DIGESTION 323 



and convincing experiments of Beaumont that the foundation 

 of our exact knowledge of its composition and action was laid. 



It is difficult to speak without enthusiasm of the work of Beaumont , 

 if we consider the difficulties under which it was carried on. An 

 army surgeon stationed in a lonely post in the wilderness that was 

 then called the territory of Michigan, a thousand miles from a 

 University, and four thousand from anything like a physiological 

 laboratory, he was accidentally called upon to treat a gun-shot 

 wound of the stomach in a Canadian voyageur, Alexis St. Martin. 

 When the wound healed a permanent fistulous opening was left, by 

 means of which food could be introduced into the stomach and 

 gastric juice obtained from it. Beaumont at once perceived the 

 possibilities of such a case for physiological research, and began a 

 series of experiments on digestion. After a while, St. Martin, with 

 the wandering spirit of the voyageur, returned to Canada without 

 Dr. Beaumont's consent and in his absence. Beaumont traced him, 

 with great difficulty, by the help of the agents of a fur-trading 

 company, induced him to come back, provided for his family as well 

 as for himself, and proceeded with his investigations. A second 

 time St. Martin went back to his native country, and a second time 

 the zealous investigator of the gastric juice, at heavy expense, secured 

 his return. And although his experiments were necessarily less 

 exact than would be permissible in a modern research, the modest 

 book in which he published his results is still counted among the 

 classics of physiology. The production of artificial fistulas in animals, 

 a method that has since proved so fruitful, was first suggested by 

 his work. 



Gastric juice when obtained pure, as it can be from an acci- 

 dental fistula in man, or, better, by giving a dog with an oeso- 

 phageal as well as a gastric fistula a ' sham-meal ' (p. 374), is a 

 clear, thin, colourless liquid of low specific gravity (in the dog 

 1003 to 1006) and distinctly acid reaction. The total solids 

 average about 5 parts per thousand, of which the ash (chiefly 

 sodium and potassium chloride, with small quantities of calcium 

 and magnesium phosphate) represents about a fourth, and heat- 

 coagulable substances (proteins, nucleoprotein) about a third. 

 None of these has any special importance in digestion. Of 

 quite a different significance are the three ferments present : 

 pepsin, which changes proteins into peptones ; rennin, which 

 curdles milk (but see p. 327) ; and a fat-splitting ferment which, 

 under certain conditions at least, splits up emulsified neutral 

 fats e.g., the fat of milk into glycerin and fatty acids, but 

 has no action upon non-emulsified fat. The acidity is due to 

 free hydrochloric acid, the other important constituent of the 

 juice. In the dog the proportion of this acid varies from 0-46 to 

 0-58 per cent. In such analyses as have been made of approxi- 

 mately pure human gastric juice a smaller percentage of hydro- 

 chloric acid has usually been obtained (at most 0-35 to 0-4 per 

 cent.). But there is some reason to believe that if the human 

 juice could be collected in a faultless manner, and especially free 



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