616 EXPERIMENT STATION RECORD. [VoL 41 



simultaneously from the right and left breasts, and of the variations in com- 

 position of milk taken at three-hour periods during the course of a single day. 

 Lactose was determined by the titration method of FoUn and Denis (E. S. R., 

 38, p. 615), fat by the Babcock method or, when the amount of material was 

 limited, by Bloor's nephelometric method (E. S. R., 32, p. 312), and protein 

 by the Kjeldahl method. The detailed results are presented in tabular form. 



There was found to be a rapid increase in lactose during the first few days 

 and a further increase as lactation progressed. This was accompanied by a 

 corresponding decrease in protein. After the colostrum period there was ap- 

 parently no relation between the stage of lactation and the amount of fat in the 

 milk. The percentage of lactose was usually higher, and fat lower, at the be- 

 ginning of a single nursing than at the end. There was little if any difference 

 in the protein. The milk taken simultaneously from both breasts of the same 

 woman tended to have the same composition, but often varied in the percentage 

 of fat. The percentage of fat was as a rule higher at midday or midafternoon 

 than at other times during the day. 



The results emphasize the importance In the analysis of human milk of ob- 

 taining samples both before and after nursing. Instead of making the analysis 

 on the first ounce of milk drawn. 



The nonprotein nitrogenous constituents of cow's milk, W. Denis and A. S. 

 MiNOT {Jour. Biol. Chem., S8 (1919), No. S, pp. 45S-458). — Figures are given for 

 the nonprotein nitrogen, amino nitrogen, urea, uric acid, creatinin, and creatm 

 in cow's milk as determined by the methods previously described (B. S. R., 

 40, p. 509). Determinations were made on the mixed product of 4 large milk 

 distributing plants, on 38 samples of milk from Individual cows In 3 dairies, on 

 milk obtained from 7 cows fed rations of known composition, and on milk ob- 

 tained from a single cow during the first 4 weeks after calving. 



While different samples of mixed milk of a large number of cows gave prac- 

 tically uniform results, the milk taken from Individual cows in different 

 dairies showed noticeable differences in the values for nonprotein nitrogen and 

 urea. The content of nonprotein nitrogen, amino nitrogen, and urea was found 

 to be influenced by the character of the food, being increased in high protein and 

 decreased in low protein feeding. The content of these same constituents was 

 found to be high in colostrum, and to approach normal values only on the 

 fourth day after delivery. 



Peroxidases in milk, H. Violle (Coinpt. Rend. Acad. Sci. [Paris], 169 (1919), 

 No. 5, pp. 248-250). — The freshly cut mammary glands of guinea pigs, washed 

 free from blood and milk, were found to react positively to the guaiacum 

 peroxidase test, although the milk exuding from such glands gave a negative 

 test. This is thought to indicate that normal fresh milk may contain only 

 traces of oxidizing diastases, while milk from diseased glands is likely to con- 

 tain larger amounts. It is further pointed out that although heating to 78 or 

 80° C. destroys peroxidases, heated milk may be easily adulterated by the 

 addition of peroxldase-containing substances. The author therefore concludes 

 that the quality of milk can not be judged by the peroxidase reaction. 



Concentration of ammonia in blood. — Comparison with concentration of 

 ammonia in different secretions and tissues, especially muscle tissue, K. L. 

 Gad-Andersen (Jour. Biol. Chem., 39 (1919), No. 2, pp. 267-271).— A method of 

 estimating ammonia and urea in muscle is outlined by moans of which the 

 transformation of urea into ammonia after death Is thought to be prevented. 

 This is brought about by stunning the animal on the back of the head, excising 

 the muscle as quickly as possible, and keeping it under alcohol at a temperature 

 of —20" C. until the determinations are made. Ammonia Is estimated by aera- 

 tion and urea by the urease method. 



