12 DAIRY CHEMISTRY 



average is about 9 per cent. The greatest difference 

 in the composition of various milks is in the fat con- 

 tent. Any material increase in the total solid mat- 

 ter of milk is due mainly to an increase of the fat. 

 The solids not fat are subject to but slight varia- 

 tions compared with the fluctuations of the fat. 



Nearly all of the important fluids of the body, like 

 the blood, are normally quite constant in chemical 

 composition. With milk the constancy of composi- 

 tion is confined mainly to the serum solids, or solids 

 not fat. 



