GENERAL CHEMISTRY OF MILK 



RELATION OF FAT AMD CASEIN DURING THE LACTATION PERIOD 



119 



According to these figures, the casein decreases in somewhat 

 greater proportion than the fat, and toward the end of lactation 

 increases in greater proportion. 



Milk-sugar is less variable than either proteins or fat. This 

 is agreed to by all authorities. The amount of sugar is very con- 

 stant throughout the whole lactation period with the exception 

 of a slight decline toward the end. 



Total Solids. — The total sohds naturally follow the decrease 

 and increase of proteins and fat, modified only by the relative con- 

 stancy of the milk-sugar and ash. There is a dechne during the 

 first and sometimes during the second month, followed by little 

 change up to the eighth or ninth month, and finally a marked 

 increase. 



Oooo 



Fig. 26. — The decrease of the fat globules during the lactation period (Ecliles 



and Shaw). 



In the experiments of Eckles and Shaw the protein represented 

 27 per cent, of the total solids at the beginning of lactation, and 

 increased so that at the end 3 per cent, were added. Casein in- 

 creased slightly more than the total solids, while albumin increased 

 slightly less. The fat constituted 31.3 per cent, of the total solids 

 and increased 2 per cent, by the time the end of lactation was 

 reached. The milk-sugar averaged 37 per cent, of the total solids. 

 In the beginning it was 38.2 per cent, and at the end 32.8 per cent. 



The relative increase of sugar as compared with that of fat — 

 in the beginning of the lactation period — is only apparent, and is 

 due to the decrease of fat. The sugar remains nearly constant 

 except for a decline toward the close of lactation. 



The fat globules underwent a characteristic change during 



