SYSTEMATIC AND DESCRIPTIVE. 137 



Genus II. Spirillum. 



Spirillum cholerae Asiaticse, (Comma-bacillu*) 



Koch. Curved rods, spirilla, and threads (Plate I., 

 Fig. 1 8). The curved rods or commas are about 

 half the length of a tubercle-bacillus. They occur 

 isolated, or attached to each other forming S-shaped 

 organisms or longer screw-forms ; the latter resem- 

 bling the spirilla of relapsing fever. Finally they 

 may develop into spirilliform threads. In old cul- 

 tivations threads are found with bulgings or irregu- 

 larities, which may be involution-forms (Plate L, 

 Fig- 35)-* The commas are actively motile ; their 

 movements and development into spirilla may 

 be studied in drop-cultivations. In plate-cultiva- 

 tions, at a temperature of from 16 20 C., the 

 colonies develop as little specks, which commence 

 to be visible after about twenty- four hours. Ex- 

 amined with a low-power, and a small diaphragm, 

 these colonies have the following characteristics. 

 They appear as little masses, granular, and of a 

 very faintly yellowish red tinge. They liquefy the 

 gelatine, and sink down in a little excavation, 

 at the bottom of which one recognises the puncti- 

 form colony. 



In test-tubes of slightly alkaline nutrient gelatine 

 (lop. c.), the appearance is strikingly distinctive. 

 The cultivation commences to be visible in about 



* Compare also Van Ermengem, Recherches sur le Microbe du 

 Choi. Asiat. i88s 



