366 THE MUCOSUS CAPSULATUS GROUP 



Bacillus Lactis Aerogenes. This organism is an almost constant 

 inhabitant of the upper part of the intestinal tract of nurslings; it is 

 common in the intestinal contents of bottle-fed infants, and it fre- 

 quently persists in small numbers in the adult intestinal tract. A 

 closely related organism, Bacillus acidi lactici, is found fairly widely 

 distributed in milk, water, and sewage. A sharp differentiation between 

 the two organisms is difficult to establish. There is evidence that 

 the organism, ordinarily a harmless intestinal parasite, may become 

 temporarily pathogenic and incite intestinal disturbance varying in 

 intensity from slight diarrhea to severe enteritis. 1 Occasional cases 

 of cystitis in infants are also associated with the presence of Bacillus 

 lactis aerogenes in pure culture. 



It is obvious that the interrelations of the Mucosus Capsulatus Group 

 are at present in an unsatisfactory state attempts to separate the 

 organisms on the basis of serological reactions have been unsuccessful, 

 partly because of the difficulty of removing the capsules which appear 

 to be somewhat impervious to antibodies. A final arrangement of 

 the group and an ultimate differentiation of the various organisms 

 comprising it awaits future elucidation. 



1 Kendall and Day, Boston Med. and Surg. Jour., 1913, clxix, 753; Kendall, ibid., 

 May 20, 1915. 



