a course of tonics (cod liver oil, iron, quinine, nux vomica) are indicated, and, to improve the local blood supply, nitro-glycerine. A rich stimulating ration, currying, an open air life, and sunshine (in summer a run at grass) are called for.

In man with a suspicion of =traumatic origin=, W. H. Thomson strongly advocates a persevering use of the hot water douche to the parts first affected, the hypodermic use of morphia and atropia, and in case of local anæmia nitro-glycerine every three hours. Where there is a suspicion of inflammation he successfully employs absolute rest, with opium narcotism so as to abolish the pain, for twenty days if necessary. Aconite, antipyrin, acetanilid, phenacetin, exaglin, and gelsemium have their advocates, and may benefit in individual cases. A course of arsenic is often successful, and phosphorus and ergot have each proved of value.

ATROPHY OF NERVES.

From arrest of function, from lesions, pressure, distal, but at times
central of lesion. Symptoms: Loss of function advancing to paralysis.
Muscle atrophy. Prognosis: in absence of incurable cause, is hopeful.
Union of divided ends, restoration of function. Treatment: time,
ligature of divided ends.

This is usually the result of arrest of function. It may be due to transverse section of the nerve, as in surgical neurectomy when the separated peripheral end of the nerve gradually wastes. It may come from contused wounds implicating the nerve and causing destruction of its substance. It may be from tumors or other neoplasms pressing on the trunk of the nerve and preventing the passage of nerve currents. Or, inflammatory effusion may press on the nerve, as happens often to the crural in hæmoglobinuria. Or the pressure may come from enlarged mediastinal glands, or even from the distended posterior aorta under habitual violent exertion so as to permanently incapacitate and atrophy the left recurrent laryngeal nerve as in chronic laryngeal paralysis (roaring). Similar wasting occurs in other nerves under corresponding conditions. Atrophy may, however, extend centrally from the peripheral end of a nerve when it can no longer remain functionally active. We find an example of this in the atrophy of the optic nerve up to the commissure when the eyeball has been excised. A similar condition is often seen in horses in which the integrity of the eye has been completely destroyed in connection with recurring ophthalmia.

The _symptoms_ attendant on atrophy of a nerve are those of impaired function gradually advancing to complete paralysis of motion or sensation. In cases of a complete breach of continuity as in section or severe traumatism the entire loss of function necessarily precedes the atrophy. Again, when it comes from destructive changes in the coats and media of the eye, and of the ganglionic cells of the retina, the atrophy of the nerve trunk proceeds simultaneously with the lesions of the organ of vision.

The _diagnosis_ will in many cases be easy as deduced from the traumatic or surgical lesion. In other cases it may be made with certainty from the complete muscular paralysis, wasting and degeneration of the muscles supplied by the nerve, and by the history of the case (hæmoglobinuria in atrophy of the triceps extensor cruris, roaring in atrophy of the laryngeal muscles and recurrent nerve). In other cases, as in the eye, we have the atrophy of the eyeball, the distortion or complete paralysis of the iris, the opacity of the lens, or the exudation into the vitreous, choroid and retina when these can still be observed.

_Prognosis_ will depend on the cause. With a nerve severed with a knife or crushed in a part of its course and atrophied, without destructive changes in the organs in which it is distributed, repair is possible and to be expected in time.

_Treatment_ is expectant, yet inflammation must be subdued, tumors removed, divided ends ligatured, etc.

DISEASES OF THE URINARY ORGANS.

Relative prevalence in man and animals. Causes of difference. Kidneys
as eliminating organs for nitrogenous material, toxins, bacteria,
mineral, vegetable and animal poisons, diuretic drinking water,
condition powders, cantharides, urea, etc. Suppression of urine,
precipitation of urine. Filtration through kidney. Secretion. Urinary
solids. Nervous control of secretion. Excess.

Diseases of the urinary organs are less prevalent in the lower animals than in man, owing largely no doubt to the greater simplicity of their habits of life and to the comparative shortness of the lives of those that are kept for meat producing. It is a mistake, however, to suppose that they are so infrequent as would appear, since the absence of subjective symptoms in the animal allows a number of the milder forms of renal disease to be passed over without recognition.

