Chapter V: Muscles of the Leg and Foot (15)

1. The =lumbar lymph glands= (Lg. lumbales) lie along the course of the abdominal aorta and posterior vena cava (Fig. 450). Some are placed along the lower surface and sides of the vessels, others above. A few small glands may be found above the sublumbar muscles. The small nodes which are situated at the hilus of the kidneys are often termed the renal lymph glands. They receive afferent vessels from the lumbar wall of the abdomen and the paired viscera (kidneys, adrenals, genital organs), also the inguinal vessels and the efferents of the iliac glands. Their efferents go to the thoracic duct, constituting the lumbar trunks of origin of that vessel.

2. The =internal iliac lymph glands= (Lg. iliacæ internæ) are grouped about the terminal part of the aorta and the origins of the iliac arteries (Fig. 450). Their afferent vessels come chiefly from the pelvis, pelvic viscera, and tail, and they receive efferent vessels of the external iliac and deep inguinal glands.

3. The =external iliac lymph glands= (Lg. iliacæ externæ) form a group on either side on the iliac fascia at the bifurcation of the circumflex iliac artery (Fig. 450). Their afferent vessels come from the flank and abdominal floor, the outer surface of the thigh, and the precrural glands. The efferent vessels go to the lumbar and internal iliac glands.

4. The =sacral lymph glands= (Lg. sacrales) are small nodes situated along the borders of the sacrum and on its pelvic surface. They receive afferents from the roof of the pelvis and from the tail, and their efferent vessels pass to the internal iliac glands.

5. The =superficial inguinal lymph glands= (Lg. inguinales superficiales) lie on the abdominal tunic in front of the external inguinal ring (Fig. 457). They form an elongated group along the course of the subcutaneous abdominal artery, on either side of the penis in the male, above the mammary glands in the female; in the latter they are often termed =mammary=. Their afferents come from the inner surface of the thigh, the abdominal floor, the sheath and scrotum in the male, and the mammary glands in the female. The efferent vessels ascend through the inguinal canal and go to the deep inguinal and lumbar glands.

6. The =ischiatic lymph gland= (Lg. ischiadica) is a small node which may be found at the lesser sciatic notch. It receives lymph from the adjacent parts and from the popliteal glands, and sends efferents to the sacral and internal iliac glands.

The =visceral glands= include the following:

1. The =gastric lymph glands= (Lg. gastricæ) are situated along the course of the gastric arteries. Several occur along the attachment of the gastro-phrenic ligament. A group lies at the lesser curvature a short distance below the cardia. There is another small group on the visceral surface where the posterior gastric artery divides into its primary branches. Two or three small nodes are usually found on the ventral aspect of the pylorus. Other small glands are scattered along the course of the gastro-epiploic and short gastric arteries in the great and gastro-splenic omenta. The efferent vessels pass largely to the cœliac radicle of the thoracic duct, but along the left part of the great curvature they go to the splenic glands.

2. The =hepatic lymph glands= (Lg. hepaticæ) lie along the portal vein and hepatic artery and in the lesser omentum. Their efferent vessels go to the cœliac radicle of the cisterna chyli.

Many of the lymph vessels from the parietal surface of the liver pass
in the falciform and lateral ligaments to the diaphragm and anastomose
with its lymphatics. Some pass through the diaphragm with the vena
cava and go to the mediastinal glands.

The =pancreatic lymph vessels= follow the course of the blood-vessels which supply the gland; most of them go to the splenic and hepatic glands.

3. The =splenic lymph glands= (Lg. lienales) lie along the course of the splenic blood-vessels. Their afferent vessels come from the subscapular network of the spleen, from the greater curvature of the stomach, and from the left part of the pancreas. The efferents pass to the cœliac radicle of the thoracic duct.

4. The =mesenteric lymph glands= (Lg. mesentericæ) are situated in the great mesentery near its root. They are numerous and hence lie close together. They receive a very large number of afferent vessels (400 to 500) from the small intestine. They have several considerable efferents which concur in the formation of the intestinal radicles of the cisterna chyli.

The lymph vessels of the intestine form three sets of capillary
plexuses, viz., in the subserosa, submucosa, and mucosa. The lymph
follicles, solitary and aggregate, lie in the zone of the plexus of
the mucosa. The collecting vessels arise from the subserous plexus.

5. The =lymph glands of the cæcum= are numerous and are distributed along the course of the cæcal blood-vessels. Their efferents enter into the formation of an intestinal radicle of the cisterna chyli.

6. The =lymph glands of the great colon= are extremely numerous and are placed close together along the colic blood-vessels. Their efferent vessels are large and numerous. They converge to two large trunks which concur with those of the cæcum and small intestine to form an intestinal radicle of the cisterna chyli.

The intestinal radicles of the cisterna chyli are formed by the
confluence of efferents from the intestinal lymph glands. The anterior
trunk lies on the left side of the anterior mesenteric artery, passes
between that vessel and the cœliac artery, turns sharply backward
across the right renal vessels and opens into the cisterna. It is
formed by the union of the cœliac trunk with efferents from the glands
of the small intestine, cæcum and colon. It is about four inches (ca.
10 cm.) in length and is ampullate. The posterior trunk receives
vessels from the small intestine and small colon. It usually opens
into a trunk formed by the union of the right and left lumbar ducts.
It is usually ampullate at its termination (Franck). The arrangement
of these collecting trunks is, however, very variable.

7. The =lymph glands of the small colon= are situated in part on the wall of the bowel along the attachment of the mesentery, in part between the layers of the latter along the course of the blood-vessels. The efferent vessels go to the lumbar glands and to the posterior intestinal radicle of the thoracic duct.

The =lymph vessels of the rectum= pass chiefly to the lumbar and internal iliac glands.

8. The =anal lymph glands= (Lg. anales) form a small group on either side of the sphincter ani externus (Figs. 451, 453). They receive afferents from the anus, perineum, and tail. Their efferents go to the internal iliac glands.

