314 MANUAL OF BACTERIOLOGY. 



ing neutral red become yellow, as with B. coli communis, but more slowly, and 

 the red color sometimes returns. In respect to the fermentation of saccharose 

 and the formation of indol reports differ; both are usually negative. The 

 blood of the patient agglutinates the bacilli. But, as among the closely related 

 members of this group mutual reactions are sometimes seen, this test is not 

 to be considered invariable.* Several bacilli allied to the above are known. 

 The Bacillus enteritidis of Gaertner is a related form which has been found 

 in cases of meat-poisoning. 



Bacillus lactis aerogenes (Bacillus aerogenes). — ^A ba- 

 cillus having a form similar to that of the colon bacillus, de- 

 scribed as being larger and plumper. In the main its proper- 

 ties are similar to those of the colon bacillus. Its colonies 

 are more circumscribed and elevated than those of the colon 

 bacillus. It is non-motile. It coagulates milk more rapidly 

 than the colon bacillus. It produces gas upon potato more 

 rapidly than the colon bacillus, and more abundantly. It was 

 first described by Escherich, who discovered the colon bacillus, 

 assigning the Bacillus lactis aerogenes rather to the upper part 

 of the small intestine, and the colon bacillus to the lower portion. 

 According to Kruse, the Bacillus lactis aerogenes and its rela- 

 tives differ from the Bacillus coli communis chiefly in lacking 

 motility. like the colon bacillus it has been found many 

 times in the urine in cystitis. See also B. acidi lactici, page 

 225. 



Bacillus dysenteriae (Shiga). — A bacillus with rounded 

 ends, of the size and shape of typhoid and colon bacilli, seldom 

 forming threads. Most observers have found it non-motile. 

 Vedder and Duval have demonstrated fiagella. The bacillus 

 does not form spores. It may be stained with the ordinary 

 aniline dyes; it does not stain by Gram's method. It is a facul- 

 tative anaerobe. It grows at ordinary temperatures, but better 

 in the incubator. It grows on the usual culture-media, but more 



* Gushing. Bulletin Johns Hopkins Hospital. July-August, 1900. Strong. 

 Ibid. May, 1902. Johnstone, Hewlett and Longcope. American Journal 

 Medical Sciences. August, 1902. Libman and Buxton. Journal Medical Re- 

 search. Vol. VIII. 1902. 



