PUTREFACTIVE ORGANISMS 105 



transparent ; later the gelatine is rapidly liquefied, the colonies 

 producing shallow cup-like depressions in twenty-four hours or 

 less at 22 C. The stab is thread-like at first; afterwards a 

 cylinder of turbid liquefied medium is seen, with a cup-shaped 

 depression at the surface. 



Agar. The colonies on agar are thin, bluish-grey, and semi- 

 transparent ; at first round, but irregular later and extending over 

 the whole surface. 



Potato. Little growth, yellowish- white. 



bouillon. Turbid throughout, with an abundant sediment in 

 twenty-four hours. 



Sugars. Ferments grape and cane sugars with the production 

 of CO 2 and H 2 (i : 2) ; no gas from lactose. 



Milk. Casein is coagulated in two or three days, and after- 

 wards dissolved, with the production of a slightly acid yellow 

 liquid. 



Proteus mirabilis, Hauser, is a form of Bact. vulgare which 

 readily produces pear-shaped or rounded involution forms 4 to 7 ^ 

 in diameter. The colonies on gelatine and agar are similar to 

 those of the typical species, but the former medium is more 

 slowly liquefied. 



Proteus Zenkeri, Hauser, is also a variety of Bact. vulgare it 

 does not liquefy gelatine and grows best at 30 C. The surface 

 colonies on gelatine spread out in star-like forms, and the stab 

 shows characteristic thread-like growths all round the track of the 

 needle. 



2. Very closely resembling Proteus Zenkeri is Bacterium 

 Zopni, Kurth, originally isolated from the dung of fowls, and 

 since found commonly in putrid substances and impure water. 

 It is motile and varies much in form, very short rods and long 

 threads being obtained. Under certain unfavourable conditions 

 the threads break up into -round coccus-like cells, which develop 

 again into rods when placed in suitable nutrient media. The 

 colonies do not liquefy gelatine but grow outwards in delicate 

 irregular branches, the whole looking like the mycelium of a 



