PATHOGENIC BACTERIA. 317 



Shiga does not; they also differ from it in their agglutina- 

 tion reactions.* 



Spirillum cholerae Asiaticse (Comma Bacillus of Cholera).— 

 A rod-shaped organism, somewhat curved, and with pointed 

 ends, hence the name, "comma" bacillus. The curved forms, 

 placed end to end, may produce an S-shaped body. The 

 length is from 0.8 to 2 /i and the breadth from 0.3 to 0.4 /i. 

 In cultures some individuals may develop into genuine spirilla. 

 In the whitish particles found in the stools of cases of cholera 

 the organisms may be present in very large numbers. In these 

 particles they may exhibit a very curious arrangement, lying 

 parallel with one another, and, as remarked by Koch, they 

 resemble a school of fish moving up stream. Involution 

 forms, irregular in outline and staining poorly, are often seen 

 in old cultures. The organism is motile, having a flagellum 

 at one end. It does not form spores. It stains with the ordinary 

 anihne dyes, but not by Gram's method. It is aerobic. It 

 grows at the room-temperature, but better in the incubator. 

 On the ordinary media the growths are whitish. It grows best 

 on neutral or alkaline media, and is very sensitive to a small 

 amount of acid. It liquefies gelatin. The colonies on gelatin 

 plates have a very characteristic appearance. They are nearly 

 round at first, and granular as seen under the low power of the 

 microscope; but at the end of about twenty-four hours the 

 outhne is slightly irregular, and the surface looks as though 

 it were covered with finely broken glass. The outline later 

 becomes still more irregular or scalloped. As Hquef action of 

 the gelatin takes place a funnel-shaped depression is formed, 

 into which the colony sinks. Gelatin plates should be kept 



* Shiga. Ceniralblatt jur Bakteriologie. Bd. XXIV. 1898. Flexner. 

 Philadelphia Medical Journal. September i, 1900. Vedder and Duval. 

 Journal Experimental Medicine. Vol. VI. Gay. University of Pennsylvania 

 Medical Bulletin. November, 1902. Duval and Bassett. American Medi- 

 cine. Vol. IV. P. 417. 1902. Park and Carey. Journal Medical Research. 

 Vol. IX. 1903. Strong and Musgrove. Journal American Medical Associa- 

 tion. Vol. XXXV. P. 498. 1900. 



