MILK AS A FOOD 51 



and casein content, averaging about 9 per cent of fat and 

 about 6.3 per cent of casein. 



Mare's milk is usually distinctly alkaline in reaction, but 

 may be neutral. It is white or bluish in color and has a 

 somewhat pronounced sweet taste, due to the fact that it 

 has a comparatively high percentage of milk sugar, namely, 

 6.6 per cent. The proportions of fat and proteins in mare's 

 milk is conspicuously small, only 1.09 per cent of fat and 

 1.89 per cent of protein. 



Ass's milk is essentially the same as that of mare's, and 

 has in common with the latter a low fat and protein con- 

 tent and a large quantity of milk sugar. The milk of the 

 ass more nearly resembles human milk than does that of 

 any other animal, and in portions of Europe, for the most 

 part, milk of the ass is the principal substitute used for 

 the nourishment of infants. 



Sow's milk is thick, slimy, and alkaline in reaction. Its 

 chemical composition is very variable, especially so in re- 

 gard to the fat content, which varies from 1 to more than 

 12 per cent. The quantity of protein averages about 6 per 

 cent, but may vary from 5.7 to 15.5 per cent. The milk 

 sugar varies from 2 to 3.8 per cent. 



Bitch's milk is also quite variable in its composition, and 

 the milk of the cat has not received much study. The rab- 

 bit and reindeer give milk particularly rich in fat and espe- 

 cially concentrated, but poor in milk sugar. The elephant 

 shows very great fat and sugar content and comparatively 

 little protein. 



Whale's milk differs greatly from that of land animals. 

 It contains only from 41 to 48 per cent of water, and fat in 

 the enormous proportion of 43 to 45 per cent. There is 7.5 

 to 11 per cent of protein, and only about 1.3 per cent of 

 sugar. Dolphin's milk is also highly concentrated, con- 

 taining only about 41 per cent of water. 



Zebu's milk has almost exactly the same properties and 

 composition as ordinary cow's milk. 



