DIGESTION OF THE CARBOHYDRATES. 167 



are likewise capable not only of causing the transformation of disac- 

 charides into monosaccharides, but also of inverting dextrin to 

 maltose. It has been shown that in animals with Thiry-Vella 

 fistulae injected solutions of starch and cane-sugar rapidly disappear, 

 although maltose cannot at times be demonstrated in the fluid. In 

 what manner this change is effected by the epithelial cells is not 

 known. In any event, however, it is necessary that the polysac- 

 charides should be inverted to monosaccharides before passing beyond 

 the mucous membrane of the gastro-intestinal tract. Resorption 

 takes place primarily through the specific activity of the epithelial 

 lining of the gastro-intestinal mucosa. The monosaccharides then 

 enter the blood-current and are carried to the muscles and the liver, 

 where they are transformed into glycogen and stored in a manner 

 analogous to the reserve starch of the plant. This transformation, 

 however, as well as the subsequent fate of the sugar, we shall have 

 occasion to study in greater detail in a subsequent chapter. 



Neither the poly sacchar ides nor the disaccharides when introduced 

 into the blood-current directly can be utilized by the body as such, 

 and they are accordingly eliminated in the urine as foreign matter. 



The extent to which amylolysis can occur in the intestinal canal 

 is remarkable, and far exceeds the ability of the liver and the muscle- 

 tissue to transform the corresponding amount of monosaccharides 

 into glycogen. As a consequence, the percentage of circulating 

 sugar rises beyond the normal and glucosuria results. That disac- 

 charides may pass the intestinal mucosa without being inverted is 

 possible, but is certainly of exceptional occurrence. In such cases 

 we must imagine that the intestinal epithelium has lost its specific 

 power as a barrier to the passage of the sugars, as well as its ability 

 to cause their inversion. As a result they pass this barrier by diffu- 

 sion, and probably enter both the blood- and the lymph-current, and 

 are then eliminated in the urine. A formation of glycogen from di- 

 saccharides directly is apparently not possible. 



The rapidity with which resorption takes place in the small intes- 

 tine seems to vary with the character of the sugar. In dogs Alber- 

 tini thus found that of 100 grammes of glucose, 60 grammes are 

 absorbed in the course of the first hour, while of maltose and cane- 

 sugar from 70 to 80 grammes and of lactose only 20 to 40 grammes 

 disappear within the same period of time. 



The ingestion of very large amounts of disaccharides and mono- 

 saccharides leads to a general disturbance of intestinal digestion and 

 results in diarrhoea. A corresponding amount of starch, on the 

 other hand, is without effect in this respect. This is no doubt owing 

 to the fact that in the latter case inversion and resorption proceed 

 paripassu, so that the bacteria have but little chance of setting up 

 fermentative changes, which lead to the formation of substances 

 that directly increase the peristalsis owing to their irritating prop- 

 erties. In the presence of abnormally large amounts of sugars as 

 such, on the other hand, resorption is not sufficiently rapid, and in 



