Chapter XII: Epilogue: 351 (6)

The intellectual atmosphere in which scientific specialism arose was that of the so-called ‘Utilitarian Philosophy’. Many of the dicta of that school, which came into prominence toward the end of the eighteenth century, are still used as part of the language of men of Science and others. ‘The greatest happiness of the greatest number’ is a formula launched upon our common speech by Joseph Priestley (1733-1804, p. 154). The pursuit of such happiness as the main object of human activity is taught by the ‘Utilitarian’ philosophy, a word coined by the English political and social thinker, Jeremy Bentham (1748-1832). To Bentham, the founder of that philosophy, we owe such useful additions to our language as ‘codification’ and ‘international’, and these, together with ‘utilitarian’, give us some clue to the character and mode of his thought. It is probable that no thinker had a larger share than Bentham in ushering in the era of the subdivision of the sciences.

Bentham made a sustained attempt to draw a parallel between the physical and the social sciences, and this gave him a special influence over medical thinkers and especially over those that dealt with the public health. His pupil, John Stuart Mill (1806-73), speaks of his master’s mode of working as ‘the chemical method’. It is thus not remarkable that Bentham should exert a profound influence on Medicine, both directly and indirectly. The peculiarly logical, uncompromising and perhaps un-English character of his mind, while it prevented him, fortunately for himself, from taking an active share in the task of government, did not prevent him from influencing those who did. Specifically, he is the direct begetter of our modern system of organization of the Science of Preventive Medicine.

FIG. 95. A CARTOON OF THE EARLY NINETEENTH CENTURY illustrating the condition of children in the factories of the time. A bale is directed to Sir Robert Peel. This is the first Baronet (1750-1830), father of the statesman. Peel the elder was a cotton-spinner who imported from the London workhouses deserted children whom he treated well, but used to work his factories in Lancashire. He was a Member of Parliament and in 1802 carried the Act which was the forerunner of all factory legislation, _An Act for the Preservation of the Health and Morals of Apprentices and others, employed in Cotton and other Mills_.

]

§ 2. _The Revolution in Preventive Medicine._

Of all the many changes in Medicine and Medical thought that the Period of Scientific Subdivision has witnessed, none have been more revolutionary than those in the department which deals with Preventive Medicine. Great and important reforms were introduced during the course of the eighteenth century. These, however, even when the result of legislation, were the outcome of the effort of individuals, or were concerned with the Army and Navy (p. 169). In the period that follows, the Public Health becomes a general political, legislative, and administrative matter, and ‘Prevention’ becomes its watchword. The public consciousness--moralists will call it the public _conscience_--had been aroused, and has never again entirely slept. The chief agent in the awakening process, the intellectual force at its back, was and is Jeremy Bentham.

Rational Medicine has, in general, no national frontiers. To it men of all the national units have made important contributions. But the care of the Public Health in the period on which we now enter, being an affair of legislation and administration, has developed along national lines and it is difficult to discuss it save on a national basis. It is a source of justifiable national pride that Britain has, from the first and throughout, been the leader of the Public Health movement. But while we lose little and gain much by telling the story from the British point of view, it has still to be remembered that, just as Rational Medicine has, fortunately, no spiritual frontiers, so, unfortunately, sickness and suffering have no physical frontiers. Epidemics pass the most scientifically constructed boundaries upon the surface of the map, and without a passport. In our time this evident proposition has obtained, at least, formal recognition. International health legislation has at last appeared. A future historian of Rational Medicine will be able to write his chapter on the Public Health from the point of view of Humanity at large. The historian who has the misfortune to be born too early must still content himself with treating the subject along national lines.

(a) _Preventive Medicine in Britain._

If Bentham be the spiritual father of Public Health legislation, the protagonists whose names must be associated with the development of the movement along practical lines in England are Thomas Southwood Smith (1788-1861) and Edwin Chadwick (1800-90).

Thomas Southwood Smith was a Unitarian minister, and long combined this office with that of physician. Settling in London in 1820 he came under the influence of Bentham. By his essay on _The Use of the Dead to the Living_ he did something to remove the odium attached to dissection. The scandals of the time and the common sense of the ‘utilitarians’ (p. 190) led to the passing of the Anatomy Act of 1832. Thus by a proper legal process bodies became available for dissection by medical students. Bentham died just before this Act became law and by his will left his body to Southwood Smith to be the subject of dissection and of an anatomical lecture.

Southwood Smith’s services to the spread of interest in Public Health were very numerous. He circulated a simple and popular _Philosophy of Health_ (1835). He served on a board of inquiry as to the condition of children in factories (1832, cp. Fig. 191), and he was especially useful to the Poor Law Commissioners by reason of his exceptional knowledge of fevers. He was the founder of a ‘Health of Towns Association’ (1840), and of another association for ‘improving the Dwellings of the Industrial Classes’ (1842). In 1848 he became a member of a new government department, the ‘General Board of Health’ (p. 195). His official reports on Quarantine (1845), Cholera (1850), Yellow Fever (1852), and on the results of sanitary improvement (1854), were of world-wide use.

Edwin Chadwick (1800-90), who was not a medical man, introduced to public notice what he called the ‘sanitary idea’, a conception that colored the whole of his extraordinarily active life. He sat on Government Commissions on Poor Law, on Police, and on the investigation of the condition of factory children. One of his Reports (1833), issued while he and the century were both in the early thirties, recommended a system of inspection with a view to limiting children’s hours of work. The current system of pensions and of trade instruction to soldiers and sailors is the descendant of a scheme of Chadwick’s devising. An item in the evidence attached to one of his Reports is the public provision of open spaces for recreation, a topic of current interest at the moment of writing.