THE LYMPH GLANDS AND VESSELS OF THE THORACIC LIMB

1. The =axillary lymph glands= (Lg. axillares), some ten to twelve in number, are grouped on the inner face of the distal part of the teres major and the tendon of the latissimus dorsi at the angle of junction of the external thoracic and subscapular veins with the brachial (Fig. 466). Their efferents include most of the lymph vessels of the limb, which come directly or as efferents from the cubital glands. They receive also lymph vessels from the thoracic wall. The efferents accompany the brachial blood-vessels and end in the prepectoral glands and the thoracic and right lymphatic ducts.

2. The =cubital lymph glands= (Lg. cubitales), usually eight to ten in number, form a discoid oval group at the inner side of the distal part of the shaft of the humerus (Figs. 441, 446). They lie behind the biceps muscle on the brachial vessels and median nerve and are covered by the deep fascia and the posterior superficial pectoral muscle. They receive as afferents most of the vessels from the limb below this point. Their efferents pass chiefly to the axillary glands, but in part to the prescapular glands also.

A number of superficial lymph vessels ascend with or near the subcutaneous veins (cephalic and accessory cephalic) and join the prescapular and prepectoral glands. Superficial vessels from the chest-wall and shoulder run across the latter to the prescapular glands. The superficial lymphatics of the pectoral region form a plexus which drains into the prepectoral and prescapular glands by a number of vessels which accompany the cephalic vein. The deep lymph vessels of the pectoral region run with the external thoracic vein to the axillary glands.

THE LYMPH GLANDS AND VESSELS OF THE PELVIC LIMB

1. The =precrural= or =subiliac lymph glands= (Lg. subiliacæ) are situated in the fold of the groin on the anterior border of the tensor fasciæ latæ, about midway between the point of the hip and the patella (Figs. 450, 451, 457). They lie on the course of the posterior branch of the circumflex iliac artery, and number usually about a dozen. They receive superficial lymph vessels from the hip, thigh, and flank. Their efferent vessels ascend with the posterior circumflex iliac vein, enter the abdomen near the external angle of the ilium, and join the external iliac lymph glands.

2. The =deep inguinal lymph glands= (Lg. inguinales profundæ) form a large group situated in the upper part of the femoral canal between the pectineus and sartorius muscles (Figs. 451, 457). They cover the femoral vessels and are related superficially to the inguinal ligament. They receive nearly all of the lymph vessels of the limb below them. Their efferent vessels ascend to the internal iliac glands.

3. The =popliteal lymph glands= (Lg. popliteæ), usually four to six in number, lie behind the origin of the gastrocnemius and between the biceps femoris and semitendinosus at the division of the posterior femoral artery into its primary branches (Fig. 455). They receive the deep lymph vessels of the distal part of the limb. Their efferent vessels chiefly follow the course of the femoral vessels to the deep inguinal glands, but one or two ascend in company with a vein along the great sciatic nerve and may enter a gland at the lesser sciatic notch. From this a vessel accompanies the internal pudic vein and joins the internal iliac glands.

Several superficial lymph vessels ascend with or near the internal
metatarsal and saphenous veins, enter the femoral canal, and end in
the deep inguinal glands.

THE FŒTAL CIRCULATION

The blood of the fœtus is oxygenated, receives nutrient matter, and gives off waste matter by close contiguity with the maternal blood in the placenta. The chief differences in the blood-vascular system as compared with that which obtains after birth are correlated with this interchange.

The =umbilical arteries=, right and left, are large vessels which arise from the internal iliac arteries and pass downward and forward in the umbilical folds of peritoneum on either side of the bladder to the umbilicus. Here they are incorporated with the umbilical vein and the urachus in the umbilical cord, ramify in the allantois, and end as the capillaries of the fœtal placenta. They conduct the impure blood to the placenta. After birth these vessels retract with the bladder to the pelvic cavity; their lumen becomes greatly reduced and the wall thickened so that they are cord-like and are termed the round ligaments of the bladder.

The =umbilical vein= receives the oxygenated blood from the placenta. Its radicles converge to form in the horse a single large trunk which separates from the other constituents of the umbilical cord on entering the abdomen and passes forward along the abdominal floor in the free border of the falciform ligament of the liver. It enters the latter at the umbilical fissure and joins the portal vein, so that the blood conveyed by it passes through the capillaries of the liver before entering the posterior vena cava.

In the ox and dog some of the blood in the umbilical vein is conveyed directly to the vena cava by the =ductus venosus= (Arantii). This vessel is given off within the liver from a venous sinus formed by the confluence of the portal and umbilical veins and passes directly to the posterior vena cava.

The =foramen ovale= is an opening in the septum between the atria, by which the latter communicate with each other. It is guarded by a valve (Valvula foraminis ovalis) which prevents the blood from passing from the left atrium to the right. After birth the foramen soon closes, but this part of the septum remains membranous, and there is a deep =fossa ovalis= in the right atrium which indicates the position of the former opening. In some cases the foramen persists to a variable extent in the adult without apparent disturbance of the circulation.

The =pulmonary circulation= is very limited in the fœtus, and most of the blood which enters the pulmonary artery passes through the =ductus arteriosus= to the aorta. This vessel is larger than the divisions of the pulmonary which go to the lungs and joins the left side of the aortic arch. After birth the pulmonary circulation undergoes promptly an enormous increase and the ductus is rapidly transformed into a fibrous cord—the =ligamentum arteriosum=.

The only arterial blood in the fœtus is that carried by the umbilical vein. This blood is mixed in the liver with the venous blood of the portal vein, and after passing through the capillaries of the liver is carried by the hepatic veins to the posterior vena cava. The latter receives also the venous blood from the posterior part of the trunk and the pelvic limbs. It is generally believed that the blood carried into the right atrium by the posterior vena cava passes largely, if not entirely, through the foramen ovale into the left atrium, while the blood flowing into it through the anterior vena cava passes into the right ventricle. On this basis the blood received by the left atrium consists chiefly of mixed blood from the posterior vena cava, since the small amount of blood conveyed by the pulmonary veins is venous. This mixed blood passes into the left ventricle and is forced into the systemic arteries. The venous blood from the anterior part of the body and the thoracic limbs is conveyed by the anterior vena cava to the right atrium, passes into the right ventricle, and is forced into the pulmonary artery. A small amount is carried to the lungs, but the bulk of it passes by the ductus arteriosus into the aorta behind the point of origin of the brachiocephalic trunk (anterior aorta), and is carried to the posterior part of the body, a large part passing by the umbilical arteries to the placenta.

