ESSAYS ON BACTERIOLOGY. 117 



latter statement is true, we liave in the detection of 

 the diphtheria bacillus a positive means of recogniz- 

 ing or diagnosing diphtheria, and we at once begin to 

 see how the science of bacteriology becomes a part of 

 everyday practical medicine. 



Bacteriology has entered into and become a work- 

 ing part of practical medicine in several ways. It 

 suggests and directs general preventive measures 

 against the infectious diseases. It suggests and 

 guides preventive and curative measures in individual 

 cases; and it is affording tis more accurate and more 

 rapid means of diagnosis in an increasing number of 

 diseases. It is therefore becoming of importance to 

 every practicing physician, and of interest to every in- 

 telligent person, to know something of the methods of 

 bacteriological work, especially of that part of it 

 which is applicable in the working laboratory — ^that 

 is, in the consulting room of the doctor. The more 

 this work is studied the more will it appear that it 

 follows in many respects the principles and methods 

 of ordinary agriculture. Keeping this fact in mind, 

 many otherwise strange things become clear and 

 simple. 



The cultivation of bacteria has, mainly through the 

 efforts of a few great men like Pasteur and Koch, be- 

 come a comparatively simple matter, now taught in 

 every well-equipped medical school. In the earlier 

 days it was customary to cultivate 'bacteria in fluids, 

 such as beef broth. But with this method it is diffi- 



