GASTRIC SECRETION AND DIGESTION 87 



of starch and protein respectively are subdivided pro- 

 gressively, first with the formation of somewhat complex 

 bodies dextrins and proteoses later to form maltose in 

 the first instance and peptones in the second. The corre- 

 spondence is imperfect in several ways; for example, mal- 

 tose is a single substance, while there appear to be a number 

 of peptones. It will be remembered that maltose itself 

 is slowly transformed by long-continued action of saliva. 

 Quite similarly, the gastric juice will in time effect a fur- 

 ther digestion of the peptones, but this advanced diges- 

 tion seems normally to be postponed until the intestine is 

 reached. 



Gastric Lipase. Down to a recent time it was held that 

 fat underwent no true digestion in the stomach. It was 

 recognized that some forms of fat, butter, for example, 

 must be melted, and that the fat in the adipose tissue of 

 meat might be released from the enclosing cells when their 

 protein portion was dissolved. These, however, are mere 

 physical changes. Attentive study has brought out the 

 fact that there is, after all, some hydrolysis of fat in the 

 stomach, though it is probably slight. An enzyme with 

 this action is accordingly assumed and is spoken of as 

 gastric lipase. It is only the most finely divided (emulsi- 

 fied) fats which seem to be appreciably affected. The 

 products of this decomposition as well as of the later fat 

 digestion in the intestine are glycerin and free fatty acids. 



Summary. The material passing the pylorus is com- 

 paratively dilute and normally free from coarse particles. 

 It is acid in reaction, both the native hydrochloric acid and 

 the acids formed by fermentation contributing. Much 

 of the food is as yet practically undigested. On the other 

 hand, some progress has been made in the transformation 

 of cooked starch into sugar. The proteins are partially 

 peptonized. If milk has formed a part of the diet, it will 

 have been curdled and redissolved. Fats may have been 

 liquefied and scattered, but are not likely to have been 

 extensively hydrolyzed. On the whole, gastric digestion 

 may fairly be described as preliminary in character. 