THE BLOOD-VASCULAR SYSTEM OF THE OX

THE PERICARDIUM AND HEART

The =pericardium= is attached by two fibrous bands (Ligamenta sternopericardiaca) to the sternum opposite the facets for the sixth costal cartilages; these ligaments, right and left, are embedded in the mass of fat which separates the apex of the pericardium from the floor of the thorax.

FIG. 467.—HEART OF OX, LEFT VIEW.
]

The =heart= of the adult ox has an average weight of about 5½ to 6 pounds (ca. 2.5 to 2.7 kg.), or about 0.4 to 0.5 per cent. of the body-weight. Its length from base to apex is relatively longer than that of the horse and the base is smaller in both its diameters.

A shallow =intermediate groove= (Sulcus intermedius) extends from the coronary groove down the left side of the posterior border, but does not reach the apex. The amount of fat in and near the grooves is much greater than in the horse.

The heart is situated more to the left of the median plane than in the horse and is opposite to the third, fourth, and fifth ribs when it is contracted. It has extensive contact with the lateral wall of the thorax on the left side, but none on the right side, where a considerable thickness of lung covers the pericardium.[178]

Two bones, the =ossa cordis=, develop in the aortic fibrous ring. The right one is in apposition with the atrio-ventricular rings and is irregularly triangular in form. Its left face is concave and gives attachment to the right posterior cusp of the aortic valve. The right surface is convex from before backward. The base is superior. The posterior border bears two projections separated by a notch. It is usually a little more than an inch (ca. 4 cm.) in length. The left bone is smaller and is inconstant. Its concave right border gives attachment to the left posterior cusp of the aortic valve. There is a large fleshy moderator band in the right ventricle.

THE ARTERIES[179]

The great arterial trunks in the thorax resemble those of the horse in general disposition.

The =left coronary artery= is much larger than the right one; it gives off a branch which descends in the intermediate groove, and terminates by running downward in the right longitudinal groove. The =right artery=, after emerging from the interval between the right auricle and the pulmonary artery, divides into branches which are distributed to the wall of the right ventricle.

The =brachiocephalic trunk= (anterior aorta) is usually four or five inches (ca. 10 to 12 cm.) in length.

The =brachial arteries= give off in the thorax the following branches:

1. A common trunk for the subcostal, dorsal, superior or deep cervical, and vertebral arteries.

(1) The =subcostal artery= commonly arises separately, but may be given off as in the horse. It supplies the first three intercostal arteries.

(2) The =dorsal artery= is relatively small. It usually ascends in front of the first costo-vertebral joint and is distributed as in the horse.

(3) The =superior= or =deep cervical artery= may arise from a common stem (Truncus vertebro-cervicalis) with the vertebral, or may constitute a branch of that artery. It passes up between the first thoracic and last cervical vertebræ or between the sixth and seventh cervical and is distributed as in the horse.

(4) The =vertebral artery= passes along the neck as in the horse to the intervertebral foramen between the second and third cervical vertebræ, gives off a muscular branch, and enters the vertebral canal (Fig. 469). It runs forward on the floor of the canal—connected with its fellow by two or three transverse anastomoses—and divides in the atlas into two branches. The smaller internal division (cerebrospinal artery) passes forward to the floor of the cranium and concurs with the condyloid artery and branches of the internal maxillary in the formation of a large =rete mirabile=. The large external branch emerges through the intervertebral foramen of the atlas and ramifies in the muscles of the neck in that region, compensating for the smallness of the branches of the occipital artery. It also sends a branch to the rete mirabile. The collateral branches detached to the cervical muscles are large and compensate for the small size of the deep cervical artery. The collateral spinal branches of the vertebrals pass through the intervertebral foramina, divide into anterior and posterior branches, and form two longitudinal trunks which are connected by cross-branches so as to form irregular polygonal figures.

2. The =internal thoracic artery=.

3. The =inferior cervical artery= corresponds usually to the ascending branch of that vessel in the horse.

4. The =external thoracic artery= is large and usually gives off a branch which is equivalent to the descending branch of the inferior cervical artery of the horse.

THE COMMON CAROTID ARTERY

FIG. 468.—SCHEMA OF CHIEF ARTERIES OF HEAD OF COW.

_1_, Common carotid artery; _2_, thyro-laryngeal; _3_, thyroid; _4_,
laryngeal; _5_, pharyngeal; _6_, occipital; _7_, condyloid; _8_,
middle meningeal; _9_, pharyngeal; _10_, external maxillary; _11_,
lingual; _12_, sublingual; _13_, superior labial; _14_, internal
maxillary; _15_, masseteric; _16_, inferior alveolar; _17_,
buccinator; _18_, great palatine; _19_, sphenopalatine; _20_,
posterior auricular; _21_, superficial temporal; _22_, posterior
meningeal; _23_, anterior auricular; _24_, artery to matrix of horn;
_25_, deep temporal; _26_, arteries to rete mirabile; _27_, frontal;
_28_, malar; _28′_, dorsal nasal continuation of malar; _29_,
infraorbital; _29′_, lateral nasal continuation of _29_.
]

The =carotid arteries= usually arise from a common trunk about two inches (ca. 5 cm.) in length, but in exceptional cases are given off separately from the brachiocephalic. Each pursues a course similar to that of the horse and is accompanied by the small internal jugular vein, but is separated from the external jugular vein by the omo-hyoid and sterno-mastoid muscles. It divides at the digastricus into occipital, external maxillary, and external carotid arteries. In addition to tracheal, œsophageal, and muscular branches, it gives off the thyroid and laryngeal arteries. The =thyroid artery= (A. thyreoidea cranialis) bends around the anterior end of the thyroid gland, in which it ramifies. The accessory thyroid artery is usually absent. The =laryngeal artery= may arise with the thyroid.

