DIGESTION IN THE STOMACH 



381 



characteristic secretion of the stomach. It is a matter of some 

 difficulty to obtain it pure; indeed, there is only one method 

 namely, that of making a gastric fistula. 



The older methods include (1) the giving of perforated hollow 

 balls of lead which contain food to birds of prey (the balls are sub- 

 sequently vomited up); (2) the swallowing of a sponge to which a 

 string is fastened, whereby it is subsequently withdrawn and squeezed ; 

 (3) killing of an animal after giving some indigestible material to eat, 

 and collecting the juice; (4) the withdrawal of the stomach-contents 

 by the passage of an oesophageal tube three-quarters of an hour after 

 a test-meal has been eaten. These methods give only gastric contents, 

 the mixed secretions plus the ingested food and fluid, and we gain 

 thereby no idea of what constitutes the true gastric juice. 



The first gastric fistula studied was one accidentally made by a 

 gunshot wound upon a Canadian, Alexis St. Martin. Beaumont took 



FIG. 196. PAWLOW'S METHOD OF ESTABLISHING A GASTRIC FISTULA. 



A, B, Incision; S, segment of stomach separated off; A, abdominal wall; e, mucous 

 membrane; P, pylorus; 0, oesophagus; Rv, right vjgus nerve; Lv, left vagus nerve. 



the man into his service, and published a small book, the result of 

 patient years of observation. A fistula has been established in dogs, 

 and observations made by several workers. A technique which leaves 

 intact the blood and nerve supply has been recent ly perfected 

 (see Fig. 196). 



In order that no food or saliva shall reach the stomach, an oesoph- 

 ageal fistula is made by bringing the oesophagus out to the side of 

 the neck, dividing it, and stitching both the upper and the lower end 

 into the wound, so as to leave the orifice of each patent. Any food 

 or saliva passing down the oesophagus falls out from the upper end, 

 and does not reach the stomach (sham feeding). Through the lower 

 opening substances can be introduced directly into the stomach. 

 The gastric juice obtained in this manner is a clean watery liquid; 

 its percentage composition varies in different animals. 



