BACILLUS CO LI . 355 



acetic acid and formic acid. Dextrose, lactose and mannite are thus 

 fermented; saccharose is not decomposed by the strains of the colon 

 bacillus commonly found in the intestinal tract. Occasionally a sac- 

 charose-fermenting strain is encountered in the feces. 1 



The reactions of the colon bacillus in milk are variable; typical 

 strains produce enough acid from the fermentation of the lactose to 

 cause an acid coagulation in one to three days at 37 C. Neutraliza- 

 tion of the acid by alkali redissolves the coagulum and the medium 

 resumes its normal appearance. Occasional strains do not cause 

 coagulation even after boiling the milk. 2 Gas is not produced in 

 appreciable amounts in milk by B. coli, and the organism leaves the 

 milk proteins practically intact even after prolonged incubation 



N f~f- ^\ i\\ . . . . <. T_ . V * 



FIG. 49. Bacillus coli, broth culture 



the carbohydrate constituents alone are acted upon. 3 Coagulation 

 does not as a general rule occur in litmus milk, but boiling the medium 

 usually causes rapid clotting. The ordinary litmus of commerce 

 contains considerable amounts of calcium carbonate. This may 

 neutralize some of the acid products of fermentation, reducing the 

 acidity below the coagulation point. This explanation does not 

 account for the same phenomenon in milk colored with pure litmus 

 or azolitmin. Gelatin is not liquefied by B. coli. Nitrates are reduced 

 to nitrites. 



(6) Enzymes. Soluble proteolytic and lipolytic enzymes have not 

 been detected in cultures of Bacillus coli. Buxton 4 has demonstrated 



1 Theobald Smith, Am. Jour. Med. Sc., September, 1895. 



2 Ibid., Fermentation Tube, p. 201. 



3 Kendall, Day and Walker, Jour. Am. Chem. Soc., 1914, xxxvii, 1945, 



4 Am. Med., 1903, vi, 137, 



