327 
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 (71) have reached the conclusion that amino compounds 
{ can not take the place of proteids in milk production, but that they 
I 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 (72), 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 (73) has also made an exhaust- 
ive study of the mineral constituents of cow’s milk and their varia- 
!j 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 
i summer months than during the autumn and winter months. 
:i Hardy (74) claims to have shown that the milk of a given cow 
I varies in composition at the different stages of milking. Thus 
I taking the milk in quantities of one-half liter at a time the milk of 
1 one cow gave the following successive numbers for fat: 2.2, 2.9, 3.5, 
I 3.75, 3.8, and 4.65 per cent. The solids rose from 10.52 to 12.70 
I and the ash from 0.74 to 0.75 per cent. The composition of the milk 
i serum was found to remain the same throughout the milking. 
On the other hand Ackermann (75) claims that the conclusion that 
j the fat in milk increases regularly during the process of milking, as 
1 this is ordinarily carried out, is incorrect. He has found, however, 
I that by milking the teats singty or in pairs the fat did show an in- 
crease up to a maximum at the end of the milking and that on draw- 
ing the milk from the second pair of teats the quantity of fat was 
slightly more at the commencement than that given by the first pair 
and rose at the end of the milking to a higher maximum. The in- 
crease 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. Hills’s (76) 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 
pounds after rest. The total solids and the fat were found to be 
slightly higher during the period of fatigue than after rest. Domic 
(77) also has shown that the yield of milk is diminished slightly as 
the result of work. The dry matter and the amount of acid were 
