578 EXPERIMENT STATION RECORD. [Vol.43 



An economic method of determining the average percentage of fat in a 

 cow's mill£ for a lactation period, E. J. Shkehy {Sci. Proc. Roy. Dublin Soc, 

 n. ser., 15 (1919), No. 40, pp. 5.',6-513, pi. 1, figs. 6).— The author tabulates the 

 Individual moniiug and evening milk yields and fat percentages of 11 cows for 

 40 consecutive days and similar daily data for one cow during nearly 9 months, 

 the object being, to find a method of estimating the fat yield of a lactation fi-om 

 systematic weighings of milk and a limited number of fat analyses. It is con- 

 cluded that analyses on 4 successive days during the nriddle of lactation (par- 

 ticularly the fifth and sixth months) provide an average fat percentage which 

 in genei-al differs from the true lactation average by less than 10 per cent. 

 Samples for analysis are not to be collected within several weeks of change 

 to or from pasture. 



The comparative variation of the constituent substances of cows' milk, 

 E. J. Sheehy {Sci. Proc. Roy. Duhlin Soc, n. ser., 15 {1919), No. 41, pp. 574- 

 584, flos- 4)- — The author tabulates the morning and evening milk and fat 

 yields of a cow during 82 consecutive days and the fat percentage and lactom- 

 eter reading of each milking, and by Richmond's formula estimates the total 

 solids, solids-not-fat, and water content of each sample. From inspection of 

 these data in tabular and graphical form it is concluded that the fat is the 

 most variable conslituent. 



"A lactating cow produces water and solids-not-fat in proportions which are 

 practically constant and produces fat in proportions which bear no constant 

 ratio to the total milk, thus indicating that fat production is influenced by 

 factors which are not identical with those influencing the production of the 

 other constituents of the milk." 



Conditions causing variation in the reaction of freshly drawn milk, L. L. 

 Van Slyke and J. C. Baker iNew York State Sta. Tech. Bui. 70 {1919), pp. 

 9; also in Jour. Biol. Chem., 40 {1919), No. 2, pp. 345-355).— In 308 samples of 

 cow's milk, each representing the foremilk from one quarter of the udder, the 

 H-ion concentration varied from pH=6.5 to pH^7.2. In 83 per cent of the 

 samples pH was less than 6.7G. In two sets of samples, collected from the 

 separate teats of 20 cows, some erratic variations in the reaction of milk from 

 the different quarters of the udder of the same cow were observed. In the 

 first set the 4 samples were approximately uniform in the case of 4 animals, 

 and in the second set (not presented in detail) they were uniform in 10 

 invididuals. In one case milk from the right front quarter belonged in the 

 most acid group of samples, while that from the right hind quarter was the 

 only definitely alkaline sample of the 80 tested. 



Chemical analyses were made of 15 samples of known pH values, and leucocyte 

 and streptococcus counts were made of the 10 having the lowest H-ion con- 

 centration. In general, with a decrease of acidity there was a definite 

 tendency toward a decrease in specific gravity and in the percentages of fat, 

 total solids, soli ds-not- fat, casein, and sugar; and an increase in noncasein 

 protein, ash, and chlorin. The samples of high leucocyte content were 

 alkaline except where acid-producing streptococci wei-e present. 



Because of this relationship between leucocytes and low acidity, which was 

 confirmed by observations on milk known to have been derived from diseased 

 udders, the hypothesis was formulated that the lowered acidity resulted from 

 the direct passage of blood serum iiito the alveoli through lesions caused by 

 bacterial action. However, careful tests for glucose in the milk serum were 

 negative, and it is concluded that at least the blood sugars underwent trans- 

 formation in the udder. 



Reaction of milk in relation to the presence of blood cells and of 

 specific bacterial infections of the udder, J. C. Baker and R. S. Breed 



