MILK ANOMALIES. 83 



grees C. and which therefore retain their full vitality in 

 milk sterilized according to the usual method. [Moreover, 

 their presence is unnoticed in fresh milk kept at ordinary 

 temperature or in boiled milk ; their influence, however, is 

 noticed when imperfectly sterilized milk is kept at t^J de- 

 grees in an incubator. Such milk, or sterilized milk in- 

 oculated with pure cultures of peptonizing bacteria, 

 shows profound changes after standing from one 

 to five days. Beneath the cream zone a trans- 

 parent zone is formed which appears to be made 

 up only of serum. Gradually the transparent zone 

 becomes wider, the casein not \et peptonized be- 

 gins to separate into flakes, and in most cases 

 rennet fermentation occurs in addition. Milk s(i 

 changed, has a bitter, pungent, peptone-like taste. The 

 identification of individual species jjrcscnts great ditti- 

 culty. It is not possible to recognize them through cul- 

 tures upon agar and gelatine plates, but identification is 

 usually successful through cultivation upon potatnes, ab- 

 solutely sterile skimmed milk, alkaline _<;clatine, and sticl^ 

 culture in sugar agar. Often these methods fail and it is 

 necessary to study the metabolic assiniilatiim and the 

 thermal death point of the germ to assure an accurate 

 diagnosis. 



(An accurate and detailed description of all the characteristics 

 of the bacteria mentioned above is found in "Fluegge's Zeit- 

 schrift fuer Hygiene and Infectionskrankheiten. Vol. X\'II, 

 292.") 



Abnormal milk with neutral or alkaline reaction fre- 

 quent!}' becomes curdled, due to the presence and the ac- 

 tion of the bacteria just mentioned. Normal sour curdling 

 is caused by a series of widely diffused kinds of bacteria, 

 viz : the Bacillus acidi lactici Hueppe ; Bacterium acidi 

 lactici Grotenfeld; Bacterium limbatum acidi lactici 

 Marpmann : Bacillus acidi lactici Leichmann ; Micro- 



