476 



VICTOR C. MYERS 



eighteen patients on admission averaged 0.0035 per cent., while on dis- 

 charge it was 0.0047 per cent. 



Milk 



Milk is a product of the secretory activity of the mammary gland. 

 It is the most satisfactory food material elaborated by nature. As a food 

 it is deficient in only one respect, viz., its iron content. This is without 

 significance when milk is used as a food for infants, since a considerable 

 quantity of iron is stored up in the liver during fetal life. Milk contains 

 the proteins, casein and lactalbumin, such fats as olein, palmitin, stearin 

 and butyrin, the disaccharid, lactose, together with phosphates of calcium, 

 potassium and magnesium, citrates of sodium and potassium, and chlorid 

 of calcium. In addition it is evident from recent observations that milk 

 is well supplied with the water soluble and fat soluble vitamins, to- 

 gether with a sufficient quantity of the antiscorbutic element. 



The physical appearance of milk suggests that the various constituents 

 are not all in solution. Fat is present in a finely divided suspension, 

 while casein is either in suspension or in a colloidal solution. Van Slyke 

 and Bos worth have been able to separate the insoluble portion of milk 

 by filtration through a Pasteur-Chamberland filter. With the aid of this 

 method they have been able to divide the constituents of milk into three 

 groups as shown by the table below: 



MILK CONSTITUENTS 



Perfectly fresh milk, both human and cow's, is amphoteric in reac- 

 tion toward litmus and acid to phenolphthalein. The acidity to phenol- 

 phthalein is due in considerable part to acid phosphates, although acid 

 caseinates may be responsible for some of the acidity. The specific gravity 

 of milk most often varies between 1.028 and 1.032. Milk has a very 

 slight yellow color, which is more noticeable in the cream on standing. 

 The yellow pigments of butter fat are the vegetable pigments carotin and 

 xanthophylls. They are present in the colostrum in mjich higher con- 

 centration than in mature milk. 



The milk of different species of animals differs very materially, the 

 animals with a rapid rate of growth secreting a milk with a much higher 



