448 APPLICATION OF METHODS OF BACTERIOLOGY 



characteristic about it. This is true both for smear-cultures 

 and for single colonies. 



Its growth on gelatin is much less voluminous than on 

 media that can be kept at higher temperature, though it 

 does grow on this medium at room-temperature without 

 causing liquefaction. 



Its growth on blood-serum is in the form of a moist, 

 opaque, slimy layer, inclining to a yellowish or dirty, 

 brownish-yellow tinge. It does not liquefy the serum. 



On potato its growth is moderately rapid, appearing in 

 from twenty-four to thirty-six hours at 37 C. as a moist, 

 amber-yellow, transparent deposit having somewhat the 

 appearance of honey; this becomes deeper in color and 

 denser in consistence as growth progresses, and finally takes 

 on a reddish-brown color; at the same time the potato 

 about it becomes darkened. 



In bouillon it causes diffuse clouding, with ultimately the 

 formation of a more or less tenacious or ropy sediment. 



In milk to which a little litmus has been added it causes 

 the blue color to become red or reddish in from four to five 

 days, and quite red after two weeks at 37 C. At the same 

 time the milk separates into clear whey and a firm clot of 

 casein. 



Its reactions to heat are very interesting. At 42 C. it 

 will often grow for twenty days or more. It will not grow 

 at 43 C., and if exposed to this temperature for forty-eight 

 hours it is destroyed. It is killed in five hours when exposed 

 to 50 C., and in five minutes by 55 C. 



It grows both with and without oxygen; it is therefore 

 facultative as regards its relation to this gas. 



On cover-slips it stains readily with all the basic aniline 

 dyes, and, as a rule, as stated, presents conspicuous irregu- 



