ANIMAL CHEMISTRY. 403 



kinds of food together. Thus the Irishman eats with his 

 potatoes buttermilk for the casein it contains, or cabbage, 

 which is one of the vegetables that is rich in nitrogen. The 

 Italian for the same reason adds cheese to his macaroni, and 

 the wayfaring Spaniard eats with his bread an onion or two, 

 this vegetable containing much nitrogen, like the cabbage 

 of the Irishman.* So pork, which is only heat-food, is eaten 

 with cabbage or beans, butter with bread, and oil with salad. 

 Experiments which have been tried show decidedly that 

 life can be sustained only on mixtures of food. Animals 

 have been fed on various single substances extracted from 

 articles of food, and the results have always been bad, even 

 to the destruction of life. This is true of the nitrogenous 

 constituents as well as the carbonaceous. The fibrin ex- 

 tracted from meat is far from answering the same purpose 

 as the meat itself. The juices of the meat are needed 

 in combination with the fibrin to accomplish the full pur- 

 poses of nutrition. It may be laid down as a general truth 

 that no separated principles of food answer the same end 

 as the mixtures which are produced in nature. The gluten 

 of wheat does better than any other one thing, but this 

 alone is by no means as good food as its mixture in the 

 grain with starch and albumen. 



572. Milk. It is worthy of remark here that milk, the 

 only mixture of food which nature has provided as the sole 

 means of nutrition for some animals the mammalia in 

 their infancy, has the two kinds of food combined, the 



* The dish so common in Ireland called Kol-cannon is prepared by beat- 

 ing potatoes and boiled cabbage together, putting in a little pork-fat, salt, 

 and pepper. Johnston says of this, " Take a pot-bellied potato-eater and 

 feed him on this dish, and he will become not only stronger and more act- 

 ive, but he will cease to carry before him an advertisement of the kind of 

 food he lives upon, and his stomach will fall to the dimensions of the same 

 organ in other men." 



