DAIRY FARMING! DAIRYING. 575 



or 50 per cent, withstood the heating process. All the streptococci from milk 

 and cream were destroyed by heating to 73.9° for 30 minutes. 



" Among the 139 cultures of streptococci there were 22 that formed long 

 chains, which, for the purpose of this paper, were considered as typical strep- 

 tococci. The others were considered atypical. The typical streptococci were 

 much less resistant to heat than were the atypical. Of the 22 typical strep- 

 tococci 12, or 54.54 per cent, survived heating for 30 minutes at 57.2° ; at 60° 

 9, or 40.91 per cent, survived; at 62.8° only 1 culture, or 4.54 per cent, withstood 

 the heating. All of the typical streptococci were destroyed by heating for 

 30 minutes at 65.6°. The 117 atypical streptococci were more resistant; at 

 60° 68.37 per cent survived; at 62.8° 38.46 per cent survived; and at 71.7° 

 2.56 per cent survived; all were destroyed at 73.9°. 



"Two classes of streptococci seem to survive pasteurization: (a) Strepto- 

 cocci which have a low majority thermal death point but among which a few 

 cells are able to survive the pasteurizing temperature. This ability of a few 

 bacteria to withstand the pasteurizing temperature may be due to certain re- 

 sistant characteristics peculiar to a few cells or may be due to some protective 

 influence in the milk, (b) Streptococci which have a high majority thermal 

 death point. When such is the case, the bacteria survive because the majority 

 thermal death point is above the temperature used in pasteurization. This 

 ability to resist destruction by heating is a permanent characteristic of certain 

 strains of streptococci. The thermal death point determinations in this work 

 were made in milk in such a manner as to represent actual conditions of pas- 

 teurization by the holder process ; therefore the results show what may be ex- 

 pected in commercial pasteurization, and it is evident that some streptococci 

 may survive the process. However, different results might have been obtained 

 if a lai'ger number of cultures had been studied and if other methods and 

 media had been used for determining the thermal death points." 



The application of refrigeration to the handling of milk, J. T. Bowen 

 {U. S. Dept. Agr. Bui. 98 (1914), pp. 88, figs. 37).— This bulletin discusses the 

 application of refrigeration in the operation of the modern milk plant and 

 describes the various forms of mechanical and other systems of cooling. 



After treating of the physical changes, including specific heat, cohesion, 

 viscosity, and coefficient of expansion and freezing, and the bacteriological 

 changes of milk and cream the author takes up a discussion of the principles 

 involved in cooling by means of salt and ice mixtures. Curves are given show- 

 ing the approximate temperature obtained with different . proiwrtions of salt, 

 the refrigeration available with different percentages of salt, and the specific 

 heat of common salt brine with difi:erent percentages of salt. The ice bunker, 

 gravity brine, compression and vapor absorption systems of refrigeration are 

 treated, together with their installation and operation. Methods of utilizing 

 refrigeration described are the direct expansion, brine circulating, brine storage, 

 congealing tank, and air-circulating systems. 



Other subjects discussed are insulation, size and cost of plants, and cooling 

 milk on the farm, during transportation, and at the receiving stations, bottling 

 plants, and creameries. 



A study of the market butter of Boston, M. J. Rosenatt, W. D. Frost, and 

 Ruth Bryant {Jour. Med. Research, 30 {1914), No. 1, pp. 69-85). — Twenty-five 

 samples of butter, representing the market supply of Boston and scoring from 

 SO to 98, were studied. 



There appeared to be no definite relation between score and price. Attempts 

 were made, without success, to devise a practical dirt test for butter. 



The average number of bacteria per gram was determined by emulsifying 

 the butter in warm water. The average number for the 25 samples was 



