508 LECTURE XXI. 



corresponds evidently to the time required by the alkaline juices of the 

 intestine to neutralize the hydrochloric acid in the chyme. When this 

 has been effected, then, reflexively, the pylorus is opened and a new 

 portion of chyme passes out of the stomach. The suitability of such 

 an arrangement is quite obvious. We shall see that the ferments of the 

 pancreas can act only in neutral or alkaline solutions. If now the entire 

 acid contents of the stomach were to be suddenly emptied into the intes- 

 tines, then evidently the subsequent digestion would suffer. 1 In fact, only 

 moderate amounts of chyme are to be found in the intestines of animals 

 killed at various times after an abundant feeding. This is particularly 

 remarkable when we compare the contents of the tightly stretched stomach 

 at the beginning of digestion with that of the duodenum. The small 

 portions of chyme as they leave the stomach are evidently at once further 

 digested and absorbed. To the fat, also, has been ascribed an effect on 

 the opening and closing of the pylorus. Enough has been said to show 

 that the emptying of the stomach may take place with different degrees 

 of rapidity according to the prevailing conditions. On the other hand, it 

 enables us to understand why such contradictory statements are found 

 in the literature concerning the time required. Almost all of the early 

 investigators followed the course of the stomach's activity, by means of a 

 fistula in the duodenum, in such a way that the chyme on leaving the 

 stomach, in part at least, passed at once through the fistula opening, 

 whereby naturally quite unusual conditions were created, leading to quite 

 uncontrollable changes in the natural processes. 



A question which has been much discussed is whether absorption 

 begins to take place in the stomach. At present we can only answer this 

 question in so far as we know that it is certain that the mucous membrane 

 of the stomach does take up certain substances from the chyme. As soon 

 as we possess further information concerning the amount and nature of 

 the absorbed substances, we shall be able to close up this gap in our 

 knowledge. Pure water is not absorbed perceptibly; but, on the other 

 hand, aqueous solutions of sugar and peptone and of salts lose part of the 

 dissolved substance, and part of the water while they are in the stomach. 

 The absorption of digested albumin in the stomach has been studied par- 

 ticularly carefully, but without its being possible to get any clear idea as 

 to the extent that this takes place. We shall come back to this question 

 of absorption when we speak of the functions of the remaining parts of the 

 alimentary canal. We may, however, state in advance that it has not 

 yet been found possible to refer these processes completely to physical or 

 chemical laws. 



1 This fact must be considered in cases where there is an excessive secretion of 

 gastric juice, and especially of hydrochloric acid. This tends to increase the time 

 required by the stomach to empty itself. 



