CHAPTER I 

 INTRODUCTION 



Milk consists of (i) fat in small globules (Fig. i) 

 ranging in size from o.oi mm. in diameter to 0.0016 ; 

 (2) milk-sugar and (3) various salts in solution in 

 wa'er ; (4) caicin, combined with lime and phos- 

 phoric a^id; and (5) albumin in loss perfect solution. 



i. Milk (magnified 400 diameters). 



There are in addition (6) other compounds in small 

 quantities, including enzymes or natural ferments. 



The fat will be treated of in the section on butter ; 

 the milk-sugar belongs to the class of carbo-hydrates 

 and crystallises with i OH 2 , and is one of the hexa- 

 bioses. It rotates the plane of polarisation, its specific 

 rotatory power being 52.5 for the crystallised sugar ; 

 and reduces solutions of copper salts. 



Casein is a protein belonging to the class of the 



I A 



