350 
ate, which, like the salts of other weak acids, is readily hydrolyzable, 
yielding a certain amount of free base, namely, calcium hydroxide, 
and partly on the insoluble phosphates. In the case of milk the 
alkalinity toward lacmoid depends on these two factors and also on 
the presence of diphosphates. The greater alkalinity of cow’s milk 
depends partly on the larger quantity of insoluble phosphates pres- 
ent, but principally on the presence of diphosphates. As has been 
repeatedly shown, human milk is more alkaline than cow’s milk. 
According to Courant, however, it, like cow’s milk, is also acid to 
phenolphthalein and alkaline to lacmoid. In the case of cow’s milk 
he found the ratio of alkalinity to acidity to be y -^-= = 2.1, and in the 
1.95 ’ 
case of woman’s milk 
1.08 
0736 ~ 3 ' 
According to this author the rela- 
tively slight acidity of woman’s milk is due to the small quantity of 
caseinogen which it contains and also in all probability to the fact 
that it contains its caseinogen in the form of tricalcium caseinogenate. 
To return for a moment to the subject of the rennin coagulation of 
milk, it would seem that certain aspects of this change exhibit an 
analogy to the action of a toxin. It has been shown, for example, 
by Hammarsten and Roden (43) that normal horse serum contains 
a substance capable of inhibiting the action of rennin. In other 
words, it contains an antirennin. Similarly, by repeated injection 
of small amounts of rennin into the blood of animals, Morgenroth 
(44) obtained an antirennin. According to Fuld and Spiro (45) the 
antirennin of normal horse serum prevents the coagulation of milk by 
binding the calcium ions. Arrhenius is therefore of the opinion that 
in these reactions rennin corresponds to the toxopliorous group, the 
calcium ions to the haptophorous group of a toxin, and the antirennin 
to an antitoxin. 
Many additional facts concerning the rennin ferment are known. 
Like other ferments it is affected by he£t, and the rate of the remiin 
coagulation is determined both by the quantity of rennin acting and 
by the temperature, sit has been shown that the ferment can with- 
stand a temperature of — 180° C. without injury. At temperatures 
higher than 44° C. the ferment gradually loses its activity, and expo- 
sure to a temperature of 50° to 60° C. for a considerable time has been 
found to be more harmful than a short exposure to a higher tempera- 
ture. The effect of temperature is also determined by conditions sur- 
rounding the ferment, whether it is moist or dry, and also by The 
reaction of the solution containing the ferment. In the dry state it 
can withstand a temperature of 100° to 140° C. Its destruction by 
heat has been found to follow the law for a monomolecular reaction. 
