702 
stants not affecting its specific gravity, and estimating the proteids 
from our knowledge of the fat content of the specimen. Now, the 
specific gravity will vary directly with the proteids and inversely to 
the fat, viz, high proteids, high specific gravity; high fat, low spe- 
cific gravity. The following table shows the application of this 
principle : 
Variations in the composition of ivoman's milk as deduced by observation of 
the specific gravity and the fat content (Holt). 
Specific gravity, 70° F. 
Cream, 24 hours. 
Proteids, estimated. 
Average 
1,031 
7 per cent 
1.50 per cent. 
Normal (rich milk). 
Normal (fair milk). 
Normal or slightly 
below. 
Low (very poor milk) . 
Very high (very rich 
milk). 
Normal or nearly so. 
Normal variations 
Normal variations 
1,028-1,032 
1,031 
8-12 per cent 
5-6 per cent 
Abnormal variations 
Abnormal variations 
Abnormal variations 
Abnormal variations 
Low (below 1,028) 
Low (below 1,028) 
High (above 1,032 ) . . . 
High (above 1,032) 
High (above 10 per cent) . 
Low (below 5 per cent) . . 
High 
Low 
As the milk drawn from the breast during the first part of nursing 
is richer in proteids and much poorer in fats and the last portion 
rather poorer in proteids and rich in fats, the entire amount of milk 
present in the breast should be drawn off for the purpose of this esti- 
mation. 
. cow’s MILK. 
Cow’s milk is the only food supply, apart from mother’s milk, 
available in this country, from a practical standpoint, for the nourish- 
ment of infants under 1 year of age. It forms besides a large part of 
the dietary of older children and of many adults. It is consequently 
of the utmost importance, in view of its perishability, that it should 
only be used as a food under conditions which will insure its whole- 
someness. 
We have already considered the enormous loss of life occurring 
among the artificially fed infants, of which the larger part is un- 
doubtedly due to bad milk and its improper use as an article of diet. 
Stated as a general proposition, the following conditions should be 
fulfilled in milk that is to be used as a basis for the nourishment of 
young infants: First, it should be clean; second, it should be fresh; 
third, it should be whole (i. e., not falsified by additions or subtrac- 
tions of its component parts or by the addition of preservatives) ; 
fourth, it should be free from pathogenic organisms and toxic prod- 
ucts ; and fifth, it should be kept cold. 
Importance of clean milk. — By" clean milk we understand a milk 
which has been collected under such hygienic conditions from healthy 
