EXCITANTS PRODUCED DURING DIGESTION. KM 



however, be very active, because after the psychic secretion, which lasts 

 two to three hours, comes to an end ; the hourly quantity of juice poured 

 out upon bread or egg-albumen is very small. Further, this statement 

 is supported by the following experiment. When a secretion is already 

 going on in the stomach, caused either by psychic effect or continued 

 from the last period of digestion, the unobserved introduction of fluid 

 egg-albumen, is always followed by a considerable augmentation of the 

 secretion (Dr. Chiyin). How is this phenomenon to be interpreted if one 

 is not to suppose that at the commencement of egg-white digestion a 

 body is formed which stimulates the mucous membrane ? The same 

 explanation which holds good for bread and egg-albumen may be 

 extended and applied to the proteids of flesh. Part of the chemical 

 exciting substance already exists in the meat ; the remainder, however, 

 is only formed during digestion. 



This investigation brings under our notice a very special and exceed- 

 ingly important property of the psychic or appetite juice. In the case of 

 flesh this juice affords important assistance to the pre-existing excitant, 

 and thereby determines a rapid digestion, shortening the stay of the 

 raw product in the digestive canal. With other foods for example, 

 with bread this juice is an indispensable condition to their digestion. 

 If bread or egg-albumen be eaten without appetite, or introduced 

 into the stomach unobserved, they lie there for a long time, just 

 as stones would lie, without the least appearance of digestion. In such 

 cases the appetite juice is the sole initiator of the secretory process and 

 the necessary condition for its continuation. If started by its assistance, 

 the digestion of these foods spontaneously proceeds. The psychic juice 

 here plays the role of the igniting material which sets the stove ablaze, 

 and for this reason it has been called " Igniting-juice " by Dr. Chigin. 

 Probably it is also, on this account, that the psychic juice with every 

 food possesses a uniform and tolerably strong digestive power. 



It is obvious that when bread or egg-albumen is eaten without appe- 

 tite ; water, or still better, meat broth or meat extract, may be made to 

 play the part of igniting material. I have been afforded an opportunity 

 of verifying all these results in actual practice, and in this way to test 

 whether our analysis of the secretory processes is correct. For the 

 delivery of these lectures I had to repeat my experiment on the influence 

 of vagus division on the secretory effect produced by sham feeding. 

 The result was that a greatly disordered condition of digestion was set 

 up in the dog, as I had anticipated from my own previous experience 

 and also from the publications of other authors, especially Ludwig and 

 Krehl. I resolved, in the light of our new discoveries, to try and aid 

 the animal's digestion. Now, in dogs with divided vagi, the psychic 

 secretion of gastric juice is wholly and for ever done away with. I 



