chemical combination or as an intimate mixture. In this connection 
it has been shown by Harris (34) that in the curdling of milk by 
rennin 13 per cent more calcium phosphate is used up than in the 
acid coagulation of milk. 
In this connection Courant's (IT) Hews regarding the composition 
of milk and the manner in which the caseinogen is held therein afford 
the most satisfactory explanation of the conduct of fresh milk toward 
chemical indicators. To review this subject briefly, Courant has 
found that cow’s milk and caseinogen solutions, such as that whose 
composition is given in the above equation, react alkaline to lacmoid 
and acid to phenolphthalein. The acidity of fresh cow’s milk proved 
to be slightly less than that of the caseinogen solutions ; the alkalin- 
ity of milk, on the other hand, was nearly twice that of the caseinogen 
solutions. He reaches the conclusion that one half of the acidity 
toward phenolphthalein as shown by cow’s milk and his caseinogen 
solutions is due to the acidity of dicalcium caseinogenate, and the 
other half to monophosphates. In this calculation he purposely neg- 
lects the slight acidity of milk due to the free carbonic acid which 
it contains. The alkaline reaction toward lacmoid depends in the 
case of the caseinogen solutions partly on the dicalcium caseinogen- 
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 aciditv to be 2.1. and in the . 
1.9o 
1 08 
case of woman’s milk ^Ty:=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 (35) 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 
