BACILLUS CO LI COMMUNIS. 451 



by experiment that 1 c.c. of a fresh bouillon culture 

 of the B. coli from normal feces was required to kill 

 guinea-pigs by intraperitoneal and rabbits by intraven- 

 ous injection, whereas less than one-fifth as much of a 

 culture from a fatal case of cholera nostras was suf- 

 ficient to kill the same animal; but this rule has prob- 

 ably many exceptions, even if it be true in some cases. 



All observers, however, agree that the virulence 

 of the B. coli is diminished by continued cultivation 

 through successive generations, and that it is increased 

 by passage through animals. 



Immunization. Immunization against colon infec- 

 tion is comparatively easy to produce in the usual way 

 by the inoculation of gradually increasing doses of 

 cultures of the living bacilli or dead bacilli. 



Occurrence in Man and Animals. The bacillus coli 

 communis is a common inhabitant of the intestinal 

 canal in man and in many animals. According to 

 Fremlin, it is found normally in dogs, mice, and rab- 

 bits, but not in rats, pigeons, or guinea-pigs. Accord- 

 ing to Dyas and Keith, it occurs in goats, rabbits, dogs, 

 cats, swine, and cows, but not in horses. Grimbert 

 claims to have found it in the intestines of almost all 

 domestic animals, and in the mouth as well as the in- 

 testines of man. It is also frequently found in water 

 and food (milk, etc.), so that it is one of the most wide- 

 spread saprophytic bacteria known. Formerly it was 

 thought that the presence of the B. coli in water was 

 sufficient proof of its contamination by feces; but the 

 recent investigations of Weichselbaum, Kruse, Beck- 

 mann, and Refith would seem to show that there are 

 no grounds for this assumption, as the colon bacillus 

 may reach the water from many different sources. 



