THE FOOD AND DIGESTION 333 



In swallowing fluids two sounds are heard, one immediately, 

 and one after about six seconds. 



III. Digestion in the Stomach. 



Various opportunities have occurred and have been taken 

 advantage of to study the interior of the human stomach 

 during life. The best known investigation of the kind was 

 undertaken by Dr. Beaumont, a Canadian physician, on the 

 person of St. Martin, a backwoodsman, who had received a 

 gunshot wound in the abdomen, which had left him with 

 an opening through the front wall of his stomach. Dr. 

 Beaumont engaged St. Martin as his servant, and made a 

 prolonged and valuable study of the changes which take 

 place in the viscus. 



He found that the condition varies greatly in fasting and 

 after feeding. 



A. Stomach during Fasting. 



The organ is collapsed, and the mucous membrane is 

 thrown into large ridges. It is pale in colour because the 

 blood vessels are not dilated. Movements are not marked 

 and the secretion is scanty, only a little mucus being formed 

 on the surface of the lining membrane. 



B. Stomach after Feeding. 



When food is taken, the blood vessels dilate, a secretion is 

 poured out, and movements of the organ become more 

 marked. 



1. Vascular Changes. The arterioles dilate, and the 

 mucous membrane becomes bright red in colour. This is 

 a reflex vaso-dilator effect, impulses, passing up the vagus 

 to the vaso-dilator centre in the medulla, and coming down 

 the vagus from that centre. Section of the vagi prevents 

 its onset. 



2. Secretion. (a) Characters of Gastric Juice. Very 

 rapidly a free flow of gastric juice occurs from all the glands 



