milk serum} The fat is suspended in the milk in microscopic glob- 

 ules, which are semi-solid, and with the serum, form what is termed 

 an emulsion. 



Milk fat. The fat globules in milk are exceedingly minute (from 

 .0016 of a millimeter to .01 of a millimeter in diameter). The glob- 

 ules in the milk produced by Jersey and Guernsey cows are larger 

 in size than those produced by Holsteins or Ayrshires. The glob- 

 ules are largest in the milk of new milch cows, and the cream from 

 such milk separates quickly. The percentage of fat in pure milk 

 varies between 2.25 and 8 per cent., with an average of about 4 per 

 cent. Cream may be defined as that portion of milk into which a 

 large part of its fat has been gathered. Cream contains from 15 to 

 50 per cent, of fat, depending upon the method of separation. 



Milk albuminoids (nitrogenous matter). Casein, which forms 

 some 85 per cent, of the total albuminoids, exists in milk combined 

 with lime in a semi-dissolved condition, and possesses a certain de- 

 gree of opacity (lack of transparency). It forms with the fat the 

 chief ingredients of milk curd, and of full cream cheese. 



Albumen differs from casein in being completely dissolved in milk, 

 and in separating from the serum when milk is heated to from 158° 

 to 167°. Lactoglobulin, mucoid protein and fibrin are other nitro- 

 genous substances which exist in milk in small quantities. 



Milk albuminoids represent that part of the milk which forms 

 flesh in the growing animal or human being. 



Milk sugar, recognized late in the seventeenth century, is found only 

 in milk, where it exists in a state of perfect solution. It is not as 

 easily soluble in water as cane sugar, and possesses only a slightly 

 sweetish taste. The quantity in normal cows' milk varies from 3 to 

 6 per cent., with a probable average of 4.80 per cent. The sugar 

 can be separated from the milk, and brought into a solid form, re- 

 sembling powdered white sugar. It is used more or less by drug- 

 gists and in infant food preparations. The commercial demand for 

 it is limited, and does not warrant its manufacture in large quantities. 



Milk ash consists of potash, soda, lime, magnesia and iron, com- 

 bined with phosphoric, hydrochloric and sulfuric acids. The potash, 

 lime and phosphoric acid form the largest portion of the ash, 



' That portion of the casein which can be removed by filtration through filter paper, is 

 not generally included in normal serum. 



