NOT DESCRIBED IN PREVIOUS SECTIONS. 449 



much alike. All are good anaerobic growers ; all form gas ; all turn milk 

 distinctly acid ; and all closely resemble one another in pure cultures. Many 

 would doubtless class these altogether as one species ; but if species are to 

 be recognized at all, we must come to recognizing every fixed difference as 

 constituting a species. 



" This group occurred always very abundantly in eighteen out of the 

 twenty- two cases of summer diarrhoea, and is also well represented among 

 the kittens. They are, however, so much like the harmless forms found by 

 Escherich that they may for the present be laid aside as of no specific sig- 

 nificance. They are also almost the only forms tested which failed to pro- 

 duce intestinal troubles in kittens. Excluding these, there is no species, or 

 group of species, left either generally occurring or in sufficient numbers to 

 be regarded as the specific pathogenic plant of summer diarrhoaa." 



92. BACILLUS ACIDIFORMANS. 



Obtained by the writer (1888) from a fragment of yellow-fever liver pre- 

 served for forty-eight hours in an antiseptic wrapping ; since obtained from 



FIG. 150. FIG. 151. 



Fi. 150. Bacillus acidiformans, from a potato culture. X 1,000. From a photomicrograph* 

 (Sternberg.) 



FIG. 151. Culture of Bacillus acidiformans in nutrient gelatin, end ofjfour days at 22 C. 

 From a photograph. (Sternberg.) 



liver preserved in the same way from two comparative autopsies i.e., not 

 cases of yellow fever. 



Morphology. A short bacillus with rounded corners, sometimes short 

 oval in form ; from li to 3 y" in length and about 1.2 # in breadth ; may grow 

 out into filaments of 5 to 10 jj. , or more, in length ; in some cultures the short 

 oval form predominates. 



Stains readily with the aniline colors usually employed, and by Gram's 

 method. 



Biological Characters. An aerobic and facultative anaerobic, non- 

 liquefying, non-motile bacillus. Does not form spores. Grows rapidly at 

 the room temperature in the usual culture media. Grows in decidedly acid 

 media; in culture media containing glycerin or glucose it produces an abun- 

 dant evolution of carbon dioxide, and a volatile acid is formed. 



It does not liquefy gelatin, and in stick cultures grows abundantly both 

 on the surface and along the line of puncture. At the end of twenty-four 

 hours, at 22 C., a rounded white mass is formed upon the surface, resembling 