At the time of the accession of Queen Victoria in 1837 Chadwick was agitating for the appointment of a Sanitary Commission. Two years later, as a result of a grave epidemical outbreak in London, the Commission was appointed. Its reports, which drew wide attention at the time, have had a large share in determining the general course of health legislation in the ninety years that have since elapsed. The scientific basis of health legislation can only be determined if proper vital statistics be available. The Registration Act of 1838, under a developed form of which we still live and die, was in essence his work. If we search into the history of any department of the scientific treatment of the Public Health, we shall always ultimately work back either to Southwood Smith or to Chadwick and through them to Bentham.

Among the most important documents for which Chadwick was responsible was the _Parliamentary General Report on the Sanitary Condition of the Labouring Population of Great Britain_ (1842). It came to fruit in 1848 with the _Public Health Act_, which established a new governmental department, the ‘General Board of Health’ (p. 196). The same year saw the passage of the _Nuisances Removal and Diseases Prevention Act_, by which summary action in such matters was rendered possible on the complaint of specially authorized local authorities. Just as the Board came into action there was an outbreak of Cholera in England, of which 54,000 persons died. The statistics available under the new system made possible the deduction that the infection is conveyed by drinking-water and led to suitable precautions. This is one of the many instances in which the practice of prevention of a germ-borne disease preceded any knowledge of its organic cause, or indeed any direct knowledge of disease germs at all.

The first town in England to appoint a Medical Officer of Health was Liverpool. The City of London followed in 1848, when Simon took office. After Southwood Smith and Chadwick, Sir John Simon (1816-1904) was the foremost figure in the history of the Public Health of this country. He later became medical officer to the ‘General Board of Health’. The work of this Board--together with its medical officer--was taken over, for political and administrative reasons, by the Privy Council. The medical department of the Privy Council became in 1871 part of the Local Government Board, the medical functions of which were absorbed by the new Ministry of Health in 1917.

To Simon are due the abolition of urban cesspits and improvement of the system of sewers, and the institution of sanitary inspectors and legislation concerning housing and overcrowding. One important result of these measures was that it became possible to abandon the cruel and wasteful system of quarantine that had been of value in the eighteenth century. Simon’s plan, which was gradually adopted, was to trust to the same preventive methods for foreign as for native infections. This was, of course, only possible with an efficient sanitary service such as he succeeded in instituting. Such measures were aided by laboratory investigations, begun by a small staff. At first largely occupied with examinations in connection with actual outbreaks, its scientific functions rapidly grew. Working on a wider basis, these functions have been performed for the nation since 1911 under the direction of the Medical Research Council.

It will be seen that the curve begins definitely to take a downward trend about 1870. It has been falling ever since. It is now less than half of what it was sixty years ago. This fall is largely, though not entirely, due to decrease in infant mortality. Some of the more important epidemics are indicated. Typhus disappears as an important cause of death in the forties and Cholera and Small-pox in the sixties. Since then the death-rate has been considerably influenced by Influenza outbreaks.

]

(b) _Preventive Medicine in the United States._

In the United States the history of the national Public Health Service has been very different from that of the English system. The same philosophical tendencies have been at the basis of the American as of the English system. In the United States, however, the National Service has been linked with the Army and Navy in a manner quite foreign to British traditions. The Federal health system had its origin in the old Marine Hospital Service, first authorized by Congress in 1798. This enabled the President to appoint medical officers at ports and elsewhere for the purpose of giving medical treatment to disabled merchant seamen. The funds were obtained by a tax on those employed on American vessels.

The first marine hospital under the Act was at Norfolk, Va., in 1800. In 1802 a marine hospital was built for the port of Boston, and from time to time hospitals were built at other important seaports. To provide for the relief of seamen on inland waters Congress passed in 1837 an Act for the appointment of a board of advisory medical officers of the Army. A number of hospitals were established on its advice.

The evolution of public health functions from this service was along natural lines. The medical officers, in providing care for the American merchant marine, were often the first physicians to diagnose such diseases as Cholera, Yellow Fever, Small-pox and the like, which were being imported into the United States. In the epidemics of Cholera which occurred in certain ports of the United States the marine hospitals and their medical officers were utilized for the relief of those suffering from the disease. During the Civil War the marine hospitals, together with the medical officers, were used by the military authorities, both North and South, for the care of the military forces.

Not until 1878 did Congress authorize any extensive use of the Marine Hospital Service as a Federal Health Service. An Act of 1878 gave broad powers to the Service to co-operate with State and local health authorities in the control of disease, especially of Yellow Fever. In 1890 Congress decided to utilize the Marine Hospital Service as the Federal Health agency for the prevention of inter-State spread of Cholera, Yellow Fever, Small-pox and Plague. In 1893 the powers of the Marine Hospital Service in this regard were extended to cover all infectious and contagious diseases, in co-operation with State and local health agencies.

The efficiency of the Marine Hospital Corps in the control of epidemic diseases became widely recognized. In 1889 Congress passed an Act which made possible the further organization of the Marine Hospital Corps, and provided that the officers be commissioned in grades similar to those of the medical department of the United States Army. An Act of 1875 had already provided that the Surgeon-General (supervising surgeon) should be appointed by the President, with the consent of the Senate.

