RopiNEvSS IN Milk AND Cream. 411 



Milk. — The cream on the surface of milk becomes noticeably 

 viscid in twelve hours after inoculation. The milk below, while 

 plainly ropy in 3'oung cultures, does not exhibit the maximum 

 viscosity until several weeks have elapsed. In old cultures the 

 milk will spin out in opalescent, gossamer-like threads frequently 

 a yard long. If one of these fine threads be allowed to come in 

 contact with a cover-glass and be examined microscopically, the 

 milk will be found swarming with bacteria arranged in long 

 chains. Only after considerable evaporation has occurred do 

 milk cultures assume a semi-fluid consistency. The reaction, at 

 first alkaline to litmus, becomes feebly acid after about two 

 months. 



In separator skim milk, additional appearances become appar- 

 ent, due probably to the relatively smaller per cent of fat present. 

 The milk promptly becomes viscid like whole milk, and remains 

 so during the succeeding changes. After about a month the 

 liquid gradually becomes translucent and opalescent throughout. 

 This appearance, together with the alkaline reaction and the entire 

 absence of fat globules, shown upon microscopic examination, 

 indicates that saponification has occurred. In some cultures this 

 change has been observed to occur first at the surface and 

 later to extend downwards in a gradually broadening zone. A 

 relatively large deposit of white precipitate occurs. 



hidol. — An indol reaction is doubtful. 



Thermal Death Point. — Freshly inoculated bouillon cultures 

 remain sterile after exposure to a temperature of 58° C. for ten 

 minutes. Exposure for the same length of time to a temperature 

 one degree less, fails to kill the organism. 



Disinfectants. — Duplicate tests conducted during the month of 

 October show that a drop of buillon culture dried upon a cover- 

 glass is rendered sterile by exposure to direct sunlight for three 

 hours. Experiments conducted during January show that seven 

 hours are required to accomplish the same result in mid-winter. 

 Bacteria from a bouillon culture dried upon cover-glasses, have 

 retained their vitality for a month when kept in the dark. 



Experiments with a solution of powdered soap widely used in 

 creameries do not indicate that that substance possesses disin- 

 fecting powers in the strength ordinarily used in dish washing. 



