DEVELOPMENT G37 



lipins of the milk are much more abimclant than those in 

 the blood serum. 



The fat occurs in the form of minute globules. Coal- 

 escence is prevented by the surface tension of the spheres, 

 and by the adsorption of protein on the surface. It cannot 

 be separated from milk by ether till the globules are broken 

 down by an acid or an alkali. 



The specitic gravity of the fat is '93, while that of the 

 milk free from fat is about 1'035. The globules of fat, 

 therefore, tend to rise to the surface to form cream. The 

 mechanical agitation in churning causes the globules to 

 coalesce with the formation of butter. 



(iii.) Carbohydrates. — The carbohydrate of the milk is 

 lactose (p. 286). It only occurs in milk. 



(4) Ash. — The ash of milk contains the same inorganic 

 substances as are found in the tissues (p. 636). The 

 substance present in greatest amounts are calcium and 

 phosphorus. Iron is present only in traces. 



3. The proportion in which constituents are present in 

 the milk of some species is shown in the following table : — 



(8) Percentage Composition. 



Cow. Goat. Mare. Sow. Bitch. 



The cells of the mammary gland transfer to the milk 

 many substances administered Avith the food, hence the taste 

 of the milk may be altered and certain drugs given by mouth 

 may appear in the milk. 



(4) Colostrum. — The fluid drawn from the gland for the 

 first two or three days after parturition diflers from true 

 milk. It is characterised by^ 



(1) A large proportion of solids — 25 to 30 per cent. 



(2) A high percentage of albumin and globulin. 



(3) The presence of multinuclear bodies, probably leuco- 

 cytes and desquamated glandular cells. 