In 1893 the Marine Hospital Service was organized into the Federal Health Service. Congress continued to impose additional health functions upon the Service, and in 1902 changed its name to the ‘Public Health and Marine Hospital Service’ and made it a health service in name as well as function. The larger part of its duties, up to this time, had been the combating of epidemics, especially those of Yellow Fever, which from time to time swept the country. With the threat of Bubonic Plague in 1900 at San Francisco, the Marine Hospital Service was placed in charge of control methods and succeeded in preventing any extensive spread of the disease.

In addition to the quarantine and hospital functions, the activities of the Service soon came to include research and educational work. In 1902 Congress authorized the establishment of the Hygienic Laboratory for investigating Cholera, Yellow Fever, and other conditions. The Laboratory grew rapidly and is now a very important research institution, equipped for carrying on pathological, zoological, pharmacological, bacteriological, chemical, and physiological work.

From the control of epidemics, the Public Health and Marine Hospital Service began to develop control measures for the more common contagious and infectious diseases, such as Typhoid Fever, Diphtheria, and Scarlet Fever. The history of the wonderful control of Typhoid Fever which has taken place in the United States within the past twenty years is a part of the history of the Public Health Service in co-operation with State and local health agencies. Typhoid fever, which formerly took a toll of more than 50,000 lives annually, is responsible for the death of a mere fraction of this number at the present day.

The development of health functions of the Public Health and Marine Hospital Service continued until Congress in 1912 changed the name to its present one, the ‘United States Public Health Service’, and at the same time gave it broad powers to investigate the diseases of man and the pollution of navigable streams and lakes.

During the courses of Federal development the separate States of the Union were not devoid of protagonists of State intervention in matters of public health. Among these was Lemuel Shattuck (1793-1859), who, like Chadwick, was no medical man, but a student of social problems. Under the influence of Chadwick he drafted in 1850 the _Report of the Massachusetts Sanitary Commission_. This publication set forth a complete scheme of Public Health organization. The formation of the first State Board of Health in Massachusetts was, however, delayed till 1869. In this matter Massachusetts was, in fact, anticipated by Louisiana, which obtained a State Board of Health in 1855, and by New York City, which obtained a Board of Health in 1866. Most of the States followed in the seventies. The seventies and eighties were the decades in which the general principles suggested by the work of Pasteur and Koch were put into effect. The working hypothesis of sanitarians of the time was that filth and ill-drainage were direct factors in the production of epidemic disease. The view is now untenable, but there was unquestionably an immense improvement in health conditions resulting both directly and indirectly from the improved drainage, water-supply, housing, and the like that the agitation had stimulated.

As the bacteriological discoveries of the time became generally accepted, they were widely applied on American soil to the administrative control of disease, notably by the New York Department of Health under Hermann M. Biggs. That body, in 1892, instituted a bacteriological laboratory, the scope of which has steadily increased. Its work in connection with Diphtheria is elsewhere discussed (pp. 265-6).

To follow into our own time the development of factory legislation, vital statistics, school medical service, local health authorities, municipal laboratories and clinics, methods of food inspection, would be to write a text-book of Public Health Administration. In all these developments we see working the rational spirit in the peculiarly English field of Preventive Medicine. The spirit of Rational Medicine cannot function, however, without material upon which to work. The basis, the elementary matter, as it were, of that material, is the conception we form of the nature of the bodily processes. Such a conception it is the function of Physiology to provide and to Physiology we therefore now turn.

A ‘Seamen’s Hospital Society’ was founded in England in 1817. Its first hospital was the _Grampus_, an old 50 gun ship moored off Greenwich. This was succeeded in 1830 by the _Dreadnought_, 104 guns, and this in 1857 by the _Caledonia_, 120 guns, renamed _Dreadnought_. In 1870 this last wooden _Dreadnought_ was broken up and the patients were transferred to a building on shore close by. The darkness, damp, ill-ventilation, noisiness and septic character of a wooden ship made it thoroughly unsuitable for hospital purposes.

In 1899 the ‘Seamen’s Hospital Society’ established a special Hospital and School for Tropical Diseases such as are peculiarly common among seamen. ]

§ 3. _The Transition to a Physiological Synthesis._

Modern developments in physiological knowledge introduce an important period in the History of Medicine, for the study of the functions of the body is a natural portal of entry to the study of the perversions and suspensions of those functions that we call disease. The general character of physiological thought during the modern period may perhaps be described as the ‘synthetic study of the animal body’. The study has become synthetic because organs have not been studied so much in and for themselves as in relation to other organs. There has been, in fact, during the period, an increasing consciousness of the integration of the organs into one organic whole, the entire process being under the control of the nervous system, the various parts of which are themselves integrated (p. 308). This movement has, to some extent, mitigated the ever growing evils of scientific specialization.

(a) _Anatomy and Embryology in the Earlier Nineteenth Century._

Let us first glance at the state of anatomical knowledge in the early and middle nineteenth century. The general structure of the animal body was well known. Descriptive Anatomy was not far from where it now is. Comparative Anatomy, which had made good progress, was given a fresh impetus by the researches and by the authority of a brilliant group of French investigators, headed by Baron Georges Cuvier (1769-1832), whose influence spread to England, Germany, and America, where the leading exponents were Richard Owen (1804-92), Karl Gegenbaur (1826-1903), and E. D. Cope (1840-97). Cuvier was a biological dictator whose opinion did much to encourage investigation, and something to discourage some important investigators. His services to Comparative Anatomy can hardly be overrated. There was, however, still no effective knowledge of the anatomical differences between the races of man, while the species of man and of allied forms, whose skeletons palaeontologists have since described, were quite unknown.