1. The =occipital artery= is relatively small. It gives off:

(1) The =pharyngeal artery=, which, however, may arise from the external carotid.

(2) Several branches to the muscles (chiefly the flexors) and to the atlanto-occipital joint.

(3) The =condyloid artery= passes into the cranium through the anterior foramen in the condyloid fossa, and joins the vertebral in the formation of the rete mirabile about the pituitary gland. Before entering the cranium it gives off a branch to the pharyngeal lymph glands, and the middle meningeal artery; the latter passes through the foramen lacerum. Another branch enters the temporal canal and gives twigs to the temporalis muscle and the mucous membrane of the frontal sinus. A muscular branch emerges from the intervertebral foramen of the atlas. A diploic branch goes into the occipital condyle and squama, and emits twigs to the occipital muscles.

FIG. 469.—FLOOR OF CRANIUM AND ANTERIOR PART OF VERTEBRAL CANAL OF OX.

_1_, Vertebral artery; _2_, muscular branches of _1_; _3_, branches of
_1_ to the rete mirabile, _4_; _5_, branches of internal maxillary
artery to rete; _6_, branch of internal maxillary artery entering
cranium through foramen ovale; _7_, condyloid artery; _8_, emergent
artery from rete, distributed like internal carotid artery of horse;
_9_, _9′_, longitudinal vertebral sinuses; _a_, cribriform plate;
_b_, optic foramina; _c_, for. lacerum orbitale + rotundum; _d_,
foramen ovale; _e_, occipital condyle; _f_, _g_, _h_, first, second,
and third cervical vertebræ. (After Leisering’s Atlas.)
]

2. The =external maxillary artery= is smaller than that of the horse, but pursues a similar course. The =lingual artery= is large, and often arises separately from the common carotid; it gives off a branch to the submaxillary gland, and the =sublingual artery=. After turning around the jaw the facial gives off the two =labial arteries=. The =superior labial= is large; it usually gives off a branch which runs forward almost parallel with the lateral nasal. The =angular artery= is absent or rudimentary, and the =lateral= and =dorsal nasal arteries= spring from branches of the internal maxillary.

3. The =external carotid artery= passes upward between the stylo-hyoideus and the great cornu of the hyoid bone, turns forward across the external face of the latter, and divides into superficial temporal and internal maxillary arteries. It gives off the following collateral branches:

(1) Branches to the parotid and submaxillary glands.

(2) The =pharyngeal artery=, which, however, often arises from the occipital.

(3) The =posterior auricular=, which resembles that of the horse and sends a stylo-mastoid branch into the tympanum. It may arise from the superficial temporal.

(4) The =masseteric artery= resembles that of the horse, but is smaller.

The =superficial temporal artery= is large and presents the following special features: (1) Its transverse facial branch passes into the central part of the masseter. (2) It gives off a branch which corresponds to the posterior meningeal artery of the horse, enters the temporal canal, and ramifies in the dura mater, giving off twigs to the external ear, the temporal muscle, and the frontal sinus. (3) It usually gives off the anterior auricular artery. (4) Branches are supplied to the frontalis muscle and the eyelids, (5) A large branch passes around the outer side of the base of the horn-core, supplies the matrix of the horn, and anastomoses across the back of the frontal eminence with the artery of the opposite side.

The =internal maxillary artery= is less curved than in the horse and is entirely extraosseous, since the alar canal is absent. The principal differential features in its branching are as follows:

(1) The =ophthalmic artery= forms a rete mirabile within the periorbita. Its frontal branch enters the supraorbital canal and ramifies chiefly in the frontal sinus.

(2) Several branches take the place of the internal carotid artery. One of these enters the cranial cavity through the foramen ovale and several small ones pass through the foramen which represents the foramen rotundum and foramen lacerum orbitale of the horse. They concur with the vertebral and condyloid arteries in the formation of an extensive =rete mirabile= on the cranial floor around the sella turcica. From each side of the rete an artery arises which is distributed in general like the internal carotid of the horse.

(3) The =malar artery= is large; it arises by a common trunk with the infraorbital and gives off the =dorsal nasal= and the =angular artery of the eye=.

(4) The =infraorbital artery= is large and emerges from the infraorbital foramen to form the =lateral nasal artery=.

(5) The =palatine artery= is smaller than in the horse and usually arises by a common trunk with the sphenopalatine. It passes through the palatine canal and along the palatine groove, enters the nasal cavity through the incisive fissure, and does not go to the upper lip. It forms a rete mirabile about the naso-palatine canal and terminates in the mucous membrane of the anterior part of the nasal cavity.

ARTERIES OF THE THORACIC LIMB

The =brachial artery= pursues the same course in the arm as that of the horse. At the elbow it becomes the median.[180] The chief differential features in its branches are as follows:

1. The =subscapular artery= is almost as large as the continuation of the brachial. The =posterior circumflex artery= sends branches backward and downward into the triceps, taking the place in part of the deep brachial artery. The =thoracico-dorsal artery= supplies branches to the pectoral muscles and the triceps as well as the teres major and latissimus dorsi; it may arise directly from the brachial.

2. The =deep brachial artery= is small.

3. The =superior collateral ulnar artery= is often double, and does not extend to the carpus.

The =median artery= (posterior radial artery) descends along the inner part of the posterior surface of the radius and divides near the middle of the forearm into the radial and ulnar arteries. It gives off at the upper third of the forearm the =common interosseous artery=, a large vessel which anastomoses with the deep brachial, passes through the proximal interosseous space, and descends (as the dorsal interosseous) in the groove between the radius and ulna, and concurs in the formation of the rete carpi dorsale. At the distal end of the forearm it sends a branch through the distal interosseous space, which passes downward, assists in forming the rete carpi volare, and is continued in the metacarpus as the external deep volar metacarpal artery. This is a small vessel which passes down under the outer border of the suspensory ligament and assists in forming the deep volar arch near the fetlock.

