THE ALCOHOL TEST IN RELATION TO MILK. 33 
alcohol test indicates some change in the milk from its normal con- 
dition. In our opinion the value of the alcohol test with milk from 
a single cow or small herd lies in the fact that it would show that the 
milk was abnormal, and in consequonce a careful examination should 
be made of the herd. 
When the relation of the alcohol test to mixed market milk is dis- 
cussed, we must consider it on an entirely different basis. In this 
case the test with 68 per cent alcohol may be positive as a result of 
changes produced in milk through bacterial action. The results of 
our work confirm some of the results of other investigators and show 
that the alcohol test may be positive as a result of the growth in milk 
of lactic-acid and rennet-forming bacteria. When the growth of 
these bacteria has reached a point where the acid or rennet is pro- 
duced in sufficient quantities to affect the casein, a coagulation is 
produced when equal volumes of 68 per cent alcohol and milk are 
mixed. Our results, however, do not show that there is any definite 
relation between the alcohol test and the number of bacteria in milk. 
During an examination of 177 samples of raw milk we found that 20 
samples gave a positive test with 68 per cent alcohol. Of these 20 
samples 8, or 42.1 per cent, contained less than 500,000, and 11, or 
57.9 per cent, more than 500,000 bacteria per cubic centimeter. It 
was also found that 39.4 per cent of 142 samples of milk which gave 
no positive alcohol tests contained over 500,000 bacteria per cubic 
centimeter. That there is no definite relation is probably explained 
by the fact that bacteria may increase in large numbers before there 
is much acid or rennet produced. Consequently, if an alcohol test 
were made during that period there would be a high bacterial content 
and yet not enough change produced in the milk by acid or rennet 
to cause a positive test. Besides this point it must be remembered 
that in market milk there is a bacterial flora representing many dif- 
ferent species, many of which may increase without influencing the 
alcohol test. 
As stated before, generally speaking, when the bacterial fermenta- 
tions have advanced to a point where chemical changes are produced, 
the alcohol test will be positive as a result of lactic or rennet fermen- 
tations, or a mixture of both. In such cases the alizarol test may 
be of more value than the plain alcohol test, so far as it may give 
additional information as to the kind of fermentation. From our 
results it seems evident that the acid-and-rennet fermentations may 
be differentiated by means of neutralization of the acidity by sodium 
hydrate. 
The alcohol titration method according to our tests seems to offer 
no particular advantages over the alcohol test. In a study of 116 
samples we were not able to find any definite relation between the 
alcohol titration and the bacterial count. 