As regards knowledge of the process of Development of the animal body, the broad lines of Embryology were being put on a firm basis by Karl Ernst von Baer (1792-1876), whose work was finished in 1837, though he lived another forty years. The subject was to be given a new meaning by the evolutionary school, which applied to new details and to particular instances the work of Charles Darwin (1809-82). Foremost of this school was Francis Maitland Balfour (1851-82).

(b) _Chemical Physiology in the Earlier Nineteenth Century._

The analysis of the functions and workings of the body had advanced far less than the knowledge of its structure. The study of Respiration was perhaps in the best position. The elementary conception of Respiration attained by Lavoisier at the end of the eighteenth century (p. 155) was hardly extended till E. F. W. Pflüger of Bonn (1829-1910), in the sixties and seventies of the nineteenth century, showed that the essential chemical changes of respiration do not occur in the blood or in the lungs, but in the tissues.

A very important figure in the scientific world of the thirties and forties of the nineteenth century was the German Justus von Liebig (1803-73), professor of Chemistry at Giessen. He was a convinced mechanist, and over the door of the University Laboratory which he founded he had inscribed the dictum _God has ordered all His Creation by Weight and Measure_. His great achievement was his application of chemical knowledge to physiology. He did much to introduce laboratory teaching, and certain apparatus which he invented is still in constant use.

Liebig greatly improved the methods of organic analysis and notably he introduced a method for determining the amount of urea in a solution. This substance is found in human blood and urine, and was the first organic compound to be ‘synthetized’, that is to say, built up from inorganic materials. It is of very great physiological importance. This is due to the fact that it is regularly formed in the body in the process of breaking down the characteristic nitrogenous substances known as proteins. Along with his colleague, Friedrich Wöhler (1800-82), who had already synthetized urea, Liebig wrote a famous paper (1832) in which he showed, for the first time, that a complex organic group of atoms--or ‘radicle’ as it is called--is capable of forming an unchanging constituent through a long series of compounds, behaving throughout as though it were an element. This discovery is of primary importance for our conceptions of the chemical changes in the living body.

From 1838 onwards, Liebig devoted himself to attempting a chemical elucidation of living processes. In the course of his investigations he did pioneer work along many lines that have since become well recognized. He taught the true doctrine, then little recognized, that animal heat is the result of combustion, and is not ‘innate’ (compare p. 156). He classified articles of food with reference to the functions that he conceived they fulfilled in the animal economy. An outcome of this was his food for infants and his extract of meat. Very important was his teaching that plants derive the constituents of their food, their carbon and nitrogen, from the carbon dioxide and ammonia in the atmosphere, and that these compounds are returned by the plants to the atmosphere in the process of putrefaction. This discovery made possible a philosophical conception of a sort of ‘circulation’ in Nature. That which is broken down is constantly built up, to be later broken down again. Thus the wheel of Life goes on, the motor power being energy from without, derived ultimately from the heat of the sun.

It was very unfortunate that Liebig conceived and adhered to a totally wrong view of the nature of putrefaction and fermentation, which it took Pasteur long years to displace.

(c) _Nervous Physiology in the Earlier Nineteenth Century._

From Chemical Physiology we turn to glance at the knowledge of the Nervous System. Charles Bell and his contemporaries (p. 145) had attained to a clear distinction of the nature of motor and sensory nerves and their separate origin from the two spinal roots (Fig. 98). The next fundamental contribution was made by Marshall Hall (1790-1857), who established the difference between volitional action and unconscious reflex (1833).

The fundamental ideas in the conception of reflex action had already been adumbrated by Descartes. In the view of that philosopher, any stimulus is transmitted along nerve-fibers to the central nervous system. There, on account of existing nervous connections, it gives rise to a fresh impulse which passes along outgoing nerve-fibers to the active organ, muscle, or gland, which is thereby excited to activity (p. 128). Thus, every action of the organism, and its life as a whole, conforms to definite laws. These laws must be directed to its preservation, or organisms would cease to exist. It is thus possible to look on organisms simply as elaborate mechanisms. Except that we know that we ourselves think and feel, we might eliminate mind from our consideration of the action of beings other than ourselves. Such was the view taken by the mechanists and other members of the iatro-physical school (pp. 127-131), which followed, to a greater or less extent, the teaching of Descartes. The course of physiological advance may be described, briefly, as the expulsion of the mental element from process after process associated with vital activity. This avenue leads on to a philosophical discussion whither we shall not now follow. It will suffice, at the moment, to remind the reader that only through the channel of _his own_ thinking and feeling is he able to follow these physiological discussions at all.

The conceptions of Descartes and of his successors were greatly extended by Marshall Hall. Interest was lent to Hall’s work by the contemporary discovery by French observers of what was regarded as a special center governing respiration--a very important reflex--in the lower part of the brain. Hall’s work gave ‘reflex action’ a permanent place in Physiology.

An afferent impression from a sense organ to the spinal cord may give rise to an efferent impulse by a purely intra-spinal process. This impulse may be of the nature of a complex and balanced muscular act involving a whole system of muscles, some of which may be antagonistic to each other. All this may take place not only unconsciously, without any intervention from the higher nerve-centers in the brain, but even in an animal from which the brain has been removed. On the other hand, channels exist (and are indicated in the diagram) for passage of impressions to and impulses from higher centers. These higher centers in many cases control or modify the resulting muscular or other action to a greater or less degree.

