6i6 THE POPULAR SCIENCE MONTHLY. 



INFECTIOUS DISEASES. CAUSATION AND 



IMMUNITY. * 



By GEORGE M. STERNBERG, M.D., 



SURGEON UNITED STATES ARMY. 



CERTAINLY, from a scientific point of view, no question in 

 medicine is more important than that which relates to the 

 causation of disease. An accurate knowledge of the specific etio- 

 logical agents concerned in the production of specific infectious 

 diseases forms the very basis of scientific medicine; and, as you 

 all know, researches which have been made during the past thirty 

 years have given us this accurate knowledge for a considerable 

 number of these diseases. I say thirty years, in order to include 

 the researches of Davaine upon anthrax ; but, as a matter of fact, 

 the principal portion of our knowledge relating to specific disease- 

 germs has been acquired during the past decade. 



As an introduction, a brief historical review of the progress of 

 our knowledge will perhaps not be out of place. But first I must 

 call your attention to the fact that this progress has been made 

 possible by certain improvements in methods of research, and es- 

 pecially by the following : first, the use of a cotton filter to ex- 

 clude atmospheric organisms from our culture media (Schroder 

 and Von Dusch, 1854) ; second, the sterilization of culture media 

 by heat (methods perfected by Pasteur, Koch, and others) ; third, 

 the use of aniline dyes as staining agents (first recommended by 

 Weigert in 1877) ; fourth, the introduction of solid culture media, 

 and the " plate method " for obtaining pure cultures (by Koch in 

 1881) ; fifth, the perfection of methods for cultivating anaerobic 

 bacteria. I have already referred to the researches of Davaine re- 

 lating to the disease of cattle and sheep known as anthrax. Hav- 

 ing ascertained that the blood of an infected animal constantly 

 contained a rod-shaped micro-organism, and that the smallest 

 quantity of this blood inoculated into a susceptible animal gave 

 rise to the disease and caused its death, Davaine, in 1803, boldly 

 announced his belief that the bacillus was the specific etiological 

 agent in this disease. The experiments of Davaine were not, how- 

 ever, generally accepted as conclusive, because, in inoculating an 

 animal with blood containing the bacillus, the living micro-organ- 

 ism was associated with material from the body of the diseased 

 animal. This objection was subsequently removed by the experi- 

 ments of Pasteur, Koch, and many others with pure cultures of 

 the bacillus. These were shown to have the same pathogenic 

 effects as had been obtained in inoculation experiments with the 



* Address in Medicine, delivered at Yale University, June 28, 1892. 



