DAIHY FARMING DAIRYING. 79 



The variation in the composition of milk. A. Lauder (Edinh. and Ea.st of 

 f<cot. Col. A(ji: Bui. I'l, pp. 3'i). — The iireseiit report contains the results oh- 

 tained from July, 1906, to July, 1007, in continuation of work previously re- 

 jiorted (E. S. R., IS, p. 7GS). Data rejiarding the yield of 22 cows of the 

 ordinary dairy Shorthorn type, varying in age between G and 10 years, are 

 given. On several occasions the mixed milk of the herd contained little more 

 than 3 per cent fat, but it never fell l)elow that standard. The 11 cows that 

 remained in the herd throughout the entire year gave an average yield of 885 

 gal. of milk, with an average fat content of 3.49 per cent for the morning milk- 

 ing and 3.98 per cent for the evening milking. 



Variations in the amount of casein in cows' milk, E. B. Hart ( Wisconsin 

 stn. Rpt. 1907. pp. lU-llC)). — This article has been abstracted from another 

 source (E. S. II.. 19, p. 77G). 



The chemistry of milk curdling, J. I.. Sammis {Wisconsin Htn. Rpt. 1901, 

 pp. J7J-1S9. fif/s. 10). — From the d:ita reported the author draws the following 

 deductions : 



"The coagulation of milk by different acids at fixed temperature requires 

 quantities of the acids which are not chemically equivalent to each other. 



" The quantity of any acid required to coagulate a given sample of milk is 

 less at high temperature than at low temperature. 



"Variations in the proportions of neutral salts, or water, or sugar, as well as 

 acids, present in milk produce variations in the coagulation temperature of the 

 milk. In alkaline milk, neuti'al salts affect the curdling temperature. 



"The reaction of lime-water casein solutitm with acid, producing a milky 

 white appearance, is shown to be strongly dependent on temperature. 



" The theories of Hammarsten, Soelduer, Van Slyke, and Hart, and others to 

 the effect that milk as well as lime-water casein solutions contain a compound 

 of casein with one other milk constituent, as calcium phosphate or oxid, in 

 definite proportions can not be reconciled with these facts. 



"The reaction between milk constituents, acids, etc.. in solution is reversible 

 and the state of equilibrium among the dissolved substances is affected by 

 changes of temperatures. 



" It is easy to correlate all the known facts respecting the curdling of milk, 

 if one accepts the view that chemical attractions hold all of the constituents of 

 milk serum iu union with each other. 



" Expressed in terms of this theory, milk curdles whenever the chemical at- 

 tractions of cui-d constituents for each other and of the whey constituents for 

 each other become relatively stronger than those which bind curd constituents 

 and whey constituents together." 



In brief, in the author's opinion the theory that there exists in milk a definite 

 compound of casein with calcium oxid or calcium phosphate, or any other single 

 milk constituent is untenable, and the theory that coagulation depends on the 

 removal of calcium oxid from a definite compound of casein naturally present 

 in milk can not be maintained. 



The coagulation of fresh and alkaline milks, J. L. Sajimis {Wisconsin Sta. 

 Rpt. 1907. pp. 190-206, figs. 12). — The data reported present "typical results 

 showing the effect of neutral salts on the coagulation of sweet fresh milk and 

 milk containing caustic alkali." These results resembled those obtained in the 

 previous study with acidulated milk (see preceding abstract). The facts ob- 

 tained confirm the conclusions there drawn, and " render it very certain that 

 milk curdling does not depend upon the neutralization of lime alone but is a 

 reaction in which all of the constituents of milk take part." 



