METHODS OF EXAMINING MILK 285 
not properly cooled and cared for. When tested in this 
manner, milk will curdle before a sour taste is apparent 
and several hours before it will curdle spontaneously. If 
boric acid has been added to the milk as a preservative 
this will increase the acidity and influence the test. Sali- 
cylic acid generally has no influence because it is not usu- 
ally added in sufficient quantity. 
Milk also curdles when boiled when there is an excess 
of albumin or globulin present. In normal milk, albumin 
and globulin are not present in sufficient amount to make 
curdling visible when the milk is boiled. The udder se- 
cretion from individual cows will curdle on boiling for 
two to four days after parturition. Boiling will also cur- 
dle milk from cows affected with inflammation of the 
udder, cowpox, and nymphomania. During cestrum the 
milk sometimes curdles when boiled. It is necessary to 
test the milk of the individual cow to obtain a positive 
reaction in these cases. If the milk from the affected cow 
is mixed with the milk from other cows in the herd, the 
albumin or globulin may be so diluted that curdling will 
not be apparent. 
ALCOHOL TEST 
In applying the alcohol test, exactly equal quantities 
by volume of milk and 68 per cent. alcohol are mixed to- 
gether, after which the mixture is examined for flakes or 
curds. The flakes may be quite small and must be looked 
for carefully. The test is most conveniently made with 
a test tube marked for 5 ¢.c. and 10 ¢.c. The tube is filled 
to the 5 c.c. mark with 68 per cent. alcohol, and to the 10 
c.c. mark with milk, and the two fluids are then mixed 
by shaking. Milk should not be tested when cold, be- 
cause at low temperatures casein has a tendency to clump 
and form flakes. The flakes of fat formed when milk is 
