343 
the teat, ancl hence is a product of the milk gland itself, and not 
formed by the action of milk stagnated in the gland. Attempts 
to isolate this ferment from cow’s milk by Moro (5) and by Yan 
der Yelde and Landtsheer (7) have not proven successful. That a 
diastatic ferment does not occur in cow’s milk has also been con- 
firmed by Kastle. At present nothing definite is known regarding 
the function of this enzyme in human milk, and so far as we know 
it is not responsible for any alteration in the composition of any con- 
stituent of the milk itself. 
Galactase . — This proteolytic ferment was first recognized by Bab- 
cock and Bussell (8) 'in 1897, and has been found by these observers 
in the milk of the cow, woman, sheep, goat, pig, horse, and half- 
breed buffalo. By the methods ordinarily employed in the prepara- 
tion of enzymes, these authors succeeded in preparing from the fresh 
centrifuge slime of milk that had been kept continuously in contact 
with chemical antiseptics aqueous extracts possessing proteolytic 
properties to a marked degree. These extracts were also observed 
to have the power of curdling fresh milk, similarly to rennin, and 
also of rapidly decomposing hydrogen peroxide. Galactase has been 
found to be similar to trypsin in its action on proteids, converting 
them into proteoses and peptones and finally into amino-acids. Like 
trypsin it has been found to be most active in solutions that are 
slightly alkaline to litmus, and like all ferments it is easily destroyed 
by heat. 
Some idea of the changes produced in milk by the action of this 
enzj^me may be formed from the results of analyses made by Bab- 
cock and Bussell of milks that were allowed to stand for various 
intervals of time in the presence of an antiseptic to prevent the 
growth of bacteria. These results are given in the following table: 
Description of milk. 
Per cent of 
proteids in 
soluble 
form. 
Average of fresh whole milks analyzed 
21.07 
Average of whole milks, 20-25 days old 
Average of centrifugal skim milks (fresh) 
Average of centrifugal skim milks, 8-12 months old. 
Maximum found in skim milk 
38.27 
25.26 
73. 30 
91.18 
The proof of the enzymic nature of these changes is shown by the 
stability of milk heated to a sufficiently high temperature to destroy 
such ferments, and by the fact that fresh milks when preserved with 
powerful antiseptics, such as mercuric chloride, formalin, etc., un- 
dergo no change even though they be kept for indefinite periods of 
time. 
