DIGESTION IN THE STOMACH 773 



THE EFFECT OF GASTRIC JUICE ON FATS 

 The chief action of this juice on fats is the solution of their con- 

 nective-tissue framework and protoplasmic envelopes, so as to set 

 the fat free in the stomach contents. After a fatty meal it is found 

 moreover that a considerable proportion of the fat in the stomach 

 has undergone hydrolysis and conversion into free fatty acid. In 

 this hydrolysis two factors are involved, viz. (1) the action of the 

 warm dilute hydrochloric acid ; (2) the action of a special fat- 

 splitting ferment or lipase, which is secreted by the walls of the 

 stomach, and acts especially at the beginning of gastric digestion 

 before the contents have attained a high degree of acidity. The 



c 



FIG. 334. Diagram to show Pawlow's method of making a cul-de-sac of the 



cardiac end of the stomach, with vascular and nerve supply intact. 

 In A the line of the incision into the stomach wall is shown. B represents 

 the operation as completed. In A : 0, oesophagus ; R.v, L.v, right and left 

 vagus nerves ; P, pylorus ; C, cardiac portion of stomach ; A, B, line of 

 incision. In B : F, main portion of stomach ; S, cardiac cul-de-sac ; A, 

 abdominal wall ; e, e, mucous membrane reflected to form diaphragm between 

 the two cavities. 



action of this ferment is only marked if the fat be present in a finely 

 divided form, e.g. as yolk of egg. The chief digestion of fat takes 

 place in the next segment of the alimentary canal, namely, in the 

 duodenum. 



THE SECRETION OF GASTRIC JUICE 



Pawlow has shown that if an animal provided with gastric and 

 oesophageal fistula be given food, when hungry, it will eat with 

 avidity, and since the food cannot reach tbe stomach and so satisfy 

 its hunger, it will continue to eat for two or three hours. Five 

 minutes after the beginning of this sham feeding, gastric juice begins 

 to drop from the fistulous opening ; and in this way large quantities 

 of juice, free from any admixture with other substances, can be easily 

 obtained. By this means we obtain a secretion of gastric juice, which 



