DAIRY FARMING DAIRYING. 723 



number of bacteria per cubic ceutiuieter was less than 1,000. In the case of pas- 

 tcurizedtream this -was truoiu only 3 instances out of 29 (10 per cent). . . . 



"In only exceptional instances (not more than one or two in the entire set of 

 analyses) did the reduction in numbers fall below 90 per cent, showing;- t))at the 

 absolute ])erccntago of spores compared with gTowing- vegetating forms was very • 

 small. This proportion, however, is very largely dependent upon the manner in 

 which the milk is treated. If careless methods of milking prevail and much for- 

 eign matter, such as dirt and particles of excreta, be allowed to gain access to the 

 milk, the number of spores iu the milk is very much increased. This is another 

 foundation for the old argument of the effect of scrupulous cleanliness — a doctrine 

 so old and so often heard that it often falls unheeded to the ground."' 



The efl'ect of the age of the milk on the presence of spores is dis- 

 cussed. When the milk was received and handled promptly at the 

 creamery there was a much smaller number of organisms in it than 

 when it was from 30 to 42 hours old before handling, and the same was 

 true even in a more striking manner of the cream. Pasteurized milk 

 and cream showed only a few bacteria wlien made from fresh milk, but 

 contained considerable numbers of organisms when made from milk 

 kept from 1 to 2 days. 



"Data of this sort show that the age of the milk and the bacterial development 

 dependent upon this age account for the shorter kee])iug (jualities of the milk secured 

 under the more uniavorable winter conditions. This increased growth produces 

 naturally many spores, and therefore milk of this sort pasteurized with the same care 

 can not be expected to keep as well as that which is handled iu a fresher condition 

 wherc^ there are less bacteria in the spore or resistant form." 



Bejecting those species that occurred only sporadically in the cul- 

 tures, 15 difterent forms of bacteria were isolated from normal milk and 

 cream, 6 of which predominated in a large degree. Of these 15 forms, 

 3 species produced lactic acid, 7 species caused no apparent change in 

 the milk, and 5 species coagulated the milk by the production of rennet 

 and subsequently digested the curdled casein. In the same milk after 

 pasteurizing, only C species were isolated, 3 of which had no apparent 

 action on the milk, while the remaining 3 curdled the milk by the for- 

 mation of rennet and subsequently digested the same by the action of 

 a tryptic enzym. The species producing lactic acid were entirely 

 destroyed by pasteurizing. The species producing little or no acid are 

 believed to l^e derived from extraneous sources and to be associated 

 with dirt and excreta gaining access to the milk during the milking. 



"As these organisms that are thus associated with filth of various kinds are able 

 to persist in pasteurized milk by virtue of their spores, it emphasizes the well-known 

 lesson that scrupulous cleanliness is an absolute essential iu dairies that pasteurize 

 their )nilk for direct consumption. Cleanliness in milking diuiinishes materially the 

 amount of this class of bacteria that gains access to the milk." 



The effect of pasteurization and sterilization on the riscosity and fat 

 globules of milk and cream, F. W. Woll (pj). 1(54-173). — The object of 

 this investigation was to determine if possible the reason why milk or 

 cream heated to pasteurizing temperatures, or even lower, and subse- 

 quently cooled gives the appearance of being thinner than before and 



