THE GENERAL NATURE OF DIET 157 



more or less with the debris of this activity. Besides this, the so-called 

 "colostrum-corpuscles" may be seen under the microscope; these con- 

 sist of modified leukocytes or perhaps of milk-cells, with the butter- 

 droplets to be seen within them. Perfect leukocytes also are sometimes 

 found. The chemical composition is different from that of the milk 

 coming later, colostrum containing much more lactalbumin and more of 

 a material often described as a globulin, the " lactoprotein" or lacto- 

 globulin mentioned above. The colostrum is said to act as a purgative 

 partly in the newborn child, cleansing and preparing the intestinal 

 mucosa for its work. 



The coagulation of milk (very like that of blood), commonly called 

 "curdling," consists in the formation of a clot composed of casein entang- 

 ling much of the fat. In the presence of salts of calcium, the enzyme 

 rennin acts on the caseinogen in solution in the milk-plasma, splitting 

 it into two parts, one, soluble in the plasma, called whey-pro teid, the 

 other caseinogen, which is insoluble. This is a process of hydrolysis, and 

 occurs only in the presence of calcium phosphate. This substance, 

 casein, with its included fat constitutes the curd. The caseinogen in 

 solution in the whole milk seems to be a combination of a nucleoproteid 

 (nuclein) and a somewhat globulin-like proteid. This is the present 

 most-accepted theory of the coagulation of milk, but not yet proved;, 

 compare the coagulation of blood. 



The coagulating enzyme, rennin, is secreted by the glands of the stom- 

 ach and of the pancreas. For the manufacture of cheese an impure 

 briny infusion called rennet has long been in use, made from the fourth 

 stomach of the calf. One part of rennet will coagulate nearly 1,000,000 

 parts of caseinogen. 



The souring of milk consists of the acid-fermentation of its lactose 

 from the influence of special bacilli which are present everywhere in the 

 air and in the large intestine. The lactose, absorbing water, becomes 

 lactic acid, which then breaks up into butyric acid, carbon dioxide, and 

 hydrogen. This acid is very apt to injure the digestive process, if not 

 the digestive organs, of young children. Hence the harm from sour or 

 souring milk. The latter, being in a state of active bacterial change, is 

 worse than the former. 



It appears that the hydrolyzing enzymes of the alimentary canal, the 

 digestive "ferments," as they used to be called, do not develop in the 

 infant all at once, nor are they all actively strong in the child less than 

 seven months old. After that period the use of some solid food is properly 

 begun, although milk should form a considerable part of the aliment of 

 the child the first five years at least. No solid nutrients are better adapted 

 to early use in the first year than lightly boiled eggs and buttered stale 

 wheat bread. The yolk of the eggs is especially valuable, as it contains 

 much iron, and also fat and proteid in a combination perfectly adapted 

 to the child's first year or two. Gradually the list of common articles of 

 diet is enlarged, great stress being laid upon easily digested proteids and 

 on ripe, juicy, fresh fruits and well-cooked fresh vegetables. These 



