Average herd milk of good quality. 
Per cent. 
Fat 4. 00 
Proteids 3. 50 
Salts . 75 
Sugar 4.50 
Water 87. 25 
100. 00 
Caloric value per kilogram, 700 calories. 
Physical characteristics of cow’s milk. Its color is white, varying 
from a clear to a yellowish white. It is very opaque, the opacity 
being due to its large content of calcium in combination with its 
casein. Its specific gravity varies from 1.028 to 1.033 with an aver- 
age of 1.031. Its taste is pleasant and charateristic. The addition of 
acetic acid causes a flocculent precipitate, and on the addition of 
rennet it coagulates into a firm mass. 
Reaction . — When freshly drawn this is amphoteric or slightly 
alkaline ; on standing it soon becomes acid. 
Proteids . — The proteids of cow’s milk consist mostly of casein in 
combination with calcium. As in woman’s milk, lactalbumen is 
also present but in small quanity. According to Koenig, casein is 
present in the proportion of 7 to 1 as compared to lactalbumen. 
Fat . — The fat in cow’s milk is the element that is most subject to 
variation, as the content of the other food elements is remarkably 
constant. A milk poor in butter fat contains about 3 per cent, while 
a rich milk, such as milk from Jersey cows, contains 5 to 5.25 per 
cent of fat. It is highly important to know the percentage of fat 
present in milk actually being used for the feeding of infants for 
reasons discussed later on. 
The sugar of cow’s milk is practically identical with that of 
woman’s milk, and is present in the proportion of about 4.50 per 
cent. 
Salts . — Inorganic salts are present in the proportion of 0.75 per 
cent, of which calcium and phosphoric acid are the most abundant 
constituents. 
Bacteria. — Cow’s milk always contains a large number of bacteria, 
their number increasing with the age of the milk and the conditions 
under which it is kept. 
Cream . — Cream is merely cow’s milk rich in fat to excess. It is 
obtained either by skimming the milk (gravity cream) or is separated 
from it centrifugally by a machine known as a separator. It differs 
from milk but slightly in its other solids. Very rich cream (40 pfcr 
cent) contains relatively less sugar and proteid (sugar 3 per cent, 
proteid 2.20 per cent). The usual strengths of separated creams 
