GENUS BACILLUS 313 



Milk. Milk coagulates in from four to ten days at 20 C. 

 and in from one to seven days at 37 C. The coagulation is 

 due principally but not altogether to acids. A ferment is 

 produced which is capable of causing coagulation in the pres- 

 ence of lime salts, especially in acid solutions. It is evident 

 also that the nature of this coagulation is more closely related 

 to coagulation fermentation than to simple acid fermentation, 

 from the fact that the colon coagulation forms a compact mass 

 which is with difficulty soluble in alkalies, and contains much 

 insoluble residue. In addition to albumose it has been shown 

 that milk serum, after colon coagulation, contains a substance 

 possessing the reaction of peptone, which is not contained in 

 the original milk. Similarly albumin cleavage products are 

 also formed in cultures of Bacillus coli in sugar-free ascitic 

 fluid ; it can not be assumed, therefore, that colon acidification 

 of milk, as such, produces this proteolysis. Savage 10 has 

 studied the coagulation of milk by B. coli and concludes that 

 the curdling is due in almost all cases to the formation of 

 acid, and that the enzyme plays little or no part in the initial 

 curdling, but it acts subsequently in converting the soluble 

 caseinogen into insoluble casein. O 'Hehir la failed in isolating 

 the enzyme but confirms the results of Savage. 



Life conditions and properties. B. coli is an aerobe and 

 facultative anaerobe. It multiplies slowly at room tempera- 

 ture, its optimum temperature is about 37 C. It is capable 

 of remaining alive for some time in water and soil. It pro- 

 duces indol. The toxic action is supposed to be due to the 

 poisonous substances contained within the bodies of the bac- 

 teria. Culture filtrates show very little toxicity when in- 

 jected into animals ; whereas the injection of dead bacilli pro- 

 duces symptoms almost equal in severity to those induced by 

 injection of the live microorganisms. Corroborative of the 

 assumption of this endotoxic nature of the colon bacillus 

 poison is the fact that, so far, no anti-toxic bodies have been 

 demonstrated in serum resulting from immunization. 



10 Savage. Jour, of Path, and Bact., Vol. X (1904) p. 90. 

 "O'Hehir. Jour, of Path, and Bact., Vol. XI (1906) p. 405. 