FIG. 470.—ARTERIES OF DISTAL PART OF RIGHT FORE LIMB OF OX, ANTERIOR
VIEW.

_a_, Interosseous artery; _b_, dorsal branch of radial artery; _c_,
rete carpi dorsale; _d_, dorsal metacarpal artery; _e_, dorsal
common digital artery; _f_, _f_, dorsal proper digital arteries.
]

FIG. 471.—ARTERIES OF DISTAL PART OF RIGHT FORE LIMB OF OX, POSTERIOR
VIEW.

_g_, Ulnar artery; _h_, radial artery; _i_, volar branch of common
interosseous artery; _k_, _l_, _m_, deep volar metacarpal arteries;
_A.v._, volar arches; _n_, volar common digital artery; _o_, _o′_,
_p_, volar proper digital arteries.
]

The =radial artery= is smaller than the ulnar. It descends on the flexor carpi internus, passes over the postero-internal surface of the carpus, and is continued as the internal deep volar metacarpal. At the distal end of the forearm and at the carpus it furnishes branches to the retia carpi. Another branch (A. met. perforans proximalis) runs outward between the suspensory ligament and the large metacarpal bone, passes through the proximal foramen of the bone, and unites with the interosseous artery; before passing through the foramen it detaches the middle deep volar metacarpal artery (A. met. volaris prof. III.), which descends on the posterior face of the metacarpal bone, receives an anastomotic branch from the internal deep artery, and concurs in the formation of the deep volar arch above the fetlock.

The =ulnar artery=, the larger of the two divisions of the median, descends under cover of the flexor carpi internus without giving off any large branches in the forearm. It passes through the carpal canal and continues along the inner side of the deep flexor tendon as the =volar common digital artery=. At the distal third of the metacarpus this vessel is joined by a branch from the internal deep volar metacarpal artery, forming the superficial volar arch. Near this another branch of the common digital (or of the internal digital) passes around the outer border of the flexor tendons to the posterior face of the metacarpal bone and concurs with the deep volar metacarpal arteries in the formation of the deep volar arch. A branch from the arch passes forward through the inferior foramen of the metacarpal bone and joins the dorsal metacarpal artery which descends from the rete carpi dorsale in the anterior metacarpal groove.

The =volar common digital artery= (A. metacarpea volaris superficialis III.) passes into the interdigital space and divides into two =volar proper digital arteries=, which descend along the interdigital surfaces of the chief digits and pass through the foramina at the upper part of the interdigital surfaces of the third phalanges, enter the cavities in these bones, and ramify in a manner similar to the corresponding vessels in the horse. The volar common digital detaches a branch (A. interdigitalis perforans) which passes forward through the upper part of the interdigital space and anastomoses with the dorsal metacarpal artery.

The volar proper digital arteries (or the common digital) give off, in
addition to other collaterals, branches which correspond to the
arteries of the plantar cushion of the horse. These pass to the bulbs
of the claws and anastomose with each other and with the inner and
outer digital arteries, forming an arch from which numerous branches
are distributed to the matrix of the hoofs.

The =dorsal metacarpal artery= (A. met. dorsalis III.) is a small vessel which arises from the rete carpi dorsale, descends in the groove on the anterior face of the metacarpal bone, and is joined by the inferior perforating metacarpal artery from the deep volar arch to constitute the dorsal common digital artery. This vessel (A. digitalis communis dorsalis III.) divides into two =dorsal proper digital arteries=.

The =internal digital artery= (A. digiti III. medialis) is the continuation of the internal deep volar metacarpal artery. It descends on the inner side of the inner digit and terminates at the bulb of the claw by anastomosing with the corresponding volar proper digital artery. It gives off a branch to the rudimentary digit and forms a transverse anastomosis behind the first phalanx with the volar common digital or its inner division.

The =external digital artery= (A. digiti IV. lateralis) arises from the deep volar arch, passes down on the outer side of the external digit and is distributed like the inner one.

BRANCHES OF THE THORACIC AORTA

The =bronchial= and =œsophageal= arteries often arise separately.

Ten pairs of =intercostal arteries= usually arise from the aorta. The other three come from the subcostal artery.

The two =phrenic arteries= are very variable in origin. They may come from the aorta, the cœliac, left ruminal, or an intercostal or lumbar artery.

BRANCHES OF THE ABDOMINAL AORTA

The =cœliac artery= is about four to five inches (ca. 10 to 12 cm.) in length. It passes downward and curves forward between the rumen and pancreas on the left and the right crus of the diaphragm and the posterior vena cava on the right. It gives off five chief branches.

1. The =hepatic artery= arises from the convex side of the curve of the cœliac artery as it crosses the posterior vena cava. It passes downward, forward, and to the right above the portal vein to the portal fissure, and gives off the following branches:

(1) Pancreatic branches.

(2) Dorsal and ventral branches to the liver. The ventral branch is the larger; it gives off the right gastric artery, which runs in the lesser omentum to supply the origin of the duodenum and the pylorus, anastomosing with the dorsal branch of the omaso-abomasal artery.

(3) The cystic artery supplies the gall-bladder.

(4) The gastro-duodenal artery divides into right gastro-epiploic and pancreatico-duodenal branches. The right gastro-epiploic artery anastomoses with the left gastro-epiploic. The pancreatico-duodenal artery anastomoses with the first intestinal branch of the anterior mesenteric artery.

2. The =right ruminal artery= (A. ruminalis dextra) is the largest branch, and usually arises by a short common trunk with the splenic. It runs downward and backward on the right face of the dorsal sac of the rumen to the posterior transverse fissure, in which it turns around to the left and anastomoses with branches of the left ruminal artery. It gives off a pancreatic branch, dorsal and ventral coronary arteries, branches to the great omentum, and ramifies on both surfaces of the rumen.

