685 

 



appearing first from the base of the cell, which then becomes filed 

 with a non-granular material. Observations similar to those ma^^ 

 upon other glands demonstrate that these granules represent in 

 probability a preliminary material from which the gastric enzym 

 are made during the act of secretion. The granules, therefore, 

 sometimes described as zymogen granules. 



Means of Obtaining the Gastric Secretion and its Normal 

 Composition. The secretion of the gastric membrane is formed in 

 the minute glands scattered over its surface. As there is no com- 

 mon duct, the difficulty of obtaining the secretion for analysis or 

 experiment is considerable. This difficulty has been overcome at 

 different times by the invention of special methods. 



The older methods used for obtaining normal gastric juice were 

 very unsatisfactory. An animal was made to swallow a clean 

 sponge to which a string was attached so that the sponge could 

 afterward be removed and its contents be squeezed out ; or it was 

 made to eat some indigestible material, to start the secretion of 

 juice by mechanical stimulation: the animal was then killed at the 

 proper time and the contents of its stomach were collected. 



The experiments of the older observers on gastric digestion, especially 

 those of the Abbe Spallanzani (1729-1799), furnish most interesting reading. 

 Spallanzani, not content with making experiments on numerous animals 

 (frogs, birds, mammals, etc.) had the courage to carry out a great many 

 upon himself. He swallowed foods of various kinds and in various conditions 

 sewed in linen bags or inclosed in perforated wooden tubes which in turn 

 were covered with linen. The bags and tubes were subsequently passed 

 in the stools and were examined as to the amount and nature of their contents. 

 He seems to have experienced no injury from his experiments, although 

 normally his powers of digestion were quite feeble. As proof that the trit- 

 urating power of the stomach is not very great he calls attention to the fact 

 that some of the wooden tubes were made very thin, so that the slightest 



Eressure would crush them, and yet they were voided uninjured. So also 

 e found that cherries and grapes when swallowed whole, even if entirely 

 ripe, were usually passed unbroken. 



A better method of obtaining normal juice was suggested by the 

 famous observations of Beaumont* upon Alexis St. Martin. St. 

 Martin, by the premature discharge of his gun, was wounded in the 

 abdomen and stomach. On healing, a fistulous opening remained in 

 the abdominal wall, leading into the stomach, so that the contents 

 of the latter could be inspected. Beaumont made numerous inter- 

 esting and most valuable observations upon his patient. Since that 

 time it has become customary to make fistulous openings into the 

 stomachs of dogs whenever it is necessary to have the normal juice 

 for examination. A silver cannula is placed in the fistula, and 

 at any time the plug closing the cannula may be removed and 



* Beaumont, "The Physiology of Digestion," 1833; second edition, 1847. 

 For a biographical account of Beaumont, see Osier, "Journal of the American 

 Medical Association, " November 15, 1902. 





