420 OF FOOD, AND THE DIGESTIVE PROCESS. 



tion of pepsin, or perhaps upon another substance accompanying it, which ceases 

 to be formed when the young animal is no longer nourished by the milk of its 

 mother." 1 



443. It is only when either alimentary or some other substances capable of 

 exciting irritation are present in the Stomach, that this acid secretion is poured 

 forth. So long as it is empty, the secretion which moistens its walls is neutral 

 or even alkaline; but, as soon as food is taken, acid is poured forth, and this in 

 increasing quantities, until a certain time after the commencement of the digest- 

 ive process, when the acidity of the stomach is at its maximum. In proportion 

 as the alimentary matter is dissolved, however, and is either at once absorbed, 

 or escapes through the pyloric orifice, the acidity of the stomach diminishes ; and 

 as soon as its cavity is emptied, the secretion of its walls is neutral again. 2 

 A very important series of observations on the conditions under which the 

 Gastric juice is secreted, was made some years since by Dr. Beaumont, in the 

 remarkable case of Alexis St. Martin, already several times referred to. 3 "The 

 inner coat of the stomach (as seen through the fistulous orifice) in its natural 

 and healthy state, is of a light or pale pink color, varying in its hues, according 

 to its full or empty state. It is of a soft or velvet-like appearance, and is con- 

 stantly covered with a very thin, transparent, viscid mucus, lining the whole 

 interior of the organ. By applying aliment or other irritations, to the internal 

 coat of the stomach, and observing the effect through a magnifying glass, in- 

 numerable lucid points, and very fine [nervous or vascular] papillae can be seen 

 arising from the villous membrane, and protruding through the mucous coat, 

 from which distils a pure, limpid, colorless, slightly viscid fluid." (The papillae 

 here described appear to be the orifices of the gastric follicles, which are usually 

 closed by their epithelial cells during fasting, and which would seem to become 

 prominent when the vis d tergo of the secreted fluid first causes this plug of cells 

 to be cast forth.) "The fluid thus excited is invariably distinctly acid. The 

 mucus of the stomach is less fluid, more viscid or albuminous, semi-opaque, 

 sometimes a little saltish, and does not possess the slightest character of acidity. 

 The gastric fluid never appears to be accumulated in the cavity of the stomach 

 while fasting ; and is seldom, if ever, discharged from its proper secerning 

 vessels, except when excited by the natural stimulus of aliment, mechanical 

 irritation of tubes, or other excitants. When aliment is received, the juice is 



fiven out in exact proportion to its requirements for solution, except when more 

 >od has been taken than is necessary for the wants of the system. "-^-The ob- 

 servations of Dr. Beaumont have been confirmed by those of M. Blondlot 4 and 

 of M. Cl. Bernard, 5 which were made upon Dogs, in whose stomachs fistulous 

 openings were maintained for a length of time. They found that the flow of 

 gastric fluid is more excited by pepper, salt, and soluble stimulants, than it is 

 by mechanical irritation ; and that if mechanical irritation be carried beyond 

 certain limits, so as to produce pain, the secretion, instead of being more abund- 

 ant, diminishes or ceases entirely; whilst a ropy mucus is poured out instead, 

 and the movements of the stomach are considerably increased. The animal at 

 the same time appears ill at ease, is agitated, has nausea, and, if the irritation 

 be continued, actual vomiting; and bile has been observed to flow into the 

 stomach, and escape by the fistulous opening. Similar disorders of the func- 

 tions of the stomach result from violent pain in other parts of the body; the 



1 Prof. Graham's "Elements of Chemistry," p. 697, Am. Ed. 

 a See Dr. Bence Jones, in " Medical Times," June 14, 1852. 



3 See Dr. Beaumont's "Experiments and Observations on the Gastric Juice and the 

 Physiology of Digestion," reprinted with notes by Dr. Andrew Combe, Edinb., 1838. 

 * "Traite Analytique de la Digestion." 

 6 "Archiv. d'Anat. Gn. et de Physiol.," Jan. 1846. 