3. The =left ruminal artery= (A. ruminalis sinistra) runs downward on the anterior part of the right face of the rumen, enters the anterior furrow, in which it runs from right to left, and continues backward in the left longitudinal groove, anastomosing with branches of the right artery. It supplies chiefly the left face of the rumen, but not its posterior part. It usually gives off near its origin the =reticular artery= (A. reticularis); this rather small vessel passes forward on the dorsal curvature of the rumen and turns downward in the rumino-reticular groove, in the bottom of which it runs around ventrally to the right side. It gives off a branch which passes to the left of the cardia and along the lesser curvature of the reticulum to the neck of the omasum. The reticular branches anastomose with the omaso-abomasal and left ruminal arteries.

4. The =omaso-abomasal artery= (A. gastrica sinistra) appears as the continuation of the cœliac. It passes forward and downward to the greater curvature of the omasum and divides after a course of four or five inches into two branches. The =dorsal branch= curves sharply backward on the dorsal surface of the omasum, continues along the lesser curvature of the abomasum, and anastomoses with the hepatic artery. It supplies branches to the omasum and to the lesser curvature and pyloric part of the abomasum. The =ventral branch= (A. gastroepiploica sinistra) runs forward and downward over the anterior extremity of the omasum, passes backward in the great omentum close to the ventral curvature of the abomasum, and anastomoses with the right gastro-epiploic. A considerable branch from it curves around in front of the neck of the omasum to communicate with the reticular artery. Another branch runs back across the left side of the omaso-abomasal junction, and a third goes to the lesser (ventral) curvature of the omasum.

5. The =splenic artery= usually arises by a common trunk with the right ruminal artery. It passes forward and to the left across the dorsal curvature of the rumen and enters the hilus of the spleen.

The =anterior mesenteric artery= arises from the aorta just behind the cœliac, and has about the same caliber as the latter. It passes downward and a little to the right, and crosses the colon as it emerges from the spiral to run backward. After detaching twigs to the pancreas it gives off in succession the following branches:

1. A branch (A. colica media) passes to the colon as it emerges from the spiral arrangement. This artery is comparable to the middle colic or artery of the small colon of the horse; it runs backward along the terminal part of the colon, which it supplies.

FIG. 472.—GASTRIC ARTERIES OF OX, RIGHT VIEW (PARTLY SCHEMATIC).

_1_, Cœliac artery; _2_, right ruminal; _3_, splenic; _4_, reticular;
_5_, left ruminal; _6_, omaso-abomasal; _7_, dorsal branch of _6_;
_8_, ventral branch of _6_ (= left gastro-epiploic); _A_, dorsal sac
of rumen; _B_, ventral sac of rumen; _C_, _C_, posterior blind sacs;
_D_, œsophagus; _E_, reticulum; _F_, omasum; _G_, abomasum; _H_,
duodenum; _I_, right longitudinal furrow of rumen. By an oversight
the reticular artery is shown as arising from the omaso-abomasal.
]

FIG. 473.—GASTRIC ARTERIES OF OX, LEFT VIEW (PARTLY SCHEMATIC).

_1_, Left ruminal artery; _2_, continuation of right ruminal artery;
_3_, reticular artery, which disappears into rumino-reticular
groove; _A_, dorsal sac of rumen; _B_, ventral sac of rumen; _C_,
_C_, posterior blind sacs; _D_, œsophagus; _E_, reticulum; F,
rumino-reticular groove; _G_, left longitudinal furrow of rumen.
]

2. The ileo-cæco-colic artery ramifies on the right face of the spiral part of the colon. It gives off the ileo-cæcal artery, which divides into ileal and cæcal arteries.

3. An artery (Ramus collateralis) runs in the mesentery in a curve along the ventral border of the coils of the colon. (This vessel is absent in the sheep.)

4. An artery which constitutes the direct continuation of the anterior mesenteric pursues a course in the mesentery corresponding to the series of mesenteric lymph glands.

FIG. 474.—PLAN OF BRANCHES OF ANTERIOR MESENTERIC ARTERY OF OX.

_1_, Anterior mesenteric artery; _2_, middle colic artery; _3_,
ileo-cæco-colic artery; _4_, ramus collateralis; _5_, continuation
of anterior mesenteric artery, giving off branches to small
intestine; _6_, cæcal artery; _7_, colic branch of posterior
mesenteric artery; _A_, termination of duodenum.
]

The two preceding vessels are essentially the arteries of the small intestine, which they supply with the exception of its initial and terminal parts. The first gives off no considerable branches in its course along the ventral border of the coils of the colon, but on curving upward along the latter it anastomoses with the second artery and detaches numerous branches to the small intestine which form series of superposed anastomotic arches. It supplies, roughly speaking, about one-third of the small intestine and terminates by joining the ileal artery. The second artery gives off numerous branches which also form arches and supply about the first two-thirds of the small intestine, exclusive of the small part supplied by branches of the cœliac artery. Both arteries give branches to the lymph glands.[181]

The =posterior mesenteric artery= arises from the aorta near its termination. It is small and supplies branches to the terminal part of the colon and to the rectum.

The =renal arteries= arise from the aorta close together. The right one passes outward and forward across the dorsal face of the posterior vena cava to the hilus of the kidney. The left one runs backward, but necessarily varies in direction in conformity with the position of the kidney (_q. v._).

The =spermatic arteries= resemble those of the horse.

The =utero-ovarian arteries= are small.

The five pairs of =lumbar arteries= derived from the aorta are distributed much as in the horse. The sixth usually comes from the internal iliac artery.

FIG. 475.—PELVIC ARTERIES OF COW.

