It would appear probable that all the anatomical varieties in the structure of the stomachs of different animals may be resolved into their mechanical effects upon the aliment, as it seems that whatever be the nature of the food which is employed, if it be sufficiently comminuted or triturated, it is equally acted upon by the gastric juice. We find, indeed, that certain animals naturally confine themselves to certain kinds of food, and we must therefore conclude that such food is better adapted to the nature and constitution of the individual. But numerous ex

Cimento; Saggi de Esper. p. 268. Notwithstanding the expe riments of Spallanzani, § 27, 8, it appears that the food is not equally well digested without them, and we may easily conceive that they may contribute to the mechanical effect of the gizzard. Borelli, de Mot. anim. par. ii. prop. 192, 4, formed the extravagant idea, that these stones directly contributed to nutrition, an opinion which was opposed by Redi, who was aware of their real use; see Esperienze, p. 84, where he expressly says, "Quelle pietruzze sono come tante macinette raggirare da quei due forti et robusti musculi dé quali e composto ventriculo.. ;" also Osserv. p. 91, 2. Blumenbach, Comp. Anat. note 19, p. 145, 6, supposes that their especial purpose is to kill the grains, which, while alive, would resist the action of the gastric juice; but it is scarcely necessary to have recourse to this supposition. It has, however, been thought to receive some confirmation from the circumstance of the Pangolin, Manis pentadactyla, swallowing pebbles, for as its food consists of insects, which are not masticated, the pebbles have been supposed to be necessary for the purpose of crushing them, and thus depriving them of life, so as to render them more easily acted upon by the digestive fluids; p. 139. On the subject of these pebbles see also Hunter on the Anim. Econ. p. 196, 8; Fordyce on Digestion, p. 23, 4; Blumenbach, Spec. Physiol. Comp. p. 17.

amples are familiar to every one, where, either for the purpose of experiment, or from necessity, a total change has taken place, as for example, from an animal to a vegetable diet, or the reverse, without any apparent injury to the functions being produced, provided the mechanical texture of the food admits of its solution or minute division in the stomach.

§ 2. An Account of the Articles employed for Food.

The articles employed in diet may be classed under the two great divisions of animal and vegetable, each of them competent to the support of life, probably in all kinds of animals, although it would appear that, in most cases, one or the other is better adapted to the different species of them. From what has been stated above, it may be conceived, that this greater competency depends principally upon the mechanical properties of the substances, but they likewise differ considerably in their chemical nature, and this both with respect to their proximate principles and their ultimate elements. The ultimate elements of animal substances are oxygen, hydrogen, carbon, and nitrogen; vegetable substances contain oxygen, hydrogen, and carbon; but the proportion of carbon is generally greater, and of hydrogen less, while, for the most part they are either without nitrogen, or contain it in small quantity only.

Although there is reason to believe that every article of food which is received into the stomach, must experience a complete decomposition, and be assimilated into the state of chyme, before it can serve for nutrition, yet the successive steps of the

change, or the length of the process which it has to undergo, depends, in some measure at least, upon the similarity which there is between the alimentary' matter and the materials of which the body is composed. We therefore find that carnivorous animals, in general, have less bulky and less complicated organs than the herbivorous, and that among the latter, those that feed upon seeds or fruits, with the exception of the ruminants, have them less so, than those which live upon leaves or the entire vegetables. The stomach and intestines of man assimilate him, in regard to the nature of his diet, more to the herbivorous than to the carnivorous animals, yet we find, as a matter of fact, that either kind of diet is perfectly competent to his nutrition and support, and that probably the best state of health and vigour is procured by a due admixture of the two classes of substances.

4

We find, indeed, that mankind are principally guided in the choice of their food, with respect to its animal or vegetable origin, by the facility with which they are able to procure either the one kind or the other. The inhabitants of the northern regions,

5

4 Cuvier, Regne Anim. t. i. p. 86. Lawrence's Lect. p. 217. et seq. The reader who is disposed to pursue this inquiry, may peruse the learned dissertation of Richter, "de victus animalis antiquitate et salubritate," where he will find the subject treated in the true spirit of German research.

s See Haller, El. Phys. xix. 3. 3. The third section generally contains much useful and curious information respecting the different kinds of substances that have been employed in diet, either by nations or individuals; it is, however, liable to the imputation, from which many parts of this great work are not

where, at least during a considerable part of the year, vegetables could not be obtained, live almost entirely upon animal food, while in the warmer climates, where fruits and vegetables of all kinds are abundant, the diet is chiefly composed of these substances. We may remark, however, that this arrangement, although more a matter of necessity than of choice, is, on other accounts, the best adapted to their respective situations. An animal diet is probably better fitted for producing the vigour and hardihood of frame, which is requisite to brave the rigour of an arctic climate, while at the same time we may presume that it is more suited to the evolution of heat.

The proximate principles, or primary compounds of animal origin that are employed in diet, are fibrin, albumen, jelly, and oil, to which we may add sugar, osmazome, and some others of less importance. The animals that are employed in diet are taken prin- .

exempt, of the references being rather numerous than select. See also Lorry, Essai sur les Alimens; Plenk, Bromatologia; Richerand, El. Phys. § 3. p. 83; Sommering, Corp. Hum. fab. t. ii. p. 241, 250. § 157..161; Parr's Dict. Art. "Aliment;" Pearson's Syn. part 1; Lawrence's Lect. p. 201, 9; Thackrah's 2d Lect. on Diet, p. 54. et seq. Dr. Stark collected a series of facts respecting individuals, who had lived for a considerable length of time on some peculiar kind of diet; Works, p. 94, 5. His experiments on the effect produced by different kinds of aliment upon his own system, which he pursued with unexampled perseverance, afford a number of very curious results, but it would be impossible to give any synoptical view of them, consistent with the elementary nature of this work; see Journal, p. 96..168.

cipally from the mammalia, from birds, fish, the testacea, and the crustacea. The flesh of the mammalia and of birds consists chiefly of fibrin, together with a quantity of jelly united to it, especially in young animals. Milk, which from its destination as the food of the young animal immediately after birth, may be regarded as peculiarly adapted both for digestion and nutrition, consists of an emulsion of albumen, oil, and sugar, suspended in a large quantity of water. In the formation of cheese and butter, we abstract the greatest part of the water, and obtain the albumen and oil respectively in a state of greater or less purity according to the exact nature of the process which is employed. The eggs of birds, which likewise contain a peculiarly nutritive species of food, consist chiefly of albumen with a quantity of oily matter. Fish consist of a much greater proportion of albuminous and gelatinous matter, in some cases united with a considerable quantity of oil, and the same would appear to be the case with the testacea and the crustacea that are employed in diet. It is scarcely necessary to observe that the different kinds of soups consist nearly of the same proximate principles with the materials of which they are composed, a portion of the firm and dense substances being rejected, while the more soluble parts are dissolved, or, perhaps, rather suspended in the water, consisting therefore of fibrin, albumen, jelly, or fat, according to the age of the animal, or the part of it which is employed.

The vegetable products, which compose any considerable portion of our diet, are fruits, seeds, roots,