298 ABSORPTION OF SOLUBLE CARBOHYDRATES. 



the intestinal vessels into the intestine. The amount of water, however, is small, 

 owing to the small endosmotic equivalent of the salts to be absorbed. More salts 

 are absorbed from concentrated than from dilute solutions. If large quantities of 

 salt, with a high endosmotic equivalent, e.g., magnesium or sodium sulphate, are 

 introduced* into the intestine, these salts retain the water necessary for their solu- 

 tion, and may thus cause diarrhoea. Conversely, when these substances are injected 

 into the blood, a large quantity of water passes from the intestine into the blood, 

 so that constipation occurs, owing to dryness of the intestinal contents (Aubert). 



[M. Hay concludes from his experiments ( 161), that salts, when placed in the intestines, 

 do not abstract water from the blood, or are themselves absorbed, in virtue of an endosmotic 

 relation being established between the blood and the saline solution in the intestines. Absorp- 

 tion is probably due to the filtration and diffusion, or processes of inhibition other than endos- 

 mosis, as yet little understood. The result obtained by Aubert, which is not constant, is mostly 

 caused by the great diuresis which the injected salt excites.] The absorption of fluids takes 

 place best at a medium pressure of 80 to 140 c.cm. of water within the intestine ; higher pressure 

 compresses the blood-vessels and diminishes the absorption. During digestion, owing to the 

 dilatation of the vessels, absorption is more rapid. The fact that 0"5 per cent, solution of NaCl 

 is absorbed better than water, and soda solution than potash solution, seems to show that 

 physical forces are not the only factors concerned. 



Numerous inorganic substances, which do not occur in the body, are absorbed by endosraosis 

 from the intestine, e.g., dilute sulphuric acid, potassium iodide, chlorate, and bromide, and 

 many other salts. 



(2) The soluble carbohydrates, such as the sugars, of which the chief repre- 

 sentatives are dextrose and maltose, with a relatively high endosmotic equivalent. 

 Cane-sugar is changed by a special ferment into invert-sugar ( 183, 5). Absorption 

 appears to take place somewhat slowly, as only very small quantities of grape-sugar 

 are found in the chyle vessels, or the portal vein, at any time. According to v. 

 Mering, the sugar passes from the intestine into the rootlets of the portal vein ; 

 dextrin also occurs in the portal vein. When the blood of the portal vein is boiled 

 with dilute sulphuric acid, the amount of sugar is increased. The amount of sugar 

 absorbed depends upon the concentration of its solution in the intestine ; hence the 

 amount of sugar in the blood is increased after a diet containing much of this sub- 

 stance, so that it may appear in the urine ; in which case the blood must contain at 

 least 0*6 per cent, of sugar. A small amount of cane-sugar has also been 

 found in the blood (CI. Bernard). The sugar is used up in the bodily metabolism ; 

 some of it is perhaps oxidised in the muscles ( 176). 



(3) The peptones have a small endosmotic equivalent, a 2 to 9 per cent, solution 

 = 7 to 10. Owing to their great diffusibility they are readily absorbed, and they 

 are the chief representatives of the proteids which are absorbed. The amount 

 absorbed depends upon the concentration of their solution in the intestine. When 

 animals are fed on peptones (with the necessary fat or sugar), they serve to maintain 

 the body- weight. [According to P16sz and Gyorgyai, Drosdorff and Schmidt- 

 Mulheim, peptones occur only in traces in the blood of the portal vein. Neumeister, 

 however, using the best methods, finds that although peptones are abundant in the 

 intestine, not a trace of peptone or of the albumoses is found either in the blood or 

 lymph. This coincides with Hofmeister's researches, and is of course opposed to 

 the results of the above-named observers. As no peptones or albumoses have been 

 found in the blood, and as they can compensate for the total metabolism of the 

 proteids within the body, we must assume that they are rapidly converted into 

 true albuminous bodies.] Hofmeister supposes that the leucocytes absorb the 

 peptones and act as their carriers, much as the red corpuscles are oxygen carriers. 

 They carry the peptones into the mucous membrane of the stomach and small 

 intestine, which are very rich in peptone at the fourth hour of digestion. [The 

 number of leucocytes is greatly increased in the mucous membrane, especially in 

 the stomach and upper part of the duodenum, during digestion, and diminished 

 during fasting in dogs and cats. The same is the case with the lymph-follicles, the 



