THE ABSORPTION OF THE FOOD-STUFFS 839 



quantitatively in the urine, and, as might be expected, does not 

 increase in any way the glycogen of the liver. When maltose is 

 injected in the same manner, a certain proportion of it is utilised 

 owing to the fact that the blood and fluids of the body contain a 

 ferment, maltase, capable of converting the disaccharide into the 

 monosaccharide, glucose. The absorption of these disaccharides 

 occurs therefore much more slowly from the intestine than does the 

 absorption of monosaccharides, the process of absorption being 

 always preceded by and waiting for the process of hydrolysis. Thus 

 huge doses of cane sugar may be taken without causing the appear- 

 ance of cane sugar in the blood or urine. It has been found that 

 sugar does not appear in the urine until as much as 320 grm. of cane 

 sugar have been ingested, whereas any quantity of glucose over 

 100 grm. may give rise to glycosuria. Lactose is absorbed still more 

 slowly, and in animals whose intestine is free from the ferment lactase, 

 is not absorbed ; large doses of lactose in such animals therefore give 

 rise to diarrhoea. The behaviour of the intestinal wall to the non- 

 assimilable sugars of artificial origin has not yet been sufficiently 

 investigated. It would be interesting to inquire whether the rate of 

 absorption of the different sugars was in any way determined by their 

 stereomeric configuration, whether, for instance, I- glucose would be 

 absorbed as rapidly as the ordinary ^-glucose. 



THE ABSORPTION OF PROTEINS 



In very few departments of physiology has there been so 

 great a revolution in our ideas as in that relating to protein 

 absorption, especially as to the form in which it is absorbed from 

 the alimentary canal, and its fate after absorption. As to the channel 

 by which it obtains entry into the circulation, practical agreement 

 reigns that it is absorbed by the blood-vessels. Almost every physio- 

 logist who has occupied himself with the investigation of the lymph 

 flow from the thoracic duct has been impressed by the fact that the 

 variations in the amount of lymph to be obtained in this way bear 

 no relation to the condition of the animal as regards the state of 

 digestion. Nor do we find any appreciable increase in the amount 

 of lymph flow or in the amount of proteins contained in this lymph 

 during digestion. The small increase observed by Asher and Barbera 

 would be sufficiently accounted for by the increased blood-supply 

 to the intestines during digestion, and is insufficient to account for 

 the absorption of any appreciable quantity of the protein which 

 is being taken up from the alimentary canal. Moreover it was 

 shown by Schmidt Mulheim that the absorption of proteins was not 

 interfered with as the result of ligature of the thoracic duct, and that 

 after this duct had been ligatured the ingestion of proteins was 