]

Since Hall’s time there has been a great extension of the conception of reflexes. It has been shown that, besides the simple nervous arc (Fig. 99), there are more complex nervous arcs which depend for their action on the integrity of an elaborate mechanism. The nervous system is ‘integrated’ under higher and higher centers, till at last the highest centers of the brain are reached (pp. 308-11). Many of the ordinary acts of life, sneezing, coughing, standing, walking, even breathing, are expressible as reflexes. The attempt has also been made to press the ‘instincts’ into the same category. But it is difficult to separate the instinctive from the volitional elements or to define either. Vast, therefore, as is the development of this department of physiology, it is a very delicate task for the historian to pass any verdict upon it. The ultimate value of all this work must depend upon the conception that the next generation attaches to the mental element in vital phenomena. There is evidence of reaction at the present time from the extreme mechanist physiological position.

Lastly, in the discussion of work on the nervous system comes the question of the localization of functions of the brain. The possibility of such localization is a very ancient speculation. The idea was developed along rational lines, in the first third of the nineteenth century, by certain Viennese workers who, having made important contributions to science, unfortunately afterwards degenerated into phrenological quacks. Later several German observers began the study of the electrical excitation of those parts of the cortex of the brain which specially control movement (Fig. 100). The work was continued and developed by a number of distinguished French and English observers, among whom Paul Broca (1824-80), Hughlings Jackson (1834-1911), and Sir David Ferrier (1843-) should be commemorated. Under their influence many operations usually regarded as involving complex mental processes, such as vision, speech, reading, writing, drawing, have been represented as depending on simple nervous relationships. Centers for the initiation of these operations have been described. Of late years, there has been reaction from this mechanical conception of the brain as an organ of the mind. The older school has, however, achieved clinical success especially at the hands of the great French physician Jean Marie Charcot (1825-93) and his pupils.

§ 4. _The Experimental Foundations of Modern Medicine._

We may turn back to consider those who have been the immediate progenitors of modern Physiology. Among these, three men stand out beyond all others. In order of seniority, and perhaps of genius, they are Johannes Müller, Claude Bernard, and Karl Ludwig.

(a) _The Work of Johannes Müller._

Johannes Müller (1801-58) was the greatest physiologist Germany has produced, and perhaps the greatest physiologist of all time. His genius was of the universal type and, despite his early death, he attained equal distinction in every department which he touched. Among these were Comparative Anatomy, Embryology, Physiological Chemistry, Psychology and Pathology. He was a careful scholar, well versed in the history of the subjects which he taught, and as great a teacher as he was an investigator. A very large number of the best-known men who have advanced Medicine during the nineteenth century were his pupils while he was a professor at Berlin. His lovable character was pervaded by a mystical tendency.

Müller’s text-book of Physiology began to appear in 1834. It introduced into the subject the comparative and psychological points of view, which were not fully appreciated until the generation that followed. The most remarkable generalization associated with his name--and one further developed by Ewald Hering (1834-1918)--is the ‘Law of Specific Energies’. According to this law each sensory nerve, however stimulated, gives rise to its own specific sensation and to no other. Conversely, the same stimulus applied to different organs of sense produces a different sensation in each organ--that sensation, in fact, that is its specific attribute. Thus electrical, mechanical, thermal stimulation produce only the sensation of light when applied to the optic nerve. On the other hand, any particular form of stimulation, for example electrical, produces sensations of light, smell, hearing or taste if applied to the appropriate nerves.

A moment’s reflection will enable the reader to realize the very great philosophical importance of these conclusions. They provide experimental evidence that the things of the external world are not in themselves discernible by us. Such external things we know only by the events to which they give rise acting on our senses, and yet from one and the same event utterly different sensations arise within us. To beings with senses different from ours the world also would be different. The ‘Law of Specific Energies’ is thus fundamental for our view as to the range of validity of Scientific Method.

Among other important contributions of Johannes Müller to the physiology of the nervous system were his experimental confirmation of Bell’s researches on the spinal roots (p. 145) and his experiments on the production of the voice. He launched important theories in explanation of color vision, of the mechanism of hearing, and of the phenomena of fever. He was one of the first to use the microscope in pathology and he was one of the founders of Physiological Chemistry.

Like every investigator Müller made mistakes. In 1840 he stated that the velocity of a nervous impulse could never be measured. By 1852 his gifted pupil, Hermann von Helmholtz (1821-94), had measured it. Much of Helmholtz’s work hardly comes within our department. He was, however, inventor of the instrument known as the _Ophthalmoscope_, by means of which the interior of the eye can be examined. This is the main factor which has enabled Ophthalmology to develop along true scientific lines (p. 319).

(b) _The Work of Claude Bernard._

Claude Bernard (1813-78), the great French physiologist, was Müller’s junior by twelve years and was in almost every respect a contrast to him. His mind was of that peculiarly French type to which anything mystical is abhorrent. He had few eminent pupils who owed much to him directly, but the influence of his ideas, through his writings, can hardly be exaggerated. Especially Bernard was the founder of ‘Experimental Medicine’, that is of the artificial production of disease by chemical and physical means. This is one of the most important scientific movements within our field.

