CHAPTER VI 



^ 



ACTION ON ANIMALS 1 



IT will be interesting and instructive to compare the 

 effects of the living bacillus, the dead cellular substance, 

 and the soluble poison on animals. 



The Action of the Living Bacillus. When a guinea-pig is 

 inoculated with a fatal dose of the living colon germ, prac- 

 tically no symptoms whatever are noticeable for a period 

 varying from five to twelve hours, according to the size 

 of the dose given. This may be considered as the period 

 of incubation and is roughly proportional to the amount of 

 living germ injected. We have always worked with a 

 bacillus 1 c.c. of a twelve-hour or older, bouillon culture of 

 which has invariably proved fatal to guinea-pigs within 

 twenty-four hours. If 1 c.c. of such a culture is given, no 

 effects will be seen for a period of from ten to twelve hours. 

 If, on the other hand, 2 c.c. of the same culture be injected, 

 the animal will begin to manifest symptoms of illness in 

 from eight to ten hours, and if larger doses are given the 

 symptoms will become apparent in a shorter time. This 

 period of incubation undoubtedly represents the time 

 taken for the bacillus to multiply and to be destroyed to 

 such an extent that sufficient poison may be liberated 

 through its disintegration to produce noticeable toxic 

 effects in the animal. This period of incubation is, therefore, 

 in reality the crisis of the disease and the outcome depends 

 solely on whether all bacteria have been destroyed before 

 a lethal dose of the poison has been set free or not. It is 



1 This chapter is a reproduction, without material change, of an article 

 by Victor C. Vaughan, Jr., published in the Jour. Amer. Med. Assoc. in 

 1905. 



