tioiis of life. Diseases thiii- repiesent a reaction of the sum of the ooll.s wlueli lomi the body aKninst haniitiil influences, tlie causes ol' liiseascs. Vircliow's chief work "Die t'ellularpatliologie" appeared in 1858. Cireatcr attei\tion was now paid not alone to pathological anatomy, l)ut to its sister sciences, patho- logical chemistry, ex|)eriinen(a! patliolofiy, and liac- teriologj'. Tlie chief representati\es of experimental pathologj' were : in France, Claude Bernard (lsl.'i-78), Charles Edouard Brinvn-Seqiiard (lSlS-!)5), ami Etienne Jules Marey (h. 18)50); in Germany, Ludwig Traube (1818-76), Rudolph Virchow, and Julius Cohnheim (lS;i9-Sl); in Vienna, Salomon Striker (d. 1898) and Pliilip Knoll (1841-1900). Experiments on animals are extensively made to-day in tliis field of investigation.
Bactenolmjy , Theory of Immunity, Serotherapy, Dis- infection. — The first to suspect that living beings in- vade the organism and exist in the lilood and pus was the learned Jesuit Athanasius Kirclier (1(171), although there is no doubt that the " little worms " observed by him were really blood-corpuscles. With the help of his improved microscope Leeuwenhoek discovered a number of liacteria. The idea that infectious diseases were causetl b}' a living contagion invading the body from without was first expresseil in 1762 b.v the Vienna physician Markus Antonius Pleneiz (d. 1786). Otto Frietlrich Midler, in 1786, was the first to doubt that the microscopical living bcini;s. fbcn ci.nipii-i'd under the name of infu.wri<i. really bfloimi.l di the animal kingdom. In 1838, Christian tiottfried Ehren- berg gave a description of the finer structure of the "infusoria", but it was Ferdinand Cohn, who in 1S54 first ascertained with certainty that bacteria belonged to the vegetable kingdom From the studies that were now made concerning the vital qualities of these infinitesimal living beings of the vegetalile kingdom, Louis Pasteur (1822-95) definitely settled the contro- versy about spontaneous generation (gcncratio wqui- voca), and proved the materialistic view to be without foundation. What Pleneiz hatl only suspected was now clearly formulated by Ilenle, who defined the con- ditions under which bacteria are to be regarded as direct causes of disease. The imtiring activity of Robert Koch (d. 1910) from about 1S7S succeeded in bringing bacteriology to such a state of develop- ment that it could be made of service to practical medicine. Apart from ascertaining the bacterial origin of cholera and tuberculosis, Koch's greatest achievements are the improvement of the microscope (Abb6, Zeis), the method of colouration and pure cultures.
Jenner's success with the lymph of cowpox, a weakened poison as a protection against a full poison, as well as the old experience that those who had once recovered from an infectious disease usually became immune from new infection, led savants to look for the cause of the phenomena. In 1880 Pasteur, on the basis of liis experiments concerning chicken cholera, looked for the cause in the exhaustion of the nutritive material necessary for the bacteria in the body (theory of exhaustion), while Chauveau believed in a residue of metabolic products which prevented a new settle- ment of bacteria or new infection (retention theory). The investigation of Metschnikoff, and in 1889 of Buchner, advanced the idea that blood-serum pos- sesses a certain hostility to bacteria. In 1890 Von Behring proved that the blootl-serum of animals which has been made immune against diphtheria, if in- jected intoanotheranimal, would make the latter also immune against ili[)litl)eria. That element in the serum hostile to bacteria he called antitoxin. The intro<luction of antitoxin into the therapeutics of diphtheria in 1S92 was so far the greatest practical suc- cess of bacteriolog>-. Efforts were naturally made to secure by similar methods protection against other in- fectious diseases, efforts only partly crowned with
siicceas (tetanus, plague, cholera, snake poison). 'Fol- lowing Jeimer's method of producing immunity by means of living, weakened causes of infection, Pasteur (18S5) found a protecti<in against lyssa, while llafT- kine made experiments in ISOf) to combat cholera with killed germ.s, and in 1S97 similar experinienls with the Iilague. From 1891 tiates Koch's experimentation with extracts of bacteria against tul)erculosis. By means of pre[)arations of pure bacteria-cultures, made according to Koch's method, it became possible to devise exact methods for destroying bacteria. In the field of the modern theory of disinfection, Koch also worked as a pioneer, not only in precisely defining the dilTerenc<' lietween prevention of development and the killing of bacteria, but also by subjecting physical and chemical disinfectants to new tests. The modern steam sterilizers are based upon the discovery of Koch that steam under the ordinary pressure of the atmosphere is sufficient to kill even resistant lasting forms. He pointed out the inefTectiveness of alcohol, glycerine, and other substances upon the spores of an- thrax, and the diminished effect of carbolic acid in an oily or alcoholic solution. Von Behring's experiments showed a diminution of power of some disinfectants in the presence of albumen, concerning which Kronig and Paul made a special study.
Physiology is indebted for its perfection to the prog- ress of minute anatomy (doctrine of tissues) to the improved means of investigation (microscope, chemi- cal and physical apparatus), but especially to the fact that experiments on animals (vivisection) were once more extensively made. The principal physiolo- gists of the past century were in France and Germany. Fran(^ois Magendie (1783-1855), opposing Bichat (vitalism), maintained that there is no uniform vital energy, and that the vital qualities of the different organs are to be explained upon a physical and chemi- cal basis and by means of experiments. His investi- gations in hsemodynamics and the functions of the nervous system (roots of the spinal column), in which he supplemented the work of Charles Bell (Law of Bell-Magendie) are very important. Marie Jean Pierre Flourens (1794-1867) is known by his studies in disturbances of co-ordination, nutrition of the bones, and localization of the centre of respiration in the metlulla oblongata, and Fran^-ois Achille Longet (1811-71) by his work on the functions of the anterior and posterior columns of the spinal cord, the innerva- tion of the larynx, the nerves of the brain, and the law of the contraction of the muscles. The most famous French physiologist, a pioneer in the field of physiolog- ical chemistry, is Claude Bernard (glycogenic func- tion of the liver, the consumption of glycogen through work of the muscles, the discovery of vascular nerves, the chemistry of the bile and the urine, theory of diabetes mellitus, assimiliation of sugar, atrophy of the pancreas, the power of the pancreatic juice to digest albumen, and the theory of animal heat). The physi- ology of the circulation was elaborated by Etienne Jules Marey (b. 1830; blood pressure, mechanism of the heart, and the invention of the sphygmograph). The relation of muscles and nerves to electricity was studied by Guillaume Benjamin Duchenne (1806-75), while Charles Edouard Brown-S6quard (1818-94), the founder of modern organo-therapeutics, investigated the reflex irritability of the spinal cord, the blood, respiration, and animal heat. In Cireat Britain were Marshall Hall (1780-1857; theory of reflex action), Wilham Bowman (1816-92; structure of the striated muscles, and theory of the secretion of urine), Alfred Henry Garrod (1846-79; sphygmography, physics of the nerves), Augustus Volney Waller (1816-70; dia- pedesis of the red corpuscles of the blood, studies on nerve-fibres and ganglia. Waller's degeneration) and William Prout (178.5-1869; discovery of free hydrochloric acid in the gastric juice).
The Bohemian Johann Evangelist Purkynje (1787-