GG1 
The second effect excessive fat has in promoting gastro-intestinal 
disturbances lies in its behavior when casein is curded by rennet in the 
stomach. It is well known, among cheese makers, at least, that casein, 
when coagulated by rennet, carries down with it a very large per 
cent of the butter fat present. This is well shown in the case of the 
' cream cheeses, some of which contain nearly six times as much fat in 
their composition as casein. As the whey from whole milk contains 
no casein and less than 1 per cent of fat, it is obvious that the casein 
when curded brought down with it some 75 per cent or more, accord- 
ing to the richness of the milk, of all the butter fat originally present 
in the milk. The practical bearing this has upon the digestibility of 
cow’s milk proteid is as follows: The richer the milk in fat, the 
greater percentage of fat will then be in the curd formed by the gas- 
tric digestion. 
A very simple experiment will show in what way the digestibility 
of a rich whole milk would thereby be affected. Place a small por- 
tion of skimmed milk in a small flask with a narrow neck. In an- 
other flask place a similar portion of a rich milk containing say 5 
or 5.25 per cent, of fat. Add a small portion of liquid rennet to each, 
cork, and turn them slowly over and over in order to simulate peri- 
staltic action. In the case of the skimmed milk, as curding takes 
place, we see the formation of a flocculent curd, each particle of 
which remains separate. In the case of the milk rich in fat, the curds 
are dense and heavy, and show a remarkable tendency to coalesce and 
stick together. This is well brought out by attempting to pour out 
the curded milk from each bottle. Now, the curded skimmed milk 
pours out very easily, and, on examination, the curds are distributed 
throughout the whey in light flocculent masses,, while in the case of 
the milk rich in fat, pouring out will frequently be interrupted by 
large lumpy curds sticking in the narrow neck. Agitation of the bot- 
tle to break them up merely seems to increase their adhesive powers, 
each lump receiving further accretions from the particles floating in 
the neighborhood. 
W e can easily, then, predict the events that take place when a milk 
rich in fat is acted upon by the gastric juices in the infant’s stomach. 
In fact, this action of fat in making curds, large and indigestible by 
reason of their excessive fat content, has long been known to dairy- 
men, as they are well aware of the fact that Jersey cows often can not 
nurse their calves by reason of the excessive richness of their milk. 
And yet one would never for one moment suppose, under normal cir- 
cumstances, that the casein of cow’s milk is ever indigestible per se to 
the calves for which it is intended. 
In the case of the human infant, if the milk be too rich it is vom- 
ited. If it is just rich enough to produce a curd with a fat content 
greater than it should have, peristalsis is checked and the stomach 
