264 PHYSIOLOGY CHAP. 



and agminated follicles and by the lymph glands interposed along 

 the lacteals. The chyle poured out (with the lymph) into the 

 left subclavian vein contains a comparatively small proportion of 

 the total of the food-stuffs elaborated by the secreting and absorbing 

 cells of the gastro-intestinal mucous membrane, and destined to 

 compensate the tissues for their losses. 



The title Internal Eestitutive Secretions given to this chapter 

 comprises the study of all those complex processes by which 

 the individual groups of food-stuffs (which may or may not 

 have suffered the chemical metamorphoses of digestion discussed 

 in the two preceding chapters) are absorbed, partially regenerated, 

 secreted into the lymph spaces of the rnucosa, carried away by the 

 lacteals and venous portal system, stored up in the various organs, 

 tissues, and cells as reserve materials, and finally poured out or 

 secreted into the blood, to compensate for the losses caused by 

 assimilation and the functional work of the tissues. 



I. The Mucous Membrane of the entire tract of the alimentary 

 canal, from mouth to anus, forms, on account of the epithelium 

 which covers it, a single, extended, absorbing surface. But the 

 mouth, pharynx, and oesophagus, owing to the thickness of the 

 stratified epithelium, and to the fact that the food does not remain 

 long enough in them to undergo any important chemical digestive 

 modifications, play no perceptible part in absorption, although 

 certain intoxications prove that they are capable of it. 



On the other hand, it is well known that the stomacli does 

 play an active part in absorption. The simplest demonstration 

 of the fact is the rapidity with which certain poisons take effect, 

 particularly after the introduction of toxic substances in alcoholic 

 solution. Another obvious proof of absorption in the stomach is 

 seen in sections from animals killed during digestion, in which 

 the lymphatics of the stomach are found to be congested. 



Von Mering (1893) published results of his accurate observa- 

 tions on the absorptive functions of the gastric mucous membrane, 

 which are important from both a hygienic and a clinical stand- 

 point. His method consisted in establishing a duodenal fistula on 

 dogs, and then introducing into the stomach a given amount of 

 fluids or watery solutions of various foods, after which the outflow 

 from the fistula was collected, measured, and analysed at con- 

 secutive intervals. 



If the animals were allowed to drink plain water freely, it 

 spurted in a short time from the fistula in jets that recurred 2-6 

 times per minute ; 2-15 c.c. of water were excreted at each jet. 

 Von Mering ascertained by over 100 tests that the quantity of 

 fluid escaping from the fistula was approximately equal to that 

 introduced, and might even be larger, owing perhaps to the 

 saliva that became mixed with it during deglutition. He con- 

 cluded that water was not absorbed by the stomach in any 



