BY R. GREIG SMITH. 443 



alkaline. Otherwise they appear to be the same organisms. The 

 difference is perhaps too slight to justify this being called a new 

 species. 



Bacterium gasoformans, Eisenberg. 



Bubbles of gas are formed in the depth of the ordinary solid 

 media. The cells are oval or sausage-shaped, and measure 

 05 : 1-2 ft.; they are actively motile. The colonies, on gelatine 

 plate, are circular and translucent white. Under a sixty-fold 

 magnification the surface colonies appear rounded with a slightly 

 erose margin; the centre is brownish and finely granular. The 

 contents of the colony appear in motion. At a later period the 

 contents become flocculent and the margin diffuse. In gelatine 

 stab culture the liquefaction is crateriform, then stratiform and 

 tubular. The stroke on agar is dirty-white, moist glistening and 

 at the base spreading Gas bubbles are formed in the agar. 

 On potato there is a scanty growth which is almost indistinguish- 

 able from the medium. Milk is coagulated, the reaction being 

 acid. Nitrates are reduced to nitrites. 



Bacterium aurescens, Ravenal. 



This motile organism is oval, and measures - 3-0 - 4 : 1 p. It 

 forms threads in old cultures. In agar stroke culture the first 

 growth is a thin yellowish-white line, which as it broadens becomes 

 primrose-coloured, and ultimately of an old-gold shade. In 

 gelatine stab culture there is a filiform growth; the gelatine at 

 the upper part of the stab becomes slightly consumed, and 

 eventually the growth around the consumed portion becomes 

 tuberculate and yellowish-white. The colonies on gelatine are 

 yellowish, and slowly liquefy the gelatine. Under a sixty-fold 

 magnification they are seen to have a lacerate, transparent margin, 

 and a pale yellowish-brown, marbled or convoluted centre. The 

 older surface colonies have the central convolutions more marked, 

 an annulus with coarse flakes floating in the liquefied medium, 

 and a ciliate margin. The deep colonies are brown and rounded. 



