GENERAL CHEMISTRY OF MILK 



115 



are, in general, in harmony with previous findings, and have added 

 a great deal of valuable evidence to facts already known. With 

 the exception of the ash content their work covers the quantita- 

 tive change in milk constituents during the lactation period in a 

 very thorough manner. The reports are given on milk examina- 

 tions covering four-week periods during the whole length of lac- 

 tation. The material was obtained from 1 1 cows belonging to four 

 different breeds, namely, Jerseys, Holsteins, Ayrshires, and Short- 

 horns. The following table, condensed from the author's detailed 

 reports, gives the total milk production and fat from the breeds 

 whose milk was examined: 



THE AMOUNT OF MILK AND FAT PRODUCED BY 3 JERSEYS, 3 HOLSTEINS, 2 AYRSHIRES, 

 AND 3 SHORTHORNS DURING A LACTATION PERIOD IN FOUR-WEEK PERIODS 



The figures show that at the commencement of the second 

 four-week period the quantity of milk from Holsteins and Ayr- 

 shires increased shghtly, and from that time on decreased gradually 

 for eight to ten periods, and rapidly toward the end of lactation. 

 The apparent increase in Jersey milk production from the twelfth 

 to the thirteenth period has no significance, as it is due to the 

 dropping out of two of the animals which were less productive 

 than the third one. This increased the figure, of course. The 

 milk from the other two breeds diminished steadily, but in giving 

 these figures in four-week periods an increase during the first 

 period may be observed. The amount of fat produced was in 

 proportion to the decrease of total milk-.supply. 



The detailed results of analyses of milk constituents during 

 the period of lactation have been tabulated by the authors in a 

 large number of elaborate tables from which the most important 

 figures are incorporated in the following summary: 



