In the dispute, whether man be natu rally carnivorous or herbivorous, we are inclined to suppose that truth lies on neither side. That the structure both of the teeth and intestines, as well as of the joint of the lower jaw, occupies a middle place between the two just mentioned, and constitutes him an omnivorous ani mal. This, indeed, seems to follow ne cessarily from the unlimited extent of his habitation ; he can dwell in every coun try and climate of the globe ; and makes use, in various situations, of every variety of alimentary matter, furnished by the animal and vegetable kingdoms.
The food of man, and probably of every animal, is derived from organized matter. Nothing seems capable of furnishing nourishment that has not lived : the mi neral kingdom, indeed, supplies some ar ticles of seasoning, which are mixed with our food, and various medicines and poisons, which do not seem to be nu tritious.
As .man on the one hand is a most truly omnivorous animal, and capable of con venting into nourishment almost every production of the animal and vegetable kingdoms, so on the other side he may continue strong and healthy although using one, and that a very simple kind of aliment. A woman, whose case is related in the memoirs of the Medical Society of Edinburgh, lived on whey for fifty years. Many men live only on certain vegeta bles, as potatoes, chesnuts, dates, &c. Some wandering Moors, according to Adamson, live almost entirely on gum Senegal. Fish is the only food of nume rous uncivilized tribes on different coasts : and flesh of others. Some barbarous hordes still eat raw meat, and even the human body sometimes serves them as a repast. In several islands between the tropics, particularly in the South Sea, there is no fresh water, and the milk of the cocoa-nut is used instead : various other singular facts relating to the food and drink of man, might be collected here, showing very clearly that he is an omnivitous animal.
be the diversity of food, the action of our organs always separates the same nutritive principle from it : in fact, let the diet be totally vegetable, or totally animal, the peculiar composition of our organs does not alter, an evident proof that the matter we extract from aliment to appropriate to ourselves, is always alike.
It has been a matter of dispute, whether pure water furnish any nourishment, or be a mere diluent.
We have nothing further to say con cerning the processes of mastication and deglutition, than what the reader will find in the article ANATOMY, under the head of " Organs of Mastication and De glutition." Salivary Secretion. This has been es timated by Nuck at the quantity of one pint in twenty-four hours. Although it probably goes on, to a certain degree, at all times, yet it is more copious when we take food; and the augmentation of quan tity arises partly from stimulus, partly from mechanical pressure. When any acrid matter is taken into the mouth, an increased flow of saliva is produced; and this may also follow the mere sight of food, and hence has arisen the well-known expression of the " mouth watering." All the salivary glands are so situated that the motions of the jaw, and other in struments of mastication, necessarily sub jects them to considerable pressure, by which their secretory tubes are evacuat ed, and new secretion promoted.
The saliva is conveyed into the mouth by the contractile power of the salivary ducts, which, in some rare instances, are said to have projected it even from the cavity of the mouth. The great number of vessels and nerves which belong to, and are placed near these glands, correspond to the copious supplies of fluid which they furnish.
Besides the simple water furnished by the true salivary glands, the mucous fol licles, which abound on the surface of the mouth supply a considerable proportion of that fluid, to be mixed with the food. These additions being, by means of mas. tication, intimately blended with the food, not only reduce it to a soft pultaceous mass, more fit for the process of deglu tition, but also bring it into a state of con venient preparation for the subsequent process of digestion and assimilation. In this point of view, mastication is very im portant, as we may observe from the ill effects which ensue when the loss of the teeth renders it imperfect in old persons.
For the chemical analysis of SALIVA, the reader will look to that word ; and for an account of the digestive process itself, to the article DIETETICS; in which are also several observations respecting food.