Johnson also remarks, in this connection, that the great value of linseed-cake, as an adjunct to hay for fat cattle and milch cows, has long been recognized; and is undeniably traceable in the main to three ingredients of the seeds of the oil-yielding plants. The value of food depends upon the quantity of matters it contains which may be appropriated by the animal which consumes the food. Now, it is proved that the fat of animals is derivable from the _starch_, _gum_, and _sugar_, and more directly and easily from the _oil_ of the food. These four substances are, then, the _fat-formers_. The muscles, nerves, and tendons of animals, the fibrine of their blood, and the curd of their milk, are almost identical in composition, and strongly similar in many of their properties with matters found in all vegetables, but chiefly in such as form the most concentrated food. These _blood_ (and muscle) _formers_ are characterized by containing about fifteen and a half per cent. of nitrogen; and hence are called _nitrogenous substances_. They are also often designated as the _albuminous bodies_. The bony framework of the animal owes its solidity to _phosphate of lime_, and this substance must be furnished by the food. A perfect food must supply the animal with these three classes of bodies, and in proper proportions. The addition of a small quantity of a food rich in oil and albuminous substances to the ordinary kinds of feed, which contain a large quantity of vegetable fibre or woody matter, more or less indigestible, but nevertheless indispensable to the herbivorous animals, their digestive organs being adapted to a bulky food, has been found highly advantageous in practice. Neither hay alone nor concentrated food alone gives the best results. A certain combination of the two presents the most advantages. A Bavarian farmer has recently announced that heifers fed, for three months before calving, with a little linseed-cake, in addition to their other fodder, acquire a larger development of the milk-vessels, and yield more milk afterwards, than similar animals fed as usual. Cotton-seed cake must have an equally good effect. Some of those who have used cotton-seed cake have found difficulty in inducing cattle to eat it. By giving it at first in small doses, mixed with other palatable food, they soon learn to eat it with relish. On comparing the analyses II. and I. with the average composition of linseed-cake IV., it will be seen that the cotton-seed cake is much richer in oil and albuminous matters than the linseed-cake. A correspondingly less quantity will therefore be required. Three pounds of this cotton-seed cake are equivalent to four of linseed-cake of average quality.