Specific Gravity of Milk 19 
in four or five days after calving, the milk loses its 
colostrum character and.takes on its normal condi- 
tion. This change is a gradual and progressive one, 
and is more or less .dependent upon the physical 
condition of the animal. When the cow is feverish, 
or when there is local inflammation in the udder, 
the colostrum character of the milk is retained 
for a longer period than otherwise. The amount 
of coloring matter present is also considerably 
greater in colostrum than in normal milk, and the 
percentage of fat varies very widely. Usually the 
percentage of fat is less in the colostrum than in 
the normal milk from the same cow, although oc- 
casions are not infrequent where more fat is found 
in the milk immediately after calving than at any 
other time in the whole period of lactation. 
Specific gravity of milk.—Some of the solids of 
milk are heavier than water and some of them lighter, 
milk as a whole having a specific gravity somewhat 
greater than water. The variation in the specific 
gravity is considerable, the range usually given being 
from 1.029 to 1.085 at 60° F., the average being 
about 1.032. _In general, the effect of an increase 
in the solids of the milk is to increase its- specific 
gravity, though in milk extremely rich in fats (6 
per cent or above) the specific gravity is lessened. 
Formerly, more than at present, it was the custom 
to estimate the quality of the milk by determining 
its specific gravity, but as soon as it became known 
that the specific gravity depended not so much upon 
the amount as upon the character of the solids, a 