Bernard’s great discovery, which occupied him for over ten years, was that the liver has the power of building up and storing certain highly complex substances, derived from the food and brought to it by the blood. The substances thus stored, and notably that known as _glycogen_, are distributed to the body according to its needs, in simplified and modified form. Now Wöhler in 1828 had synthetized urea (p. 206) and it was well recognized that this substance is a final degradation product which the body manufactures by breaking down the substances derived from food. It was also recognized that from this breaking-down process the bodily energy is obtained. Bernard showed that the body could build up complex chemical substances as well as break them down. This destroyed the conception, then still dominant, that the body could be regarded as a bundle of organs, each with its appropriate and separate functions. Bernard thus introduced what we may call a ‘Physiological Synthesis’, a conception of great import for the development of medical ideas.

No less important, and bearing on the synthetic view of the working of the animal body, was Bernard’s work on the physiology of digestion. Up to the time of Bernard, an elementary knowledge of the facts of digestion in the stomach constituted the whole of digestive physiology. While Bernard was working on the glycogenic function of the liver, another worker had suggested that the secretion of the organ known as the ‘pancreas’, or sweetbread, emulsifies fats. Soon after, a German researcher showed that pancreatic juice acts on starch. Bernard now stepped in and cleared up the whole subject. He showed that digestion in the stomach is, as he described it, ‘only a preparatory act’. He proceeded to demonstrate that the pancreatic juice, passing into the intestine, emulsifies the fatty food substances there and splits them up into fatty acids and glycerin. He further demonstrated the power of the pancreatic juice to convert starch into sugar, and he showed that it has a solvent action on such ‘proteids’ or organic nitrogenous substances as have not been dissolved in the stomach.

The third great achievement of Bernard was his exposition of how the blood-supply to the different parts of the body is regulated. This we now call the ‘Vaso-Motor Mechanism’. In 1840 the existence of muscle fibers in the coats of the smaller arteries was discovered. Bernard showed that the contraction and expansion of the ‘arterioles’ is associated with a complex nervous apparatus. The reactions of this apparatus depend upon a variety of circumstances in a variety of other organs; again an illustration of the close and complex interdependence of the various functions of the body upon each other.

(c) _The Work of Karl Ludwig._

Karl Ludwig (1816-95) held a series of professorships at Marburg, Zürich, Vienna and Leipzig. He was, after Müller, the greatest of German physiological teachers, and he surpassed even Müller in the number of his pupils. As a physiologist he was chiefly remarkable for his ingenuity as an inventor, for his wide and deep knowledge of the physical sciences and for his extreme generosity in handing over his work to his pupils.

Among the many lines of investigation of fundamental importance which Ludwig initiated, some of the most remarkable depended on the discovery of new methods. Just as the microscope had opened to the anatomist unexplored fields of research by bringing him into closer relation with objects which were hitherto beyond his scrutiny, so the rapid progress of physics and chemistry had placed more exact modes of observation and of measurement within reach of the physiologist. But the application of these methods was attended with great difficulty; there was no physiological laboratories, no instruments, no capable mechanicians to whom the physiologist could apply for assistance. Under such conditions, ingenuity and resource were indispensable to success, and in these qualities Ludwig was pre-eminent.

Accordingly, we find that two of the most important of the early investigations of Ludwig were as much due to his ingenuity as an inventor as to his clear grasp of the physiological questions which his inventions were intended to elucidate. The most interesting of these inventions, or rather adaptations, is the mechanically rotating drum or _kymograph_, as it is called. The word itself is derived from two Greek words which mean ‘wave writer’. This instrument is now widely used, not only in Physiology but in every department of Science in which permanent records of any continuous movement are desired. The most familiar instance is the self-recording barometer. The kymograph--the use of which had been suggested by Thomas Young (p. 319, and Fig. 101) in 1807--led to much wider applications of the method of automatic record. Ludwig himself applied it to indicate the movements of respiration, as well as the variations in arterial pressure. Subsequently it became further adapted to the ‘graphic method’, and it serves not only for the investigation of animal movements of every conceivable kind, but even for the transient and delicate electrical changes which are associated with vital action.

An instrument invented by Ludwig is the mercurial blood-pump, the purpose of which is to separate from a known quantity of blood, derived directly from the circulation, the mixture of gases which it yields to a vacuum. This is an indispensable apparatus for the investigation of the physiology of breathing.

Ludwig devoted much attention to the physiology of secretion. Here his work has been of great importance in connection with the time-honored discussion between the ‘vitalists’ and the ‘mechanists’. He succeeded in showing that the process of secretion can be so transformed experimentally as to do external mechanical work. This was victory for the mechanist theory. The idea has since been applied to many structures.

It is impossible to attempt here any general summary of the conclusions reached by physiological research since Ludwig. Some have affected the actual practice of Medicine. Others are too recent or too little certain to have reacted in this manner. It is, however, safe to say that the more important conclusions of the three modern founders of the science, Müller, Bernard, and Ludwig, form the main scientific background of the clinical practice of our time. The results of the movement that they represent, together with the knowledge of the cellular structure of the body (§ 5, p. 219) and of the life-histories of the disease-causing organisms (§ 6, p. 224), are the three main groups of ideas which separate the physician of our day from Laënnec (p. 161).

The cylinder H turns with the axis AB on which it is rigidly fixed. It is rotated by a handle at A which raises the weight C. When the weight is allowed to fall the cylinder rotates automatically. The rest of the apparatus is devised to secure constancy in rate of rotation. This was done by utilizing the effects of centrifugal force.

