I TJNIVERSIT" 



Mlcrohic Diseases Individually Considered. 331 



and transforming the lactose into a mucilaginous 

 substance which gives to the milk its peculiar con- 

 sistence. 



Blue milk. — It sometimes happens that m.ilk, from 

 twenty to thirty-six hours old, shows on its surface 

 small light-blue patches which, later, take an indigo- 

 blue shade. These patches increase in area as w^ell 

 as in depth although never exceeding the thickness 

 of the cream. Such milk is highly subject to change; 

 it quickly becomes acid, coagulates and then putre- 

 fies. 



The causative agent of blue milk is the bacillus 

 cyanogenus. This is a motile rod, 2/j. to 4/x long by 

 0-5/i thick, commonly isolated but sometimes united 

 in a zooglcea. The spore which it produces is a 

 little larger than the bacillus giving to the latter a 

 club or spindle-shaped appearance. In certain artifi- 

 cial media it assumes very diverse involution forms — 

 balloon and ribbon shapes, etc. Grown on the gela- 

 tin plate it forms, after tw^o days, small whitish spots 

 which soon extend over the whole surface giving it 

 a bluish color. Stab cultures in gelatin show whitish 

 colonies on the surface and steel blue in the depth. 



When inoculated to milk it increases the alkalinity 

 of the latter and the layer of cream becomes slate 

 colored, this tint turning to blue on the addition of 

 acid.' If the milk has not been sterilized the lactic 

 acid fermentation which goes on at the same time 

 supplies the acid by which the blue color is pro- 

 duced. 



The germ multiplies in albuminous solutions con- 

 taining lactate of ammonia, without producing the 

 coloring principle. 



