RELATIVE VALUE OF FOOD. 153 



oat-straw 20 to 40, potatoes 20, pea-straw 10 to 15, old potatoes 40, 

 carrots 25 to 35, turnips 50, cabbage 20 to 30, peas and beans 3 to 5, 

 wheat 5 to 6, barley 5 to 6, oats 4 to 7, Indian corn 5, and oil-cake 2 

 to 4. Thus 6 Ibs. of oil-cake will nourish an animal as much as 

 40 Ibs. of potatoes, and 10 pounds of oats as much as 20 Ibs. of hay. 

 It is an important consideration, that in rich natural pastures there is a 

 mixed herbage, consisting of different plants, some abounding more in 

 starch or sugar, others more in gluten or albumen, and others more 

 in earthy or saline matter. The digestive organs select from these 

 such elements as are most required, and reject any surplus. Hence on 

 pastures occupied by one or two particular grasses, animals will not 

 thrive ; or, if they do, they must necessarily consume large quantities 

 to supply all the parts. Whenever, indeed, animals are fed on one 

 kind of vegetable only, there is a lack of the requisite elements of 

 animal composition ; so that a due mixture of the important constit- 

 uents of food being practised by nature, she should be copied by man. 



