174 EXPEEIMENT STATION RECORD. 



of the various roughages, concentrates, and commercial feeds especially adapted 

 to South American conditions. 



Holstein milk yield, F. R. Marshall (Jour. Heredity, 5 (1914), No. 10, pp. 

 Jf37-43!)}.—Jn ooiitiuuution of work previously reported (E. S. R., 27, p. 574) the 

 author presents the results of examinations made by P. Van Ewing of the 

 records of Holstein cattle, in which it appeared that the idea that milking 

 capacity in cows is transmitted through males rather than females is erroneous. 

 The number of cases in which resemblance was closest on the maternal side 

 wei-e for pounds of milk 403, pounds of milk fat 407, and percentage of milk fat 

 345, while the number of cases in which resemblance was closest on the paternal 

 side were 262, 258, and 320, respectively. 



Studies in the range of variation of the percentage of butter fat in the 

 milk of individual cows, A. C. Andkhson (Michif/an Sta. Spec. Bui. 11 (1914), 

 pp. 3-13, figs. 5). — In a study of 200 seven-day records of dairy cows it was 

 found that 27.5 per cent varied not over 1 per cent in milk fat in the seven days, 

 44 per cent varied between 1.1 and 2, 21.5 per cent between 2.1 and 3, 4 per 

 cent between 3.1 and 4, 1.5 per cent between 4.1 and 5, and 0.5 per cent between 

 5.1 and 6. In a study of 2,000 seven-day records of cows on advanced registry 

 tests the percentages were as follows: 28.45, 54.55, 13.4, 2.65. 0.8, and 0.15. 

 In 600 two-day records the percentages were 74.3, 20.1, 4.6, 0.5, and 0.3. 



Some investig'ations on the phenomena of " clot " formations. — I, On the 

 clotting- of milk, S. B. Schryver (Proc. Roy. Soc. [London], Scr. B, 86 (1913), 

 No. B 590, pp. 460-481; ahs. in Jour. Chem. Soc. [LondoWi, 104 (1913), No. 612, 

 II, pp. 850, 851). — In milk the substances necessary for clot formation preexist, 

 but the adsorption of simple molecules from the solution prevents aggregation. 

 In this work it is assumed that the ferment clears the surface of colloid from 

 adsorbed substances and allows aggregation to take place. 



The addition of calcium chlorid to solutions of caseinogen in sodium hydroxid 

 gives a precipitate only within certain definite limits of concentration of the 

 calcium salt. Rennet, when added to a mixture in which precipitation is in- 

 hibited by an excess of the calcium salt, immediately causes precipitation. 

 When the optimal amount of calcium salt is present precipitation may be pre- 

 vented by adding milk serum, peptone, or glycin. Rennet precipitates only 

 when a proper amount of inhibitor is present ; an excess prevents precipitation. 

 The clot is formed from caseinogen and not from the calcium salt. 



"The clot produced by rennet alone is formed from metacaseinogen ; that 

 produced by calcium chlorid alone is formed from caseinogen. The rennet clot 

 can not be converted into natural caseinogen. The rennet does not in any way 

 affect proteoclastic digestion in the clot. In milk the clot formation depends on 

 the presence of four series of substances in the system, namely, simple inhibitory 

 substances, colloids, enzyms, and calcium salts." 



The growth and viability of streptococci of bovine and human origin in 

 milk and milk products, D. J. Davis (Jour. Infect. Diseases, 15 (1914). No. 2, 

 pp. 378-388). — From investigations made in connection with epidemics of sore 

 throat it appeared that all the streptococci causing the epidemic were of the 

 hemolytic variety. A study of these showed that " in the process of milk sour- 

 ing the growth of hemolytic streptococci is inhibited and the organisms are 

 gradually destroyed. I They are killed in three hours or less by the acidity of 

 sour milk (48 hours''. after curdling) and of buttermilk. In ordinary butter 

 they die in the course of a few days, due to the acidity, although in neutral but- 

 ter they live for a long time. In ice cream, hemolytic streptococci remain alive 

 for at least 18 days without any appreciable diminution in number or virulence. 

 Ice cream would seem to be. therefore, a most suitable medium for the trans- 

 mission and preservation of dangerous streptococci. Separator cream contains 



