ACTIVITY OF THE WALL OF THE ALIMENTARY CANAL. 355 



ever, is but slight on account of the small endosmotic equivalent of the 

 salts to be absorbed. Salts are absorbed in larger amount from con- 

 centrated than from dilute solutions. If, however, considerable amounts 

 of salts with a high endosmotic equivalent are introduced into the in- 

 testine, as, for example, magnesium or sodium sulphate, these salts 

 retain the water for their solution, and in addition more fluid escapes 

 from the vessels of the intestinal wall, and diarrhea results. Conversely, 

 it is evident that, on injecting these substances into the blood, a large 

 amount of water passes from the intestine into the blood, so that con- 

 stipation results, in consequence of the great dryness of the interior of 

 the intestine. It should, however, especially be pointed out that the 

 absorption of solutions of various salts, isotonic with one another, 

 takes place differently. The epithelial cells of the intestine behave 

 like the erythrocytes with respect to the permeability of the solutions. 

 Water is absorbed from the stomach only in small amount. 



The absorption of fluids takes place best at moderate pressure within the 

 intestinal canal (from 80 to 140 cm. of water-pressure), in connection with which 

 the surface of the mucous membrane is best smoothed out. A greater degree of 

 pressure would compress the intestinal vessels and would accordingly allow 

 absorption to diminish. During digestion, on account of the dilatation of the 

 blood-vessels, absorption takes place rapidly. For this reason warm solutions 

 also are more quickly absorbed from the stomach than cold, the latter causing 

 contraction of the vessels. 



The fact that a 0.5 per cent, sodium-chlorid solution is better ab- 

 sorbed than water, further a potassium-solution less well than sodium- 

 solutions, and also the extensive absorption of dog's serum in the dog's 

 intestine, are opposed to the view that only physical forces (endosmosis) 

 are concerned in absorption. 



Some other inorganic substances also, which are not, as such, constituents of 

 the body, are absorbed by endosmosis: potassium iodid, potassium chlorate, 

 potassium bromid; further, iron-salts, as well as dilute sulphuric acid, etc. 



Carbohydrates in solution have their chief representatives in the 

 different varieties of sugar and principally in dextrose and maltose, 

 which have relatively high endosmotic equivalents, as cane-sugar is gen- 

 erally transformed by a ferment into invert-sugar. Absorption appears 

 to take place relatively slowly, as, at this time, only small amounts 

 of grape-sugar are found in the intestinal vessels and in the portal 

 vein. According to v. Mering, the sugar is absorbed from the intestine 

 by the portal vein. Dextrin is also present in the blood of the portal 

 vein, as boiling with dilute sulphuric acid increases the amount of sugar 

 in this blood. The amount of sugar absorbed depends upon the concen- 

 tration of its solution in the intestine. Therefore, the amount of sugar 

 contained in the blood is increased after a diet rich in sugar, so that 

 it may even pass over into the urine. To this end approximately a 

 0.6 per cent, solution of sugar in the blood is necessary. Also cane- 

 sugar in small amount has been found in the blood. When a large 

 amount of sugar-solution is present in the intestine, a portion also enters 

 the lymph- vessels. In a girl with a fistula of the receptaculum chyli, 

 not more than J per cent, of the sugar introduced into the alimentary 

 canal was found to be absorbed by the lacteals. The sugar is in part 

 consumed in the blood and in metabolism, perhaps principally in the 

 muscles. 



