DEVELOPMENT OF MODERN MEDICINE 43 



of precision the diagnosis could be made with a definiteness, im- 

 possible by the use of the symptoms alone. 



The epoch-making work of Johannes Mueller in embryology and 

 physiology marked the beginning of modern physiology, and this, 

 with the unparalelled activity of Virchow in pathology, resulted 

 in an enormous development of scientific observation and product- 

 iveness. 



Corresponding activity marked the work in the sciences of chem- 

 istry, zoology, comparative and human anatomy, physics, botany, 

 and general biology. The development of the microscope gave 

 impetus to the study of the lower forms of life. In 1838, Ehren- 

 berg regarded infusoria as animals. In 1852, Perty claimed that 

 most infusoria should be assigned to the vegetable world. Cohn 

 proved the correctness of this conclusion and perfected a classi- 

 fication. In 1837, Bassi discovered the parasitic nature of silk-worm 

 disease. The parasitic form of favus and thrush was proved by 

 Schoenlein and Nagel respectively. Dovaine recognized the anthrax 

 bacillus in 1850. In 1857, Pasteur demonstrated that fermenta- 

 tion and putrefaction were caused by lower organisms and at the 

 same time forever set at rest the superstition of spontaneous gener- 

 ation. Obermayer recognized the spirillum of relapsing fever in 

 1873. Bacteriology became an exact science with the discovery by 

 Robert Koch of cultural methods which made the differentiation 

 of germs possible. 



The causative relations of bacteria and microorganisms to all 

 infective processes has been proved by the laws promulgated by 

 Koch. The discovery by Brieger, Panum and others of the poisons 

 produced by bacteria was another important step in the progress 

 of bacteriology as related to medicine. 



From the discovery and development of bacteriology, and especially 

 through the brilliant researches of Pasteur and Koch and of their 

 students, has resulted a knowledge which has revolutionized and 

 marked the birth of modern medicine. 



Parasites 



The discovery of the hematozoon of malaria by Laveran; the 

 recognition of the ameba of dysentery by Loesch ; of the ray fungi 

 and especially the actinomyces as infective agents in the lower 

 animals and in man and the more exact knowledge of other ani- 

 mal parasites infecting man and animals, which the microscope 

 has made clear, have been as epoch-making in parasitology as 

 the discoveries of Pasteur and Koch in bacteriology. 



The recognition of the relation of bacteria, protozoa, and ani- 

 mal parasites to infective disease has been the means of a more 



