BIGBSTION OP FOOD. 299 



Grastric Juice. — Gastric juice may be obtained from a fistu- 

 lous opening into the stomach. Such may be made artificially 

 by an incision over the organ in the middle line, catching it up 

 and stitching it to the edges of the wound, incising and insert- 

 ing a special form of cannula, which may be closed or opened 

 at will. 



Digestion iu a few cases of accidental gastric fistulas has 

 been made the subject of careful study. The most instructive 

 case is that of Alexis St. Martin, a French Canadian, into 

 whose stomach a considerable opening was made by a gunshot- 

 wound. 



Gastric juice, in his case and in the lower animals with 

 artificial openings in the stomach, has been obtained by irri- 

 tating the mucous lining mechanically with a foreign body, as 

 a feather. 



The great difficulty in all such cases arises from the impos- 

 sibility of being certain that such fluid is normal ; for the con- 

 ditions which call forth secretion are certainly such as the 

 stomach never experiences in the ordinary course of events, 

 and we have seen how saliva varies, according as the animal is 

 fasting or feeding, etc. 



Bearing in mind, then, that our knowledge is possibly only 

 approximately correct, we may state what is known of the se- 

 cretions of the stomach. 



The gastric secretion is clear, colorless, of low specific grav- 

 ity (1001 to 1010), the solids being in great part made up of 

 pepsin with a small quantity of mucus, which may become ex- 

 cessive in disordered conditions. There has been a good deal 

 of dispute as to the acid found in the stomach during digestion. 

 It is now generally agreed that during the greater part of the 

 digestive process there is free hydrochloric acid to the extent 

 of about -3 per cent It is maintained that lactic acid exists 

 normally in the early stages of digestion, and it is conceded that 

 lacj;ic, butyric, acetic, and other acids may be present in certain 

 forms of disordered digestion. 



It is also generally acknowledged that in mammals the work 

 of the stomach is limited, so far as actual chemical changes go, 

 to the conversion of the proteid constituents of food into pep- 

 tone. Fats maybe released from their proteid coverings (cells), 

 but neither they nor starches are in the least altered chemically. 

 Some have thought that in the dog there is a slight digestion of 

 fats in the stomach. The solvent power of the gastric juice is 



