Bacillus Coli Communis 523 



in 40 out of 50 cases depending upon Bacillus coli the blood 

 of the patient agglutinated the cultures obtained, not only 

 from his own stools, but from those of all the other cases. 

 From this uniformity of action Lesage suggests that the 

 colon bacilli in these cases are all of the same species. 



The agglutinating reaction occurs only in the early stages 

 and acute forms of the disease. 



Immunization. It is not difficult to immunize an 

 animal against the colon bacillus. Lofner and Abel im- 

 munized dogs by progressively increased subcutaneous 

 doses of live bacteria, grown in solid culture and suspended 

 in water. The injections at first produced hard swellings. 

 The blood of the immunized animals possessed an active 

 bactericidal effect upon the colon bacteria. The serum 

 was not in the correct sense antitoxic. 



Differential Diagnosis. This problem is considered at 

 greater length under the differential diagnosis of the Bacillus 

 typhosus (q. v.). For the recognition of the colon bacil- 

 lus the most important points are the motility, the indol 

 formation, the milk-coagulation, and the active gas-produc- 

 tion. As, however, all of these features are shared by other 

 bacteria to a greater or less degree, the most accurate 

 differential point is the immunity reaction with the serum 

 of an immunized animal, which protects susceptible animals 

 from the effects of inoculation, and produces a similar 

 agglutinative reaction to that observed in connection with 

 the blood and serum of typhoid patients, convalescents, 

 and immunized animals. 



The fact that, with rare exceptions, the typhoid serum 

 produces a specific reaction with the typhoid bacillus, and 

 the colon serum with the colon bacillus, should be the most 

 important evidence that they are entirely different species. 



I have no doubt that what is commonly known as Bacillus 

 coli communis is not a single species, but a name at present 

 applied to a group of bacilli too similar to be differentiated 

 by our present methods. This opinion seems to be shared 

 by others, and a separation into groups, types, or families 

 has been attempted. 



In order to establish a type species of Bacillus coli com- 

 munis, Smith* says: 



"I would suggest that those forms be regarded as true to this species 

 which grow on gelatin in the form of delicate bluish or more opaque, 



* " Amer. Jour. Med. Sci.," 1895, 110, p. 287. 



