GASTEIC DIGESTION. 341 



about three minutes. The inhibitory action of the splanchnics in the 

 thorax is less marked than the motor action of the vagi; the inhibitory 

 power of the left splanchnic is greater than that of the right. „ 



It thus would appear that the circular muscular fibres of the pyloric 

 ring are innervated bj r two antagonistic sets of nerves, the vagus being 

 the motor nerve and the splanchnic the inhibitory nerve. 



When the food is received in the stomach it is gradually dissolved, 

 and we have, therefore, to stud}- the several processes which are concerned 

 in this action. The general outline of the characters of that change will 

 first be given, then the properties of the secretion to whose action it is 

 due, the action of this secretion on the various food-stuffs, the nature of 

 the resulting products, the conditions essential to gastric digestion, and, 

 finally, the mode in which the gastric juice is secreted. 



The study of gastric digestion is especially a study of chemical 

 changes. It was seen that in the mouth the food was not only subjected 

 to the chemical changes produced by the saliva, but that through 

 mechanical changes resulting from mastication and the close mixing of 

 the food with the saliva the materials destined to nourish the body were 

 brought into the most favorable conditions for subjection to the various 

 solvent juices of the economy. The first and the most important of these 

 with which the food comes in contact in its onward passage through the 

 alimentary canal is the gastric juice. In the experiments made on the 

 saliva the precedent was established of performing acts of digestion, or 

 at least acts introductory to digestion, outside the body, the natural 

 conditions being preserved as far as possible. In the study of gastric 

 digestion it will be found that this step is not unwarranted. All the 

 phenomena of gastric digestion may be as completely and conveniently 

 studied in an artificial stomach as in the living organ, a fact demonstrative 

 of the essentially chemical nature of the process. 



Xot only may such experiments be conducted outside of the body, 

 but they may even be performed with artificial gastric juice. 



Such a fluid, or artificial gastric juice, of considerable purity may be obtained 

 by mincing the mucous membrane of the stomach of almost any animal, drying 

 the fragments between layers of filter-paper, and allowing them to remain for 

 twenty-four hours under absolute alcohol. They are then removed from the 

 alcohol and covered with strong glycerin. In a few days the glycerin will 

 become strongly impregnated with pepsin, the ferment of the gastric juice, and 

 may be preserved for almost any length of time The addition of a few drops of 

 this glycerin extract to one hundred cubic centimeters of hydrochloric acid of 

 .02 per cent: will produce a fluid of high digestive power, and one which is quite 

 permanent. 



An artificial gastric juice may also be obtained by rubbing up the minced 

 mucous membrane of the stomach, from which the mucus has been removed by 

 gentle scraping-, in a mortar with clean sand or powdered glass and water. It 

 should then stand for some hours, being occasionally stirred, and finally filtered. 

 The filtrate will contain pepsin and a small amount of peptones. Added to an 

 equal bulk of .03 per cent, of hydrochloric acid, it will form a powerful digestive 

 fluid, which maybe kept for a long time, not even losing its powers when mouldy. 



