Exposed to the action of all the agents above enumerated, and to the increased nervous and vascular excitement which are necessary during digestion, a singular change soon commences in the food, and goes on till chymification is completed. After a little while the contents of the stomach, whatever their nature and variety, begin to be converted into a substance of a homogeneous, soft, greyish, and viscid appearance, of a sweetish, _fade_, and slightly acid taste, but which still preserves some of the qualities of the food, and is called chyme. The chyme always forms on that part of the food with which the gastric juice is in immediate contact; and, in proportion as it is produced, it is carried gradually onwards by the gentle motion of the stomach towards the pylorus, where consequently it always exists in the greatest quantity. At the cardiac or left end of the stomach it is most sparingly found, both because digestion is there only beginning, and because the chyme is speedily removed from it and carried away towards the pylorus. The doctrine hitherto generally received, and held by Dr Wilson Philip and others as demonstrated, is, that “the layer of food lying next to the surface of the stomach is first digested, and in proportion as this undergoes the proper change, and is moved by the muscular action of the stomach, that next in turn succeeds, to undergo the same change.” Dr Beaumont, however, declares, that, whatever may be the case in rabbits and other animals on which Dr Philip’s experiments were made, such was not the order observed in the stomach of Alexis St Martin--and such, he naturally infers, is not the order in the human stomach in general. Nor is such, I may add, the order which either experience or a correct view of the antecedent circumstances and physiological conditions ought to lead us to anticipate. When vomiting, for instance, occurs an hour or two after a meal composed of different ingredients has been swallowed, no such separation into digested and undigested portions is to be found, but the whole are observed to have undergone changes proportioned to their degrees of digestibility, whether they were eaten first or last.