Part of the right wall of the uterus and vagina is removed and the
cervix uteri is shown in sagittal section. _a_, Aorta; _b_,
utero-ovarian artery; _b′_, ovarian, and _b″_, uterine branch of
_b_; _c_, external iliac artery; _d_, right internal iliac artery;
_e_, common trunk of umbilical artery (_e′_) and middle uterine
artery (_f_); _g_, ilio-lumbar artery; _h_, anterior gluteal
arteries; _i_, middle hæmorrhoidal artery; _k_, posterior uterine
artery; _l_, perineal artery; _m_, posterior gluteal artery; _n_,
obturator arteries; _o_, artery of clitoris; _p_, posterior
mesenteric artery; _r_, anterior hæmorrhoidal artery; _s_, middle
sacral artery; _1_, ovary; _2_, apparent body of uterus, really
apposed horns; _2′_, cornu; _3_, vagina; _4_, cervix uteri; _4′_,
vaginal part of uterus (os uteri); _5_, _5′_, broad ligaments, large
part of right one removed; _6_, urinary bladder; _7_, rectum; _8_,
sacrum; _9_, symphysis pelvis. (After Zieger.)
]

The =middle sacral artery= is a vessel about 5 mm. in diameter which continues the aorta. It arises from the dorsal face of the aorta at the angle of divergence of the internal iliacs, runs backward on the pelvic surface of the sacrum a little to the left of the median line, and is continued as the middle coccygeal artery. It gives off small collateral branches to the spinal cord and the muscles of the tail and the =lateral coccygeal arteries=. The latter may have a common trunk of origin, and each divides into dorsal and ventral branches. The =middle coccygeal artery= runs through the ventral (hæmal) arches of the coccygeal vertebræ. The coccygeal arteries are connected at pretty regular intervals by segmental anastomoses.

The =internal iliac arteries= are much longer than in the horse. Each passes backward on the sacro-sciatic ligament and divides about the middle of the pelvic wall into posterior gluteal and internal pudic branches. The chief differences in its distribution are: (1) A large trunk gives origin to the umbilical and middle uterine arteries. The =umbilical artery= is usually largely obliterated and its terminal branches receive their blood through anastomoses with the internal pudic. It gives off near its origin two small vessels, the ureteral artery (A. ureterica) and the deferential artery (A. deferentialis), which accompany the ureter and the vas deferens respectively. The =middle uterine artery= (A. uterina media) is very large. It is distributed chiefly to the cornu of the uterus, and compensates for the small size of the utero-ovarian artery. (2) The =ilio-lumbar= artery is relatively small and is distributed chiefly to the sublumbar muscles. It is sometimes replaced by branches of the circumflex iliac and gluteal arteries. (3) The =anterior gluteal artery= is commonly represented by several vessels. (4) The =obturator artery= is represented by several small branches which supply the obturator and adductor muscles. (5) The =iliaco-femoral= and =lateral sacral arteries= are absent. The absence of the latter is compensated by the middle sacral and gluteal arteries. (6) The =posterior gluteal= (or ischiatic) artery is large. It emerges through the lesser sciatic notch and ramifies in the biceps femoris and adjacent muscles. (7) The =internal pudic artery= (A. urethro-genitalis) is the direct continuation of the internal iliac. It gives off branches to the rectum, bladder, urethra, and genital organs. In the male it supplies the accessory genital glands and divides into dorsal and deep arteries of the penis; the a. dorsalis penis runs along the dorsum penis to the glans and gives twigs to the prepuce; the a. profunda penis gives off a perineal branch and enters the corpus cavernosum penis. In the female it gives off a large posterior uterine artery, which supplies the posterior part of the uterus and gives branches to the vagina and bladder. It ends as the a. clitoridis, which supplies the clitoris and adjacent parts.

ARTERIES OF THE PELVIC LIMB

The =external iliac artery= has the same course as in the horse. The circumflex iliac artery is large. A branch from it emerges between the abdominal and lumbar muscles near the external angle of the ilium and ramifies like the terminals of the ilio-lumbar artery of the horse.

The =femoral= and =popliteal arteries= pursue a similar course to those of the horse. The chief differences in their branches are as follows:

1. The =external pudic artery= is distributed chiefly to the scrotum in the male. In the cow it is usually termed the =mammary= and is very large, especially during lactation. Each divides at the base of the mammary gland into two branches which are distributed to the anterior and posterior parts (“quarters”) of the gland. A small branch accompanies the subcutaneous abdominal vein to the xiphoid region.

2. The =deep femoral artery= gives off an obturator branch which passes up through the obturator foramen to supply the obturator internus and compensates otherwise for the absence of the obturator artery.

3. The =anterior femoral artery= is large. It often gives off the =external circumflex artery= of the thigh, which perforates the proximal end of the quadriceps, gives branches to that muscle, the iliacus, glutei, and tensor fasciæ latæ.

4. The =saphenous artery= is large. It descends in front of the homonymous vein to the postero-internal surface of the hock, where it divides into two plantar branches. The =internal plantar artery= (A. plantaris medialis) is the direct continuation of the saphenous. It descends at first along the inner border of the superficial flexor tendon and is continued as the =internal superficial plantar metatarsal artery= along the inner side of the deep flexor tendon with the internal plantar nerve. It anastomoses at the proximal end of the metatarsus with the perforating metatarsal artery, assisting in the formation of the proximal plantar arch. Near the fetlock it concurs with the perforating branch of the dorsal metatarsal artery in the formation of the distal plantar arch. Below this it is continued as the =internal digital artery=. The =external plantar artery= (A. plantaris lateralis) is small. It descends along the outer border of the deep flexor tendon with the external plantar nerve, concurs with the perforating tarsal and the internal plantar arteries in the formation of the proximal plantar arch, and gives branches to the rete tarsi dorsale. Continuing downward along the deep flexor tendon as the =external superficial plantar metatarsal artery=, it assists in forming the distal plantar arch and becomes the =external digital artery=.

FIG. 476.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF OX, ANTERIOR
VIEW.

_a_, Anterior tibial artery; _b_, proximal perforating metatarsal
artery; _c_, dorsal metatarsal artery; _d_, dorsal common digital
artery; _e_, _e′_, dorsal proper digital arteries.
]

FIG. 477.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF OX, POSTERIOR
VIEW.

