respect adapted to the growing organism (Lit. 2, 3). The great point is, that the suckling is constantly supplied with the same mixture of salts and the same organic nourishment, namely, albumen, carbohydrates, and fats. Later, when mixed nourishment is taken, the conditions become much more complicated, according as greater quantities of this or that unit are introduced during digestion. The cells of the intestines are continually confronted with new duties, and have to adapt themselves gradually to the new conditions.
The cells of the milk glands are charged with the proper choice of food. They prepare the food for the developing organism, and simplify in particular the task of the intestines which, with the help of the liver, prepare the ingested food for the other cells of the body. Even the components of the milk, before they can be of any use to the organism, must be first considerably altered in the intestine, just as later, in the case of mixed food, a complete decomposition by means of the ferments precedes absorption. The difference in respect to the latter mode of nourishment only lies in the fact that, with the milk food, the same stages of decomposition, giving rise to the same by-products, always recur. Day after day, to a certain extent, the cells of the intestines and of the organism have to perform the same task.
From this point of view we may discern three
