Some have expressed surprise that animals have refused to thrive, and have ultimately died, when fed upon animal jelly or gelatine (from bones) alone, nourishing though that substance _as part of the food_ undoubtedly is. When given in sufficient quantity, gelatine might indeed supply carbon enough for respiration, with a great waste of nitrogen, but it is deficient in the saline ingredients which a naturally nourishing food contains. Even on the natural mixture of starch and gluten in fine white bread, dogs have been unable to live beyond 50 days, though others fed on household bread, containing a portion of the bran—in which earthy matter more largely resides—continued to thrive long after. It is immaterial whether the general quantity of the _whole_ food be reduced too low, or whether _one_ of its necessary ingredients only be too much diminished or entirely withdrawn. In either case, the effect will be the same—the animal will pine away, and sooner or later die. SECTION VII.—OF THE PRACTICAL AND THEORETICAL VALUE OF DIFFERENT KINDS OF FOOD. From what has been stated in the preceding section, it appears, that, for various reasons, different kinds of food are not equally nourishing. This fact is of great importance, not only in the preparation of human food, but also in the feeding of stock. It has, therefore, been made the subject of experiment by many practical agriculturists, with the following general results. If common hay be taken as the standard of comparison, then to yield the same amount of nourishment with 10 lbs. of hay, a weight of the other kinds of food must be given, which is represented by the number opposite to each in the following table:— Hay, 10 Carrots, 25 to 30 Clover hay, 8 to 10 Turnips, 50 Green clover, 45 to 50 Cabbage, 20 to 30 Wheat straw, 40 to 50 Pease and Beans, 3 to 5 Barley straw, 20 to 40 Wheat, 5 to 6 Oat straw, 20 to 40 Barley, 5 to 6 Pea straw, 10 to 15 Oats, 4 to 7 Potatoes, 20 Indian corn, 5 Old potatoes, 40? Oil-cake, 2 to 4 It is found in practice, as the above table shews, that twenty stones of potatoes or three of oil-cake will nourish an animal as much as ten stones of hay, and five stones of oats as much as either. Something, however, will depend upon the quality of each kind of food, and upon the age and constitution of the animal. The skilful feeder of stock knows also the value of a change of food, or of a mixture of the different kinds of vegetable food he may have at his command.