146 PHYSIOLOGY. 



and the maltose into dextrose and laevulose. You do not find maltose 

 in the blood, notwithstanding large doses of it by the mouth, but 

 glucose. The carbohydrates not absorbed in the intestine, by the 

 action of bacteria undergo acid fermentation, forming acetic, lactic, 

 butyric, carbonic acids and hydrogen gas. Large quantities of 

 cane-sugar and milk-sugar generate acids which excite peristalsis 

 and cause a secretion of intestinal juice, which produces a diarrhoea 

 of frequent acid stools with a sour odor. The absorption of sugar 

 does not follow the laws of osmosis, but the columnar cells of the 

 epithelium must exert a peculiar activity, which temporarily may 

 be called vital, until we can explain it. If the blood is swimming 

 with sugar, then the kidneys secrete it, forming alimentary glyco- 

 suria. If more sugar arrives in the liver than its cells can take up 

 and change into glycogen, then the excess from the portal vein goes 

 into the hepatic vein and into the general circulation; and as the 

 muscles cannot localize and use it, it must pass out through the 

 kidneys. This is the assimilation limit for the various carbo- 

 hydrates, and it is different for the same individual. The assimila- 

 tion limit is higher for glucose and lower for milk-sugar. The blood- 

 vessels in the villi are the places of absorption of the carbohydrates ; 

 that is, the portal vein. 



Proteids. 



Albumins can be absorbed without being changed into proteoses 

 and peptones. Injections of soluble proteids into the vein are 

 assimilated, and they do not appear in the urine nor increase the 

 urinary nitrogen. Yet proteids are not absorbed as such in the pro- 

 cess of digestion, but are changed into albumoses and peptones. 

 Proteids were not absorbed by the lymph, for when about 100 grams 

 of proteid were eaten by a man, the lymph escaping by a fistula was 

 not increased in quantity, nor the amount of albumin in it aug- 

 mented. Although proteoses and peptones are absorbed by the por- 

 tal vein, they cannot be found in the blood. It might be supposed 

 that the liver changes them, but peptone injected into the portal 

 vein passes through the liver as such, lowers the blood-pressure, and 

 acts as a narcotic. Nor are the albumoses found in the lymph-chan- 

 nels of the intestine. Albumoses injected into the circulation reduce 

 the coagulability of the blood, lower the arterial tension, and act 

 like a poison. They are quickly excreted as such in the urine. 



Since during absorption of albumoses and peptones similar toxic 

 symptoms do not appear, it must be inferred that they are changed 