(As the rate of rotation increases the pendula D and E fly apart, they separate the weights F and G. These move with friction which increases as they separate, thus decreasing the rate of rotation.)

The movements of the pen at K are transferred into permanent graphic form by writing on the rotating cylinder H.

]

§ 5. _The Cell Theory and Cellular Pathology._

During the process of the microscopic analysis of plants that took place in the seventeenth century a number of observers distinguished the walls of plant-cells and the word _cell_ was introduced into the English language. Less clearly, a similar structure was discerned in animals. No real understanding of the nature of cells was, however, reached. Little farther progress was made in the eighteenth century, but just at its close a young French microscopist, Marie François Xavier Bichat (1771-1802), likened the microscopic structure of the animal body to the substance of a woven fabric. The word he used was the old French term _tissu_. He perceived that the different parts of the body, bones, muscles, nerves, blood-vessels, and the like, each presented a characteristic microscopic pattern. According to these appearances he analyzed the parts of the body into twenty-one ‘tissues’. Study of this kind came to be called ‘Histology’ (Greek _histos_ = web).

During the seventeenth, eighteenth, and early nineteenth centuries, some advances were made in the knowledge of those organisms whose bodies are made up of only one cell, but their essential nature was still unappreciated. In the early nineteenth century a number of botanists and others were observing cells and cell contents. But no important advance in the interpretation of the appearances was made until the matter was taken up by Schleiden.

Matthias Jakob Schleiden (1804-81), professor at Jena in 1838, put the matter in a new light. He noted, as had certain of his predecessors, the constant presence in every cell of the structure we now call the ‘nucleus’, and came to the conclusion that it is essential to the life of every cell. He reached the conception, moreover, that in a multi-cellular organism, such as a tree, every cell has a double life, one an essential and independent one, pertaining to its own development alone, the other an incidental and dependent one, in so far as it is an integral part of the plant. His work was somewhat vitiated by a fanciful conception of the origin of new cells.

The work of Schleiden was amplified and corrected in 1839 by Theodor Schwann (1810-82), a pupil of Müller. He showed that the tissues of animals, like those of plants, are susceptible of analysis into cells, and the difficulty of this process arises from the extreme modification of such cells as have developed for various special purposes. He showed too that the ovum or egg of animals is, in the first instance, a single cell, and that the cells of the body are derived and descended from it. He demonstrated that the entire animal or plant body is composed either of cells or of substances that are excreted or thrown off by cells. He gained some insight into the life of animal cells and in doing so he invented the very useful word _metabolic_. The word means ‘liable to change’. It was used by Schwann, and is still habitually used in modern Medicine to indicate chemical changes within the body which are specially associated with living activity.

Contributions to the cell theory were made by other botanists. Hugo von Mohl of Tübingen (1805-72) distinguished the contents of the vegetable cell just under the cell-wall from the watery sap that fills the interior, introducing for it the term _protoplasm_ (1846). The Swiss, Karl v. Nägeli (1817-91), by chemical examination proved that protoplasm is nitrogenous and differs from other cell constituents (1862).

The cell theory was placed on a firm and clear footing by Max Schultze (1825-74), successor of Helmholtz (p. 213) as professor of Anatomy at Bonn. He defined the cell as ‘a lump of nucleated protoplasm’ (1861), introduced the idea of protoplasm as ‘the physical basis of life’, and showed that it presented essential similarities, physiological and structural, whether in plants or animals, and whether in higher or lower forms.

The study of tissues, Histology, was raised to the status of an independent science by the Swiss, Albrecht von Kölliker (1817-1905), pupil of Müller and professor at Würzburg, who wrote the first text-book on the subject (1850-52). Apart from this achievement, Kölliker is remarkable for having reached some of the conclusions in connection with heredity that are associated with the name of Mendel, of whose work he knew nothing.

Even more influential on medical thought than Kölliker was Rudolf Virchow (1821-1902) of Berlin, one of the leading names in modern Medicine. There is indeed hardly any department of medical thought that has not gained something from Virchow’s work. His great achievement is the way in which he carried the Cell Theory into the analysis of diseased tissues. In his _Cellular Pathology_ (1858) he analyzes diseased tissues from the point of view of cell formation and cell structure. Important sections of the science of Cellular Pathology have been explored so well by Virchow that they have been little extended by his successors. He initiated the familiar idea that the body may be regarded as ‘a cell State in which every cell is a citizen’. Disease is often but a civil war. The white blood corpuscles, which have the power of engulfing and rendering innocuous bacteria and other foreign bodies, have been compared to police or scavengers. In some respects Virchow was strangely conservative, and notably he opposed the evolutionary view of the origin of living forms. Virchow’s conceptions of the functions of the white blood corpuscles were largely extended by the Russian biologist Élie Metschnikoff (1845-1916) and the English worker Almroth Wright (1861-).

Since Virchow and Kölliker the study of the intimate structure and workings of the cells themselves, as distinct from the tissues, has become a separate and independent science under the name of _Cytology_. It may even be extended to the study of cells in disease as _Cyto-Pathology_.

Among the major developments of Cellular Pathology and Cyto-Pathology is the study of abnormal ‘new growths’. The most malignant types of these belong to the group known as the ‘Cancers’. The occurrence of most of these becomes more frequent as life advances (Fig. 135). Their cytological features are now well known. A cancer consists essentially of an increase of cellular tissue, following abnormally rapid multiplication of one type of cell. The new growth is equipped with a blood-supply which enables it to increase at the expense of other tissues and regardless of their needs.