In man the excessive consumption of animal food, the lack of exercise, the abuse of alcohol, the prevalence of venereal diseases, conduce largely to renal troubles, while animals in general escape. Yet animals suffer much more extensively than is generally supposed. The kidneys are, as in man, the eliminating organs for superfluous and waste nitrogenous matter, and in overfed animals may be overcharged with this work. They are the general emunctories for the soluble poisonous products of bacteria and plants, which may stimulate the urinary secretion, and from these irritation may result. It is through the kidneys that the bacteria themselves largely leave the animal body, and trouble is liable to come during their passage. Further, exposure to cold tends to =increase the urinary secretion=, over-stimulating the kidneys, and the same may come from diuretic drinking waters and condition powders, also from cantharides and other diuretic agents applied to the skin. Urea and many toxins are diuretic, hence the occurrence of polyuria at and after the crisis of fevers.

On the other hand =suppression of the urinary secretion= may occur in connection with profuse perspirations in hot weather, with prolonged diarrhœa, or with privation of water, and in such cases the liquid becomes concentrated and irritating and there is a disposition to precipitate its solids under slight disturbing causes. As conducive to such precipitation may be named foreign solid bodies, bacterial ferments and probably the goitre poison since gravel and calculus are common in goitrous regions.

There are two forms of elimination through the kidneys. 1, _filtration_; 2, _secretion_.

1. _Filtration_ is referred to the glomeruli, and is determined by the relative blood pressure. Increase of pressure causes increase of watery transudation. Digitalis increases heart action and arterial pressure, and accidently urination. Excessive consumption of water and watery liquids increases intravascular tension, and the amount of urine.

2. _Secretion_ is referred to the columnar epithelium of the convoluted tubes. It is by the elective affinity or selective power of this epithelium that the solids of the urine are abstracted from the blood and passed into the urine. Crystals of uric acid have been found in these cells and it is supposed that the abundance of water furnished by the glomeruli, irrigating these convoluted tubes, dissolves and washes on the various solids and other products with which the epithelial cells are charged. The protoplasm of the cells becomes saturated with the urea, uric acid, hippuric acid coloring matter (indican, urochrome, etc.), and this is washed out, passing by exosmosis to the liquid of lesser density with which the tubes are filled.

Nervous Control of Urinary Secretion.

An electric current through the renal plexus of the sympathetic (vaso-motor) lessens, or suppresses urinary secretion (inhibition).

Cutting the nerves of this plexus causes excessive vaso-dilation, renal pulsations synchronous with heart beats and arterial pulse, and great increase of urine. A similar increase comes from the application of cold to the surface, from fatigue, from heat exhaustion, from irritation of the floor of the fourth ventricle just in front of the origin of the vagus and from section of the splanchnic nerve. This last is, however, much less marked and more transient than from section of the renal nerve noted above; the latter causing dilation of the renal vessels only, and increased pressure, whereas the former causes dilation of the abdominal organs generally, diverting the blood largely to other parts than the kidney and preventing the same increase of pressure in the vessels of the latter. For the same reason transverse section of the medulla oblongata, or of the spinal cord as far back as the seventh cervical vertebra, lessens or interrupts the urinary secretion, the pressure in the kidney being reduced by the diversion of much of the blood elsewhere. This influence of the nervous system on the urinary secretion seems to be mainly or entirely one of increase or decrease of blood pressure in the kidney. For this reason a weak heart tends to lessen urinary secretion.

=Excessive increase= of urine is only important when continuous and in the absence of visible cause, such as diuretics.

PHYSICAL PROPERTIES OF THE URINE.

