in medicine, is the dissolution of the aliment into such minute parts as are fit to enter the lacteal vessels, and circulate with the mass of blood.

Various are the systems and hypotheses framed by physicians and philosophers to account for digestion. Some contend, that it is done by a kind of elixation of the solid and groser parts of the food in the liquid by the heat of the stomach, and of the adjacent parts, the liver, spleen, &c. Others will have it done by attrition, as if the stomach, by those repeated motions, which are the effects of respiration, rubbed off the minuter particles from the groser matters, and agitating the rest against each other, attenuated and dissolved them.

Others think the bilious juice, others the spirits, chiefly concerned in digestion.

Others will have the food dissolved by a menstruum; but then they are greatly divided as to the nature and origin of this menstruum; some supposing it an acid furnished by the glands of the stomach; others, a nitro-aerial spirit, which, by penetrating the mass of food, breaks the connexion of the most solid parts; and others, a saline juice, which divides and volatilizes the parts of the food. Others, again, suppose digestion to be performed by means of a ferment or leaven, which mixing with the aliment, excites an intestine motion in the parts thereof, by which means the parts are attenuated and dissolved. But these likewise differ in their opinion of this ferment; some taking it to be the remains of the food last digested, which, by its continuance in the stomach, has contracted an acid quality and become a ferment: others take the principles of fermentation to be contained in the aliment itself, which when inclosed in the stomach, heated there, and put in motion, enters on its office of fermentation: others suppose the matter of the ferment supplied by the glands of the stomach; and lastly, others contend for the saliva, and make that the ferment serving principally for the digestion of the food.

Some suppose digestion owing to gentle heat and motion. By this heat and motion, say they, the texture of the nourishment is changed in the bodies of animals; and then the constituent solid parts are induced with peculiar attractive powers of certain magnitudes, by which they draw, out of the fluids moving through them, like parts in certain quantities, and thereby preserve their forms and just magnitudes. And, to mention no more, Boerhaave ascribes digestion to the joint action of several of the above-mentioned causes, aided by the expansion of the air contained in the aliments.

Want of Digestion, a disease attended with pain, and a sense of weight, with eruptions and copious flatulences from corrupt humours in the stomach.