641. Muriatic acid, the chemical agent by which the stomach dissolves the food, is probably obtained from the muriate of soda (common salt) contained in the blood. The soda, the basis of the salt, would appear to be retained in the blood, to preserve the alkaline condition essential to the maintenance of the sound constitution of the blood, while the muriatic acid, disengaged from the soda in the process of secretion, is poured into the stomach to act upon the food. 642. A remarkable confirmation of the correctness of the general conclusions to which observation and experiment had thus enabled physiologists to arrive, is afforded by the case of a young soldier in the American army, of the name of Alexis St. Martin, who received a wound on the left side by the accidental discharge of a musket. The charge, which consisted of duck shot, and which was received at the distance of one yard from the muzzle of the gun, entered the side posteriorly in an oblique direction, forward and inward; blew off the integument and muscles to the size of a man’s hand; fractured and carried away the anterior half of the sixth rib; fractured the fifth rib; lacerated the lower portion of the left lobe of the lungs; lacerated the diaphragm, and perforated the stomach. 643. Violent fever and extensive sloughing of the parts injured ensued, and the life of the young man was often in jeopardy, but he ultimately recovered. At the distance of about a year from the date of the accident, the injured parts had all become sound, with the exception of the perforation into the stomach, which never closed, but left an aperture permanently open, two inches and a half in circumference. This aperture was situated about three inches to the left of the cardia, near the left superior termination of the great curvature. For some time the food could be retained only by constantly wearing a compress and bandage; but at length a small fold of the mucous coat of the stomach appeared, which increased until it completely filled the aperture and acted as a valve, so as effectually to prevent any efflux from within, while it admitted of being easily pushed back by the finger from without: when the stomach was nearly empty, it was easy to examine its cavity to the depth of five or six inches by artificial distension; but, when entirely empty, the stomach was always contracted on itself, and the valve generally forced through the orifice, together with a portion of the mucous membrane equal in bulk to a hen’s egg. 644. It chanced that the admirable opportunity thus afforded of bringing the process of digestion, as far as it is carried on in the stomach, under the cognizance of sense, occurred to an observant and philosophical mind, and it was not lost.[6] The following are some of the curious and instructive phenomena observed. [6] Experiments and Observations on the Gastric Juice, and the Physiology of Digestion. By W. Beaumont, M.D., Surgeon in the U. S. Army. Boston. 1834.