_e_, Saphenous artery; _f_, _f′_, internal and external plantar
arteries; _g_, _g′_, internal and external superficial plantar
metatarsal arteries; _h_, deep plantar metatarsal artery; _i_, _j_,
internal and external plantar digital arteries; _k_, plantar common
digital artery; _l_, _l′_, internal and external plantar digital
arteries.
]

The =posterior tibial artery= is relatively small and is distributed chiefly to the muscles on the posterior surface of the tibia. Lower down it is replaced by the saphenous artery as described above.

The =anterior tibial artery= has the same course as in the horse. It is continued down the groove on the front of the metatarsal bone as the =dorsal metatarsal artery=. This is the chief artery of the region and is accompanied by two veins. It detaches the proximal perforating metatarsal artery, which passes through the proximal foramen of the metatarsal bone and concurs with the superficial plantar arteries in forming the proximal plantar arch. Near the distal end of the metatarsal bone it gives off the distal perforating metatarsal artery which passes back through the distal metatarsal foramen and assists in forming the distal plantar arch. The two arches are connected by the small =deep plantar metatarsal artery= which lies in the groove on the posterior face of the large metatarsal bone.

The =dorsal common digital artery= is the direct continuation of the dorsal metatarsal. It divides into two branches which unite in the interdigital space with the corresponding branches of the plantar common digital to form the proper digital arteries.

The =plantar common digital artery= descends from the distal plantar arch, anastomoses in the interdigital space with the internal and external digitals, and divides into two branches which join those of the dorsal common digital artery as before mentioned.

The foregoing is a brief statement of the more common arrangement of the vessels in the distal part of the limb, but minor variations are very common.

THE VEINS[182]

The =vena hemiazygos= usually takes the place of the vena azygos. It lies along the left side of the aorta and the bodies of the thoracic vertebræ, turns down across the left face of the aorta and left pulmonary artery, runs back over the left auricle and opens into the great coronary vein or the right atrium. It receives the intercostal veins.

Two =jugular veins= occur on either side. The =internal jugular vein= (V. jugularis interna) is a relatively small vessel which accompanies the carotid artery. It arises by occipital, laryngeal, and thyroid radicles, receives tracheal, œsophageal, and muscular branches, and joins the external jugular near its termination. It is sometimes absent, but in some cases it appears, on the other hand, to be large enough to interfere with venesection practised on the external jugular. The =external jugular vein= (V. jugularis externa) is very large and corresponds to the single jugular of the horse. It is separated from the carotid artery in the greater part of its course by the sterno-cephalicus and omo-hyoideus muscles.

The =inferior cerebral vein= usually does not unite with the occipital; the latter is continued by the internal jugular vein.

The =orbital veins= form a network between the periorbita and the muscles of the eyeball. This plexus communicates with the cavernous sinus and with the superior cerebral vein. It is also drained by the =frontal vein= which runs in the supraorbital canal and groove and joins the angular vein of the eye.

The =dorsal nasal vein= is usually double.

The =superior labial vein= usually joins the infraorbital.

The =vena reflexa= is absent and the radicles which are received by it in the horse go to the internal maxillary vein.

The =sublingual vein= is very large.

The =veins of the thoracic limb= differ chiefly in the distal part; the special features are as follows:

The =dorsal digital veins= ascend on the front of the digits and are connected with the other digital veins by transverse branches. They unite near the fetlock to form the =dorsal metacarpal vein=. This runs upward on the anterior face of the metacarpus and carpus, inclines to the inner surface of the radius, and joins the accessory cephalic or the cephalic vein.

The =volar digital veins= are larger than the dorsal. They lie on the interdigital surfaces of the digits and unite in the interdigital space to form a trunk which is a satellite of the volar common digital artery.

The =internal= and =external digital veins= lie in front of the corresponding arteries. They are connected with the volar digital vein by a large branch which passes between the flexor tendons and the first phalanx. At the distal end of the metacarpus each inclines forward and anastomoses with the volar common digital vein to form the volar venous arch. The inner vein is continued as the internal volar metacarpal vein along the inner border of the suspensory ligament, and becomes a satellite of the radial artery in the forearm, while the outer one is continued on the posterior face of the metacarpal bone by two irregular veins, the external and middle volar metacarpals. The latter anastomose freely with each other and with the inner vein. They unite below the carpus or join the volar common digital vein.

The =accessory cephalic vein= is the upward continuation of the dorsal metacarpal vein and is much larger than in the horse.

The =posterior vena cava= is partially embedded in the medial border of the liver. Its abdominal part has a thicker wall than in the horse. Its affluents correspond to the arteries of which they are satellites. The =renal veins= are large and thick-walled; they run obliquely forward and join the vena cava at an acute angle. The left one is much the longer.

Two =middle sacral= veins usually accompany the artery.

The =veins of the mammary glands= deserve special notice. They converge to a venous circle at the base of the udder, which is drained chiefly by two pairs of veins. The =subcutaneous abdominal vein= (anterior mammary or “milk” vein) is very large in animals of the dairy breeds and its course along the ventral wall of the abdomen is easily followed. It is usually flexuous. It emerges at the anterior border of the udder about two or three inches (ca. 5 to 8 cm.) from the linea alba, runs forward (deviating a little outward), dips under the panniculus, passes through a foramen in the abdominal wall about a handbreadth from the median plane, and joins the internal thoracic vein. The =external pudic vein= (middle mammary vein) is also of considerable size. It ascends in the inguinal canal as a satellite of the artery and joins the external iliac vein. The right and left veins are connected at the posterior border of the base of the udder by a large transverse branch. From the latter arises the =perineal vein= (posterior mammary vein), which runs medially upward and backward to the perineum, turns around the ischial arch, and joins the internal pudic vein. In the male these veins are relatively small.

The deep veins of the thigh and leg resemble those of the horse, but there is no recurrent tibial vein.

The =saphenous vein= is much smaller than in the horse.

The =recurrent tarsal vein= (external saphenous) is large. It is the upward continuation of the external plantar metatarsal vein and anastomoses with the anterior tibial and saphenous veins. It arises on the outer face of the hock, ascends at first in front of the tendo Achillis, then crosses the latter externally, passes up between the biceps femoris and semitendinosus, and joins the posterior femoral vein.