DAIRY FARMING DAIRYING. 675 



act simply by raising the hydrogen ion concentration nor the latter from its 

 effect upon the soluble calcium content. The acid precipitation zone of 

 caseinogen lies on tlie acid side of the rennin zone of action, but the latter 

 gradually approaches the former as the calcium content of the mixture is 

 lowered, so that in all probability the latter is an extension of the former 

 toward tlie neutral point. Calcium chlorid, apart from its effect upon the 

 hydrogen ion concentration, increases tlie activity of tlie rennin ferment from 

 the beginning of the digestion process." 



Relation of numbers of Streptococcus lacticus to amount of acid formed 

 in milk and cream, P. G. Heinemann {Ahs. in Science, n. ser., J^2 {1915), No. 

 1079, p. 321). — Flasks of both sterilized and raw milk and cream inoculated with 

 S. lacticus were incubated at temperatures of 37, 20, and 7° C. and the 

 bacteriological results compared with flasks left to sour spontaneously. 



It was found that " the amount of acid formed during the souring process of 

 milk or cream is not solely dependent upon the number of bacteria present of 

 the S. lacticus group. Temperature and the presence of other bacteria may 

 influence the result. In raw milk or cream or in raw milk or cream inocu- 

 lated with cultures of <S. lacticus the number of bacteria increases to a given 

 point and then decreases. The higher the temperature up to 37" the earlier 

 is the maximum number reached. Coagulation of milk or cream is not de- 

 pendent solely upon a certain amount of acid or a certain number of bacteria. 

 After the decline in numbers the amount of acid continues to increase, probably 

 due to enzym action. At 37° extraordinarily large amounts of acid may be 

 formed, due probably to the presence of members of the group of lactobacilli." 



The alkali-forming- bacteria found in milk, S. H. Ayers and P. Rupp {Ahs. 

 in Science, n. ser., 1^2 (1915), No. 1079, pp. SIS, 319).— A brief account. 



The preservation of milk by freezing, G. Fascetpi {Staz. Sper. Agr. Ital., 

 48 (191.5), No. 1, pp. 61-65). — A discussion of the effect of freezing upon the 

 pliysical characteristics of milk. 



The refrigeration of a city's milk supply, C. Bates {Abs. in Science, n. ser., 

 ^ {1915), No. 1079, p. S19). — In bacteriological examinations of a city's milk 

 supply the Bureau of Chemistry of this Department has found that the chief 

 cause of high bacteriological counts was due to nonrefrigeration of milk in 

 transit, the average temperature of the milk upon receipt in the city being 

 about 65° F. This milk was en route from 6 to 12 hours. Refrigeration 

 has now been provided by the railroads, and the milk at the present time is 

 being received in the city at about 48°. 



Factors influencing the resistance of lactic acid bacteria to pasteurization, 

 K. Reiser {Ahs. in Science, n. ser., 42 {1915), No. 1079, p. 320). — In milk and 

 cream pasteurized at 63° C. were found a number of strains of the Bacterium 

 lactis acidi type, whose thermal death point in broth is below the pasteuriza- 

 tion temperature. The average thermal death point is in whole milk 5°, in 

 separated milk 2.5°, and in whey 0.5° higher than in bouillon. These results 

 indicate that the protection given to the suspended lactic bacteria by the casein 

 and coagulated albumin of separated milk raises their thermal death point 2.5° 

 and that the protein and fat of whole milk raises their thermal death point 5°. 



Silicic acid in milk from sterilization in glass bottles, B. Pfyl {Mollc. Ztg. 

 Berlin, 25 {1915), No. 23, pp. 177, J[78).— Ordinarily there is from 0.8 to 1.1 mg. 

 of silicic acid (SiOj) per 500 cc. of milk. When milk is sterilized in glass 

 bottles there is an increase of from to 0.7 mg., depending upon the condition 

 of the bottles. 



[Waste in milk delivery] {V. S. Dept. Agr., Weekly News Letter, 2 {1915), 

 No. 51, pp. 1, 2). — From data collected by the Dairy Division of this Department 



