The system of medical specialization so characteristic of our age, though begun in England, spread to the Continent and affected no school more profoundly than that at Vienna. This seat of learning was long the main place of pilgrimage for English speaking medical men who desired to continue their studies abroad. The high development of specialism at Vienna, which began soon after the middle of the 19th century, reacted in its turn on the English schools. This specialism has tended to take on a peculiar form in England, owing to the fact that the pro fession of medicine there has remained almost entirely unen dowed. In England even the most scientific exponents of medi cine have, till quite recently, always been forced to make their livelihood in practice. In medicine the existence of a specialty has thus often depended not so much on the direction and extent in the acquisition of new knowledge, as on the increasing demand for a very high degree of technical manipulative skill.
Moreover, the medicine of the 19th century, in so far as it is more scientific, differs from that of the older period in that it is more clearly founded upon physiological investigation. Thus physiology has become the natural introduction to medical study, as has been recognized in the medical curriculum. Therefore, to render intelligible any discussion of the medical thought of the last century, it is necessary to examine the physiological develop ments which have influenced that thought most deeply.
By the beginning of the 19th century the knowledge of the naked eye structure of the human body had been pushed well nigh as far as possible. Subsequent progress, in so far as it has taken the direction of morphology, the pure study of form, has been in the departments, firstly, of comparative anatomy, in which the leading figure was that of Georges Cuvier (1769-1832) (q.v.) in France, followed by Richard Owen (1804-92) (q.v.) and Thomas Henry Huxley (1825-95) (q.v.) in England, by Karl Gegenbaur (1826-1903) (q.v.) in Germany, and by E. D. Cope (1840-97) in America; secondly, of development or embryology, a movement which was led by Karl Ernst von Baer (1792-1876) (q.v.) and Wilhelm His (1831-1904) in Germany, Francis Mait land Balfour (1851-82) (q.v.) in England, and C. S. Minot
(1852-1914) in America. The general character of the work of these men is considered under separate articles. (See COMPARA TIVE ANATOMY and EMBRYOLOGY.) Far more important in its effect on medicine than the morpho logical movement has been the great impulse given to physio logical progress by a series of very great teachers. Most of the more prominent of these in the earlier part of the modern period were Germans. France has taken a secondary place with the isolated but superb genius of Claude Bernard. The English-speak ing world did not come to occupy an important position in the history of modern physiology until the last quarter of the 19th century, though at an earlier period she produced Sir Charles Bell (1774-1842) (q.v.) and Marshall Hall (179o-1857). Since the latter part of the 19th century England has come to occupy the main field with Michael Foster (1836-1907), Gaskell (1849 1914), Sir Edward Albert Sharpey-Schafer (1850-1935), Sir Frederick Gowland Hopkins (1861- ), Sherrington ), Bayliss (1863-1924) and Starling (1866-1927).
Muller, Liebig, Ludwig and Bernard.—The foundations of German physiology were laid by Johannes Miiller (1801-58) (q.v.), Justus von Liebig (1803-73) (q.v.) and Karl Ludwig (1816-95) (q.v.). These three men may be regarded as typifying the application of the comparative, the chemical and the physical methods to physiological investigation. They were all great teach ers, and the course of modern physiology as a separate science and discipline has been their work through their numerous pupils.
Claude Bernard (1813-78) (q.v.), perhaps more brilliant than any of them, has exerted his influence rather through his writings than personally.
text-book of physiology, which began to appear in 1834, marks the starting-point of physiology as a normal intro duction to medicine. Not only did Miiller's work sum up all the knowledge of the day, but it brought before the reader many new points of view. Foremost of these was the "Law of Specific Nerve Energies," according to which each sense nerve, however stim ulated, gives rise to the particular sensation that is associated with it and to no other, and conversely the same stimulus, applied to different sense organs, produces a sensation which accords with the organ stimulated. Thus, sensation is a specific attribute. This implies that the things of the external world are not, in them selves, discernible by us, but are known only by the way they act on the senses, acting in different ways on different senses. This conclusion is not only of physiological importance but is funda mental for our view of the validity of scientific method itself.