DIGESTIVE POWER OF GASTRIC FLUID. 223 



destroys the digestive property of the fluid. For the perfec- 

 tion of the process also, certain conditions are required, which 

 are all found in the stomach ; namely (1), a temperature of 

 about 100 F. ; (2), such movements as the food is subjected 

 to by the muscular actions of the stomach, which bring in suc- 

 cession every part of it in contact with the mucous membrane, 

 whence the fresh gastric fluid is being secreted ; (3), the con- 

 stant removal of those portions of food which are already 

 digested, so that what remains undigested may be brought 

 more completely into contact with the solvent fluid ; and (4) 

 a state of softness and minute division, such as that to which 

 the food is reduced by mastication previous to its introduction 

 into the stomach. 



The chief circumstances connected with the mode in which 

 the gastric fluid acts upon food during natural digestion, have 

 been determined by watching its operations when removed 

 from the stomach and placed in conditions as nearly as possi- 

 ble like those under which it acts while within that viscus. 

 The fact that solid food, immersed in gastric fluid out of the 

 body, and kept at a temperature of about 100, is gradually 

 converted into a thick fluid similar to chyme, was shown by 

 Spallanzani, Dr. Stevens, Tiedemann and Gmelin and others. 

 They used the gastric fluid of dogs, obtained by causing the 

 animals to swallow small pieces of sponge, which were subse- 

 quently withdrawn, soaked with the fluid and proved nearly 

 as much as the latter experiments of the same kind of gastric 

 fluid by Blondlot, Bernard and others. But these need not 

 be particularly referred to, while we have the more satisfac- 

 tory and instructive observations which Dr. Beaumont made 

 with the fluid obtained from the stomach of St. Martin. 

 After the man had fasted seventeen hours, Dr. Beaumont took 

 one ounce of gastric fluid, put into it a solid piece of boiled 

 recently salted beef weighing three drachms, and placed the 

 vessel which contained them in a water-bath heated to 100. 

 " In forty minutes digestion had distinctly commenced over 

 the surface of the meat ; in fifty minutes, the fluid had become 

 quite opaque and cloudy, the external texture began to separate 

 and become loose ; and in sixty minutes chyme began to form. 

 At 1 P.M." (two hours after the commencement of the experi- 

 ment) " the cellular texture seemed to be entirely destroyed, 

 leaving the muscular fibres loose and unconnected, floating 

 about in small fine shreds, very tender and soft." In six hours, 

 they were nearly all digested a few fibres only remaining. 

 After the lapse of ten hours, every part of the meat was com- 

 pletely digested. The gastric juice, which was at first trans-; 

 parent, was now about the color of whey, and deposited a fine 