Cancers almost always arise at one point, and are very seldom multiple in origin. It is fairly established that they are not infectious or contagious, and there is no very satisfactory evidence that a tendency to them is inherited. Our scientific knowledge of Cancers is largely derived from animals. Cancers are ‘specific’ in the sense that those of one animal species will not grow when inoculated into another species. An immense amount of work has been done on inoculated Cancers, but it has become evident that some physiological factor is involved in Cancer incidence such that an inoculated Cancer is not entirely comparable with so-called ‘spontaneous’ Cancer. As to what that physiological factor can be we are still in the dark.

Although we know nothing effective as to this physiological factor, yet experiments in the artificial production of Cancer, apart from inoculation, have been attended with success. That various forms of chronic irritation are associated with the onset of Cancer has long been clinically recognized. It has been found possible to reproduce experimentally this relation between irritation and new growth, and so, for example, to induce Tar Cancer in mice. Nevertheless, it must be admitted that Cancer investigation is in an unsatisfactory state, and has yielded fewer positive results than any other department of Pathology of comparable importance. It is possible that we do not yet know enough of normal Cell Physiology to investigate with profit the forms of cellular perversion known as Cancer.

Drawings by Theodor Schwann to illustrate the nature and origin of animal cells. All are highly magnified.

FIG. 102. The first step in the origin of cartilage from cellular tissues. At the lower part the young cells are without cell-walls. In the upper part they have formed walls and are beginning to secrete cartilaginous substance. Nuclei and nucleoli are clearly visible.

Above is shown a piece of maturer cartilage, in which the cells are imbedded in a mass of cartilaginous material.

FIG. 103. Pigment cells, such as are characteristic of the skin of the frog. In the lowest cell, which is contracted, the nucleus is concealed by the pigment. The upper two are more expanded and in them nuclei can be seen.

FIGS. 104 & 105 show how structures of very diverse form can be differentiated from cells of the same type.

FIG. 104. Young cells from a developing feather. These cells may enlarge, secrete hard walls, and form the fine spongy tissue of the inner part of the shaft of the feather. Or the cells may elongate, the protoplasm become granular, and finally break up into fibers (Fig. 105). These form the tough fibrous matter of the outer part of the shaft of the feather. In either case, the nucleus disappears and the cell dies.

]

§ 6. _Establishment of the Doctrine of the Germ Origin of Disease._

The view that many diseases, especially those of a contagious or infectious nature, originate from the invasion of the body by special organisms and their multiplication within the body, came into prominence in the second half of the nineteenth century. There had been many previous adumbrations of this view and, in its final establishment, more than one hand may be discerned. Above all others who have worked in this field towers the mighty figure of Louis Pasteur (1822-95). We shall do no grave injustice to any man if we treat the scientific demonstration of the doctrine as the product of his superb genius.

The opening of Pasteur’s interest in disease can be seen in his work on fermentation. At first he was faced with the opposition of Liebig. According to that eminent chemist, fermentation was not the result of vital activity but was a purely chemical change (p. 207). A ferment he regarded as an unstable organic product, the character of which determined the manner of decomposition of the medium in which it is placed. Pasteur demonstrated that, as there is a specific alcoholic ferment, so there is a specific milk-souring ferment. Any nitrogenous matter present in a fluid containing it will serve as food for the development of a ferment, but will not of itself induce fermentation. Ferments have, he demonstrated, the power of reproduction. Pasteur rapidly seized on the idea of the specificity of ferments. An albuminous sugar solution can be converted into various products by the addition of various ferments. According as one sows, so will one reap. The milk-souring ferment, Pasteur concluded, is organized and living, and its action is correlated to its development and organization. No life, no ferment; no ferment, no fermentation.

1. Bacillus of Turned Wine. 2. Ferment of Soured Milk. 3. Butyric Ferment. 4. Ferment of Ropy Wine. 5. Ferment of Vinegar. 6. Amorphous deposit. 7. Sarcinae.

]

During the next years Pasteur applied himself to a study of ferments and notably of those which involve deterioration of wines and beers. This led him to perceive that there is a great multiplicity and variety of these organisms. Now it was an old and well-known view that fermentation, putrefaction, and the infection of disease had much in common. It was perfectly natural, therefore, for Pasteur to regard the latter in the light of a vital process. A great difficulty was, however, the demand that any such doctrine made on the germ-bearing capacity of the air. Cities were not slow to avail themselves of this weakness, and pointed out that, according to Pasteur, the air must be one solid mass of germs! For the opponents of Pasteur the living organisms found in the process of fermentation or decomposition were the result, not the cause, of the process. These organisms were regarded by them as spontaneously generated in the fermentation process. Thus arose a discussion of the old theme of spontaneous generation.

By 1859--the year of publication of Darwin’s _Origin of Species_--Pasteur was engaged in controversy as to the ‘Origin of Life’. The discussion specially turned round what were then regarded as the lowest forms of life, the Bacteria. Were they ever spontaneously generated, or were they not? If a flask of broth, supposedly sterilized by boiling, went ‘bad’ and organisms appeared in it, was it certain that they had come from without, or could they have been spontaneously generated by the broth itself? Life must begin somewhere. Then why not here at this lowest stage? If this view be justifiable, Pasteur’s doctrine of the nature of ferments must fall to the ground.