the world chestnuts, figs, dates, and the Quinoa goosefoot, are eaten as substantive articles of food. But you will remark that no food is used as a principal support of man unless it contains from 6 to 8 per cent. of flesh-forming matters.

ON ANIMAL FOOD.

In this Lecture I purpose speaking of those fleshforming substances which we obtain from the animal kingdom. I told you in my last Lecture, that all that which constitutes the flesh of animals-that which forms the muscles and the nerves, and which we eat as food, is derived from the vegetable kingdom-from plants. There would be no flesh unless animals first fed on the vegetable kingdom-on plants. If some animals are carnivorous, we find that they feed on those animals which are granivorous or herbivorous. Thus the ox and the sheep, and various kinds of birds, all feed on grass or grain, and the flesh which we obtain from them they have derived from the plant. The plant, you will recollect, produces this flesh-forming matter in the interior of its cells, where it is known by the names of the

nucleus, the cytoblast, the protoplasm, the primordia utricle, and the endoplast.

I have now to speak of the things that have thus been obtained from the plant, appropriated by animals, and made to subserve the purposes of man as articles of diet.

In casting around for something like a form of food that we could regard as a type of all others, there is none better than milk; and as milk is an animal product, I shall speak of it in detail to day. Milk really represents all the food of which we partake which is not medicinal. That milk is a type of all food, is found in the fact that the young of all the higher mammalia are fed on this food for several months many of them for above a year, and get no other, article of diet. During this period they grow very rapidly, and increase in size; consequently, they must have obtained all that which constitutes their muscle, other tissues, the heat

their nerve, their bone, and they give out and the force they exert from the milk they have taken : so that, you see, milk must contain the essentials of all food; and is worthy our attentive investigation.

oz. of

Let us, then first study the composition of milk. A pound of cow's milk contains about 13 oz. of water, which is the first substance we spoke of in these Lectures; then it contains about oz. of mineral matter, of which we spoke in our second Lecture; sugar, of which we spoke in the third Lecture; oz. of butter, one of the oily substances of which we spoke in the fourth Lecture; and then it also contains oz. of caseine, of which we spoke in the last Lecture; so that, you see, milk contains representatives of

all the groups of human food. Nor do I wish you to think that such a view has in any manner originated with myself. I would here refer to a classification of food according to the late Dr. Prout, and we are probably more indebted to Dr. Prout than any other investigator in advancing our knowledge of the action of food; for before Mulder had made his great discovery, and Liebig had written and made this subject so popular, Dr. Prout had produced his celebrated work on the Stomach, in which he pointed out that milk may be taken as the type of human food. He divided food into four groups: first, the aqueous, embracing water, tea, coffee, and other watery beverages; then the second group he called saccharine, embracing such substances as sago, arrowroot, sugar, and sweet fruits, and containing from 40 to 50 per cent. of carbon; then came the albuminous group, represented by cheese and the flesh of mammals, birds, and fish; and, lastly, the oleaginous group, containing 70 to 80 per cent. of carbon, and represented by butter. Now, the deficiency of this classification is, that it does not allow for the value of the salts or mineral substances as food, which were spoken of in the second Lecture.

Different animals yield milk of a different composition, and we find a variety of these milks employed by man as food. The milk of the cow is more constantly employed in this country than any other; but in some countries the milk of the goat stands in the same relation to the popular diet as the milk of the cow does here. Again, in disease, recourse is had to asses' milk; and thus it becomes of importance that we should know something of the composition of milks.

We are not at all likely in this country to get goats' milk, but the milks we use are cows' milk and asses' milk. I have here the analyses of these milks and of human milk, and you may easily compare these milks one with the other.

1 lb. of Cows' milk contains

oz. gr.

The milk of the mother frequently fails, and it becomes a question of importance to know what is the best substitute. Now, cows' milk is the readiest and cheapest expedient, but frequently asses' milk is preferred; because, if you take the quantity of caseine, sugar, and butter, they are nearly alike in human and asses milk; but cows' milk contains more caseine, more flesh-giving matter. Hence the practice, when cows' milk is given to children, of adding half the quantity of water; and then,.in order to supply the deficiency of