384 
DIGESTION VISIBLE TO THE EYE. 
“ Having proceeded so far. Dr. Beaumont next endeavoured to 
discover at what time the gastric juice begins to be poured out, 
and under what conditions its secretion is carried on ; and here 
again ocular inspection afforded him satisfactory results. 
“ It has already been remarked, that, on pushing back the 
valve which filled up the opening into the stomach, the cavity 
within became visible to a considerable extent ; and that when 
St. Martin lay for a time on the left side, a portion of the 
villous coat, large enough to exhibit several inches of its surface, 
generally protruded. Owing to these circumstances. Dr. Beau- 
mont could easily observe what changes occurred, both when 
food was swallowed in the usual way, and when it was intro- 
duced at the opening left by the wound. Accordingly, on exam- 
ining the surface of the villous coat with a magnifying glass, he 
perceived an immediate change of appearance ensue whenever 
any aliment was brought into contact with it. The action of the 
neighbouring bloodvessels was instantly increased, and their 
branches dilated so as to admit the red blood much more freely 
than before. The colour of the membrane consequently changed 
from a pale pink to a deeper red, the vermicular or worm-like 
motions of the stomach became excited, and innumerable minute 
lucid points and very fine nervous and vascular papillae could be 
seen arising from the villous coat, from which distilled a pure, 
colourless, and slightly viscid fluid, which collected in drops on 
the very points of the papillae, and trickled down the sides of the 
stomach till it mingled with the food. This afterwards proved 
to be the secretion peculiar to that organ, or, in other words, the 
true gastric juice ; the mucous fluid secreted by the follicles, 
which some have mistaken for it, is not only more viscid, but 
wants altogether the acid character by which it is generally dis- 
tinguished. 
“ Pursuing his experiments, Dr. Beaumont then found that 
the contact not only of food but of any mechanical irritant, such 
as the bulb of a thermometer, or other indigestible body, invari- 
ably gave rise to the exudation of the gastric fluid from these 
vascular papillae; but that, in the latter cases, the secretion al- 
ways ceased in a short time, as soon, apparently, as the organ 
could ascertain that the foreign body was one over which the 
gastric juice had no power. But the small quantity obtainable 
in this way is, perhaps, more pure and free from admixture, and 
therefore better adapted for examination, than any which can be 
procured under any other circumstances. 
“ Gastric juice, in its purest form, and unmixed with any 
thing except the small portion of mucus from which it can never 
be obtained entirely free, is described by Dr. Beaumont to be a 
