350 REPORT OF THE CHEMIST OF THE 
(1) In dairy schools.—As a matter of general educational 
training in making a laboratory study of the composition of 
milk, a casein test has value, independent of its possible prac- 
tical applications. 
(2) In dairy nutrition investigations.— In many dairy in- 
vestigations of nutrition problems, it is desirable to know 
the percentage of casein in milk. This factor has frequently 
been omitted on account of the amount of work involved in 
determining casein by the “ official ” method. 
(3) In studies of composition of milk.— In chemical labora- 
tories, especially those connected with agricultural experiment 
stations, where systematic studies of the composition of milk 
are being made, the determination of casein is usually a neces- 
sity, if results of value are sought. 
(4) In municipal and state inspection laboratories.— The 
inspection of milk by municipal and state authorities has rarely 
taken casein into consideration in determining the normal 
character of milk. The relation of fat and casein can be made 
a desirable basis for ascertaining when fat has been removed 
from, or skim-milk added to, normal milk. 
(5) In the preparation of modified milk for infant feeding.— 
It is a common practice among physicians to modify cow’s 
milk on the basis of the relation of fat to casein for feeding 
infants. The general purpose is diminution of the ratio of 
casein to fat as it ordinarily exists in cow’s milk. The prepara- 
tion of modified cow’s milk for such purposes has usually been 
based on guess-work. The ability to determine easily the 
amount of casein, as well as fat, in cow’s milk gives physicians 
a control of the process which they have not previously had. 
(6) In cheese-factories.— The relation of casein and fat in 
milk is an important one in connection with cheese-making. 
There are times when the normal ratio is so disturbed as to 
call for modifications of the process of cheese-making or else 
serious loss of cheese yield is apt to be experienced. Thus, in 
times of severe drought, the casein usually decreases in relation 
to fat to such an extent as to result in large losses of fat, 
when the usual conditions of cheese-making are followed. 

