324 
amounts of total solids and fat which they contained. His results 
are as follows: 
Total 
solids. 1 
Fat. 
(a) 
7.71 
0.868 
(6) 
6.80 ; 
. 633 
(e) 
W 
8.23 
.416 
Out of another lot of 103 samples analyzed by this chemist (47), 
the poorest milk had a specific gravity of 1.0275 and contained 9.04 
per cent total solids and 1.60 per cent of fat. 
The composition and also the yield of milk have been found to 
vary with the seasons of the year, with the character of the food, 
with the condition of the animal, and also whether it is fatigued or 
at work or at rest. It is also subject to some diurnal variation 
(Richmond (48)). It is also influenced by the addition of certain 
stimulants and nitrogenous compounds to the food. It also varies 
in composition during the course of lactation and also at different 
stages of the same milking. Sherman (49) has shown by monthly 
analyses extending over two years on a herd of 600 cows that the 
per cent of proteids in milk and likewise the fat varies with the 
season, being higher in autumn and winter than in the spring or 
summer. On the other hand the percentage of lactose remains prac- 
tically constant throughout the year. Richmond (50) also found 
the lowest percentage of fat in May and June and the highest during 
the winter months. On the other hand he found that the geology 
of the region over which the herd grazed exerted but little influence 
on the composition of the milk. 
Concerning the effect of food on the composition of milk, there 
seems to be a good deal of difference of opinion among different in- 
vestigators, some holding that the character of the food exerts a 
great influence on the character of the milk, others maintaining that 
this influence is but slight if any. According to Albert and 
Maercker (51) rations rich in fat cause a decided increase in the fat 
of the milk. If this however be continued for long intervals the 
fat falls to its original amount with the poorer rations. Rhodin (52) 
found that emulsified oils cause an increase in the amount of fat, 
followed by a return to the normal amount. These observations 
were confirmed by Bartlet (53). 
Gogitidse (54) found that by feeding sheep with linseed oil the fat 
of the milk could be made to contain as much as 33 per cent of lin- 
seed fat. Hills (55) observed that the addition of cotton seed, maize, 
or linseed oils to the food of cattle tends to increase the yield of milk 
per unit of dry matter fed. With cotton-seed oil there seemed to be a 
