From the existence of this intentional relation between mastication and the salivary secretion, the latter is always most copious in those creatures whose food requires continued mastication. In ruminating animals, accordingly, the salivary glands are numerous and of great size, while they are at the same time so situated that the play of the muscles in the act of rumination communicates to them a proportionate stimulus. In those, again, which do not masticate at all, but swallow their food entire, there is scarcely any salivary secretion, and the glands appropriated to it are very small. Birds, and many fishes and reptiles, belong to the latter class. From the foregoing explanation of the object and conditions of mastication, the reason will be apparent why _fluids_ do not require to undergo that process, and also why dry mealy substances stand in need of protracted chewing before they can be easily swallowed. When hot spicy food is taken into the mouth, the secretion of saliva is immensely increased, obviously for the purpose of diluting the excess of stimulant before it shall be allowed to reach the stomach. But when the food is of a mild and unirritating quality, much dilution is unnecessary, and the secretion is accordingly moderate. The chief purpose of mastication, then, is evidently the minute division of the aliment, so as to admit of its being easily acted upon by the gastric juice when received into the stomach. Dr Beaumont, however, seems to me to go too far in inferring, that “if the _materia alimentaria_ could be introduced into the stomach in a finely divided state, the operations of mastication, insalivation, and deglutition, would not be necessary.” It would require a more extensive range of experiments than that which he has made, to prove that “aliment is as well digested and assimilated, and allays the sensation of hunger as perfectly, when introduced directly into the stomach (through an opening in the side) in a proper state of division, as when the usual previous steps have been taken.”[15] It is quite true that mastication and deglutition are chiefly mechanical processes; but it is difficult to believe that so much care would have been taken to provide a proper supply of fluid of a constant and _peculiar_ character like saliva, if water were capable of answering the purpose as well, and if saliva were useful _only_ in lubricating the food. There subsists, moreover, between the sense of taste and the power of digestion a certain relation, which renders it more than probable that the active gratification of the former during mastication, is favourable to the production and flow of nervous energy towards the stomach, and consequently in so far conducive to the healthy performance of digestion that even in that point of view insalivation could not easily be dispensed with. Dr Beaumont’s experiments, however, abundantly demonstrate that Montègre, and those who, along with him,