DAIRY FARMING DAIRYING. 987 



Iii each of 26 experiments 2 bottles of tlie pasteurized milk and 2 bot- 

 tles of the same milk unpasteurized were taken as samples, one set being- 

 tested for acidity and tbe resistant bacteria and the other set being 

 kept until it spoiled. The data for these samples are given. From the 

 pasteurized inilk 30 varieties were isolated and studied. The charac- 

 teristics of ID varieties are given, since these are believed to be repre- 

 sentative of the whole. The source of these resistant bacteria was 

 studied by making numerous plate cultures of the dust in the air of the 

 stable, the animal, etc. From these bouillon cultures were made of the 

 different kinds of bacteria, and these cultures were pasteurized. Of 

 those which resisted pasteurization 2 were from the dust of the stable, 

 2 from the dirt from the cow, 1 from the dairy, and 3 from the first part 

 of the milking. 



As to the effect of these resistant bacteria on the milk after pasteuri 

 zatiou, it was found that some only curdled the milk, some peptonized 

 the casein, some did both, while others produced no perceptible change 

 in the milk. 



A special experiment on the thermal death point of tubercle bacilli 

 showed that heating the milk containing them at 08° C. for 20 minutes 

 destroyed the bacilli, so that the milk had no injurious effect when inoc- 

 ulated into guinea pigs. A study of the thermal death points of the 

 resistant bacteria showed that 17 of the 10 forms were not killed by a 

 temperature of 80° C. for 20 minutes; 6 remained alive after heating 

 the same time at 00° (J., and 1 at 06° C, but all were killed by boiling 

 20 minutes. The effect of sudden cooling after pasteurization upon of 

 the resistant varieties was studied in a series of tests on bouillon cul- 

 tures of these bacteria. In each case one culture was cooled suddenly 

 to 8° O. and another allowed to cool gradually to the temperature of 

 the room, the time required for development being noted in each case. 



"In this work 10 cultures of the suddenly cooled exceeded the time of 

 development of the noncooled; 12 cultures of the noncooled or cooled 

 gradually exceeded the time of development of the cooled; 6 cultures of 

 the suddenly cooled developed in the same time as the noncooled. Sud- 

 den cooling seems to have no effect on the time of development." 



The restraining influence of keeping at a low temperature on develop- 

 ment was shown in trials with the same G species. Six miscellaneous 

 micro-organisms were treated in the same way but not subjected to 

 pasteurization. Here it was noticed that the time of development was 

 retarded several days by placing them in the refrigerator. The effect 

 of contiuued heat in restraining development Avas illustrated in trials 

 with the 6 same cultures. When the 6 cultures were pasteurized and 

 then kept in a refrigerator very few of the germs developed in 45 days. 



In conclusion, remarks are made on the value of pasteurization, 

 especially in preventing contagious diseases and intestinal disorders of 

 young children. 



Quick and slow ripening of cream, Gr. L. McKay and G. H. Eckles 

 (Iotca Sta. Bui. 35, pp.820S22). — Nine trials were made, beginning the 