Color, yellow, red, brown; horse, ox, calf, sheep, goat, dog, cat,
bird. In disease: pale yellow, with water in excess; deep yellow, red,
brown with solids in excess, urobiline, biliverdin, hæmoglobin.
Extraneous colors. Bilharzia. Translucency: Turbidity: horse,
ruminants, carnivora, pig. In disease, horse, other animals.
Consistency, viscous, stringy, tarry; odor, horse, dog, cat,
ammoniacal, fœtid, drug odor. Specific gravity, estimate of solids;
reaction, acid, alkaline, neutral; morbid chemical changes, sodium
chloride, phosphate, alkaline, earthy, indican, urea, uric acid,
hippuric acid, phenol, creatinin, acetone, oxalic acid, allantoin,
xanthin, hypoxanthin, cyanuric acid, leucin, albumen, glucose, bile
salts and pigments, blood, hæmoglobin, epithelium, pus, casts.

=Color.= In estimating the color we must note the various shades of yellow, red and brown and compare these with the normal in different genera of animals, on different food and water, and in different conditions of health. Grades of color may be stated as follows:

=Yellow=: Pale, clear and deep yellows.

=Red=: Reddish yellow, yellowish red, and red.

=Brown=: Brownish red, reddish brown and brownish black.

=Color of Normal Urine.= This varies with the species of animal, food, quantity of water drunk, and time of retention in the bladder.

=Horse=: Urine is normally clear yellow, brownish yellow, or deep citron yellow, and the color is deepened by rich and abundant food (excess of solids) and by exposure to the air (changes in pigments). It may be sulphur white and sedimentary from precipitation of CaCO_{2} when on green food.

=Ox, Calf, Sheep and Goat=: Normal urine clear yellow to wine yellow. In the ox especially it is a pale straw tint, but varies to a deep brown on nitrogenous food (clover, peas, beans, cotton seed, lentils, pea or bean straw). Color may be due to indican and sometimes to indicanin or indigo blue, which explains the blue urine sometimes described.

=Dog=: Normal urine is yellow, straw colored, aniline yellow, honey yellow, to brownish yellow in hot season or on dry nitrogenous food. Is always relatively deeper than in ruminants.

=Cat=: Straw yellow to honey yellow, with variation as in the dog.

=Pig=: Very pale yellow, more highly colored on dry feeding, nuts, peas, etc.

=Birds=: White or yellow, sedimentary. Mixed with fæces in cloaca.

=Color of Pathological Urine=: =Pale yellow= with excessive secretion glycosuria, polyuria, cryptogamic polyuria, chronic interstitial nephritis, under diuretics, or after excessive drinking. The free secretion of a crisis in a fever is pale yellow.

=Deep yellow=, =deep red=, =deep brown color=, indicates excess of urinary pigment (urobiline) and is deepened by nitric acid. This is seen in all hyperthermias with suppressed or diminished secretion, in privation of water, or food. This urine is _acid_ even in herbivora.

=Yellow=, =saffron yellow=, =brownish yellow=, =greenish=, =olive=, =or brownish red= indicate the presence of bile pigments (biliverdin, bilirubin) as in jaundice or cholyuria. Bile salts should be tested for. A similar coloration may come from free consumption of carrots, or other yellow pigmentary matters.

=Red=, =brownish red=, =blood red=, =or deep brown color= implies the presence of blood or blood coloring matter in the urine (hæmaturia, hæmoglobinuria). Exposed to the air this becomes brown or chocolate in ratio with the amount of blood or blood pigment present. Some such cases are complicated by blood clots.

Color due to Foreign Constituents.

=Bronze or black color= may come from injection of =phenic acid=.

=Deep green or olive green= may come from =tar=, =carbolic acid=, =salol=, =creosote=, or =derivatives of benzine= taken in.

=Brownish green= comes from =thallin= and reddens with iron chloride.

=Brown or blood red= from =rhubarb= or =senna=.

=Purple red from santonin=, if alkaline (if acid, is reddish yellow).

=Red= from =madder= (it is alleged from indigo).

=Yellow= from =carrots=.

=Blue= (indigo blue) may occur in urine of horse or ox when exposed to the air.

=Bluish green= will come from feeding =indigo=.

=White or yellow color= will result from the presence of =pus=.