260 ABSORPTION OF THE FOOD. 



reducing the amount of arterial blood in that organ, which results 

 in an increased activity of the liver-cells, thereby causing an 

 excessive conversion of glycogen into sugar. This is one expla- 

 nation which has been given to account for the phenomenon. 

 Another is that the glycosuria is due to a direct action upon 

 the secretory nerves of the liver. 



(2) Phlorizin-dlabetes. Glycosuria may also be produced by the 

 administration of a number of different substances; among these 

 are phosphoric and lactic acids, strychnin, arsenic, phosphorus, 

 and especially phloridzin or phlorizin, a bitter substance, having 

 the chemical formula Cg^^O^, obtained from the bark of the 

 root of the apple-, pear-, and cherry-tree. Phlorizin is a glucosicl. 

 A glucosid is a vegetable principle which, when treated with 

 acids and some other substances, yields glucose and another sub- 

 stance which is characteristic of the particular plant from which 

 the glucosid was obtained. There are many glucosids which have 

 been isolated ; among these are, amygdalin, from bitter almonds ; 

 digitalin, from digitalis ; esculin, from the horse-chestnut, etc. It 

 was thought at one time that the glycosuria which follows the 

 administration of phlorizin was due to the glucose which it con- 

 tains, but it is now known that phloretin, which is a crystalline 

 substance formed by the action of an acid on phlorizin, and which 

 contains no glucose, will have the same effect as the phlorizin 

 itself. 



(3) A diabetic condition may also be produced by removing the 

 pancreas. Of this form of glycosuria we have already spoken 

 (p. 239). 



Absorption of Proteids. The theory that the digestion 

 of proteids consists in their being changed into a more diffusi- 

 ble form, and that in this condition they are absorbed by 

 the physical process of osmosis, has been to a considerable 

 degree abandoned. For while it is true that proteoses and 

 peptones are diffusible, while native albumins are not, still it has 

 been shown that egg-albumin is absorbed as such, although it 

 is non-diffusible. This absorption takes place in both the small 

 and large intestine ; in the former, under circumstaaces which 

 demonstrate that it could not have been previously peptonized, 

 and in the latter, of course, there is no peptonizing enzyme. We 

 must, therefore, attribute the absorption of proteids to the epithe- 

 lial cells, to whose efficiency in the process of absorption we have 

 so frequently had occasion to refer. Not only is egg-albumin 

 absorbed, but the same is true of syntonin as well. There is this 

 difference, however, that when egg-albumin is absorbed in such 

 quantity that it cannot be changed into an assimilable form while 

 passing through the cells of the villi, it is carried by the blood to 

 the kidneys, where it is eliminated, producing an "alimentary 

 alburninuria," while syntonin is utilized by the tissues. There 

 is little doubt that it is in the form of proteoses and peptones 



