321 
when it was fed in conjunction with other foods deficient in fat. 
Pfeiffer, Ehfecke, and Schneider (64) have shown that asparagin 
when substituted for proteids, along with cane sugar, caused no dimi- 
nution in the yield of milk* in fact in some instances it seemed to 
cause an increase, but the amount and percentage of fat in milk was 
diminished. The feeding of this compound also acted unfavorably 
on the increase in live weight, and caused a reduction in the percent- 
age of proteids and dry matter in the milk. Morgen, Beger, and 
Westhauser (65) have reached the conclusion that amino compounds 
can not take the place of proteids in milk production, but that they 
exert a greater effect than carbohydrates. 
It has been observed that the actual yield of milk diminishes in 
the later period of lactation. According to Trunz (66), however, 
the specific gravity of the milk, and most of the solids, including the 
proteids, are relatively increased, while the proportion of albumin 
to casein remains remarkably constant throughout the entire period 
of lactation. This same investigator (67) has also made an exhaust- 
ive study of the mineral constituents of cow’s milk and their varia- 
tion during the period of lactation with the result that he has found 
considerable variation in the ash contents during the lactation 
period and that the total quantity of ash varies from time to time 
throughout the period, being as a rule less during the spring and 
summer months than during the autumn and winter months. 
Hardy (68) claims to have shown that the milk of a given cow 
varies in composition at the different stages of milking. Thus 
taking the milk in quantities of one-half liter at a time the milk of 
one cow gave the following successive numbers for fat: 2.2, 2.9, 3.5, 
3.75, 3.8, 3.9, and 4.65 per cent. 
The solids rose from 10.52 to 12.70 and the ash from 0.74 to 0.75 
per cent. The composition of the milk serum was found to remain 
the same throughout the milking. On the other hand Ackermann 
(69) claims that the conclusion that the fat increases in milk regularly 
during the process of milking, as this is ordinarily carried out, is 
incorrect. He has found, however, that by milking the teats singly 
or in pairs the fat did show an increase up to a maximum at the 
end of the milking and that on drawing the milk from the second 
pair of teats the quantity of fat was slightly more at the commence- 
ment than that given by the first pair and rose at the end of the 
milking to a higher maximum. The increase is probably due to a 
mechanical or physiological stimulus. 
The effect of work and fatigue on the quantity and quality of the 
milk has also been studied by several observers. Hill’s (70) results 
would seem to show that there is a slight falling off in the quantity 
of milk produced as a result of fatigue, 122.5 pounds against 131.4 
24907— Bull. 41—08 21 
