468 



DIGESTION 



(1729-1799) attacked this problem by methods that anticipated those of Behfuss and 

 Einhorn. Spallanzani ultimately devised the method of swallowing small perforated 

 wooden tubes containing foodstuffs and covered by small linen bags. After the bags 

 were passed per rectum, he found that considerable erosion or digestion of the food 

 had occurred, but that the wooden tubes, however thin-walled they might be, were 

 not crushed. In order to secure samples of the gastric juice free from food, the 

 only method available to the older investigators consisted in swallowing sponges at- 

 tached to threads, which after being for some time in the stomach were withdrawn 

 and squeezed dry of juice. 



The next great contribution came from this country, where, in 1833, Dr. Beaumont, 

 while a surgeon in the service of the American troops located at Mackinaw, made ob- 

 servations on a Canadian voyageur by the name of Alexis St. Martin, who by the 

 premature discharge of his gun had wounded himself in the stomach, the wound never 

 healing but leaving a permanent gastric fistula. Beaumont arranged to keep Alexis St. 

 Martin in his service for several years, during which time he made numerous observa- 



Fig. 148. Diagram of stomach showing miniature stomach (5) separated from the main stomach 

 (V) by a double layer of mucous membrane. A.A., is the opening of the pouch on the abdominal 

 wall. (Pavlov.) 



tions on the process of digestion in the stomach observations many of which are of 

 great value even at the present day. 



By none of these methods, however, could a sample of pure gastric juice be secured 

 while the digestive process was actually in progress. To make the collection of such a 

 sample possible, Heidenhain devised a method of isolating portions of the stomach wall 

 as pouches opening through iistulse on the abdominal wall. The results of Heidenhain 's 

 experiments are, however, open to the objection that the secretion in the isolated 

 pouches may not really correspond to that occurring in the main stomach, since the 

 connections of the pouches with the central nervous system must have been severed. 

 In order that these connections might remain as nearly intact as possible, the Russian 

 physiologist, Pavlov, 1 devised an ingenious operation in which the pouch, or " minia- 

 ture stomach," remains connected with the main stomach through a considerable width 

 of mucous and submucous tissue and in which the nervous connections are not severed. 

 The essential nature of this operation will be evident from the accompanying diagram. 

 (Fig. 148.) 



