It is an important point in the composition of oil-cakes, that they contain a large proportion of ready-formed fatty matters which can, with but little alteration, be at once transmuted into animal fat. There are some individuals of the genus _Homo_ to whose stomachs fat, _per se_, is intolerable; nevertheless, as a general rule, fatty substances exercise a favorable influence in the process of digestion, and, either in a separate state, or intimately commingled with other aliments, constitute a large proportion of the food of man. Digestion in the lower animals is, no doubt, similarly promoted by mixing with the aliments which are to be subjected to that process, a due proportion of oily or fatty matter. Straw is relatively deficient in the flesh-forming principles, and abounds in the fat-forming elements--of which, however, the most valuable, oil, is the least abundant. Now, if we add to straw a due proportion of some substance very rich in flesh-formers and oil, the compound will possess in nicely adjusted proportions all the elements of nutrition. Perhaps the best kind of food which we could employ for this purpose is linseed meal. It contains about 24 per cent. of flesh-formers, 35 per cent. of a very bland oil, and 24 per cent. of gum, sugar, and mucilage. Linseed-cake may be substituted for linseed-meal; but the meal, though its cost is 15 per cent. greater, is, I believe, rather the better article of the two. Its flesh-formers are more soluble, and its oil thrice more abundant and far more palatable than the same principles in most samples of oil-cake. An important point, too, is, that linseed, unlike linseed-cake, is not liable to adulteration. As linseed possesses laxative properties it cannot be largely employed; the addition, however, of bean-meal--the binding tendency of which is well known--to a diet partly composed of linseed will neutralise, so to speak, the relaxing influence of the oily seed. If oil-cakes be used as an adjunct to straw, rape-cake will be found more economical than linseed-cake. If it be free from mustard, well steamed, and flavored with a little treacle, or a small quantity of locust-beans, it will be readily consumed, and even relished, by dairy and fattening stock. _Hay._--There is no food substance more variable or more complex than hay, for under that term are included, not only mixtures of grasses, but also of leguminous plants--clover, for example. The herbage of no two meadows is exactly alike; and the composition of the meadow plants is so greatly modified by differences of climate, soil, and mode of culture, that we have nothing to excite our wonder in the extreme variability of hay. The composition of the hay made from clover, lucerne, and various other kinds of artificial grasses, is shown in the table--which is based on the results of Way's analyses:-- COMPOSITION OF THE HAY OF ARTIFICIAL GRASSES.