4 BACTERIOLOGY. 



the instruments and methods for studying germs at 

 that time were inadequate. 



In the next thirty to forty years many new 

 methods were introduced which marked a rapid 

 progress in the study of germs; for example, the 

 use of aniline, dyes for coloring germs so that they 

 could be seen better under the microscope, and solid 

 culture media on which germs could be cultivated 

 and different kinds separated and studied. The de- 

 velopment of these new methods was due chiefly to 

 the genius of Koch, who also laid down certain laws 

 or conditions which had to be fulfilled before any 

 germ could be said to be the cause of any specific 

 disease. With improved methods and appliances the 

 relationship of germs to specific diseases could be 

 proven experimentally, and the discovery of the 

 germs o>f many diseases followed with great rapidity. 

 Since 1879 the germs causing the following diseases 

 have been discovered : Diphtheria, Leprosy, Typhoid 

 Fever, Tuberculosis, Tetanus (Lockjaw), - Influenza, 

 Bubonic Plague, Cholera, Meningitis, Pneumonia, 

 Syphilis, Gonorrhea, and others. 



The study of the life history or biology of these 

 germs has led to our present knowledge of the 

 cause, the course, and ways of preventing most of 

 the infectious diseases, and has put into the hands 

 of physicians the means whereby the character of an 

 infectious disease may be detected. 



From this brief sketch it is easy to appreciate 

 that bacteriology is, comparatively speaking, a new 



