CHAPTER XV 

 THE PHENOMENA OF INFECTION 



IT may be of interest to go somewhat into detail con- 

 cerning our ideas of the phenomena of infection. In all 

 infections there are two principal factors one the infecting 

 virus and the other the body cell. In addition to these 

 there is the environment in which the struggle for supremacy 

 between the virus and the body cell takes place. This con- 

 sists of the unorganized fluids of the body, and is of great 

 weight in determining the result of the contest. In the first 

 place, what do we know of the infecting virus? As we 

 have seen, bacteria are particulate, specific proteins. Since 

 they are particulate, we speak of them as bacterial cells. 

 It is not, however, essential that an infecting virus be 

 particulate in the sense that it be possessed of substance 

 and form recognizable to our limited sense of sight even 

 when aided by the most perfect microscope. There are 

 many filterable viruses. Some pass through our finest 

 porcelain filters and cannot be deposited from the fluids in 

 which they exist even when kept for hours in the most 

 efficient centrifuge manufactured. Theoretically, there 

 is no reason why a virus may not exist in any degree of 

 lability of structure. The bacteria are particulate and 

 solid, which means that 'their structure is so radically 

 different physically from the medium in which they exist 

 that they can be recognized by our sight, aided by proper 

 magnifying lenses, but viruses may be semi- or wholly 

 fluid. In such instances their structure is not sufficiently 

 differentiated from the medium that we can recognize 

 them. According to our conception, a living protein does 



