DEVELOPMENT OF MODERN MEDICINE 47 



of bacterial cultures and in the bodies of infected animals. When 

 the antitoxin thus formed was injected into an animal, it had the 

 power to protect that animal against the particular bacterial infec- 

 tion, or, if given subsequent to the infection of the animal, to miti- 

 gate the severity of the disease or entirely to check it. 



Thus Koch and his students established the principle of serum 

 therapy. Upon this principle there has been developed and given 

 to the world the anti-diphtheritic serum of Behring and of Roux, 

 and also an immunizing serum for Asiatic cholera, tetanus, ery- 

 sipelas, plague, epidemic dysentery, streptococcus infection, and 

 other diseases. While the serum treatment has not proved successful 

 in all of the diseases in which it has been used, it has been so success- 

 ful in some diphtheria, for instance as firmly to establish the 

 principle of serum therapy. The study of prophylactic sera by Paul 

 Erlich led to our present knowledge of immunity. His side chain 

 theory has established a working basis which affords superb fields 

 of research in physiologic chemistry which have already yielded 

 rich returns. 



Bacteriology made possible the comprehension of perfect cleanli- 

 ness and enables the surgeon to invade every part of the body 

 without fear of infection and has saved thousands of lives which 

 twenty-five years ago would have perished miserably as the result 

 of disease at that time inoperable, or as the result of infection from 

 contact with the surgeon. By means of cleanliness and skill, in- 

 duced by a broader experience, the surgeon has been able to add to 

 our knowledge information of great value which could have been 

 obtained probably in no other way. He has been able to study dis- 

 ease in the living body and show the relation of a disease process 

 to infection. He has thus been able to clear away many of the 

 misconceptions of symptomatology and diagnosis, especially in dis- 

 ease of the abdominal organs. 



Bacteriology has stimulated laboratory clinical diagnosis. Bac- 

 terial reaction to sera and blood cultural tests are of the greatest 

 aid to diagnosis. Clinical research work has command of an arma- 

 mentarium consisting of a knowledge of pathologic anatomy, of 

 physiology, of bacteriology, of chemic physiology, and of physics, 

 which allows of a precision in diagnosis never before at the command 

 of the physician. 



The evolution of bacteriology has afforded a stimulus and aid in 

 the advancement of parasitology, physiology, physio-chemistry, 

 and of other fundamental sciences. This knowledge has been more 

 directly applied to practical medicine than ever before. 



Indeed modern medicine is now so comprehensive that the student 

 must be thoroughly conversant with chemistry, inorganic, organic, 

 and physical, with physiology, with general biology, with human 



