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 oestrum 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.c. and 10 c.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 



