ABSORPTION 849 



the carriers of the amino-acids which are formed in digestion ; 

 but, since it has been found possible to dialyse these from 

 the blood, the leucocytes must either break down in the 

 blood stream or give up the amino-acids before the tissues 

 are reached. 



(2) The amount of amino-acids is increased in the 

 blood. That they are absorbed by the blood-vessels and not 

 by the lymphatics is indicated by the fact that ligature of 

 the thoracic duct does not interfere with the absorption of 

 the nitrogen of the proteins. 



(8) The amino-acids are rapidly removed from the blood 

 by the tissues, and chiefly by the liver. Their concentration 



/ 



NONJ^WGENOUS 



Intestine 



Fig. 159. — To show the Splitting of the Amino-aeid Part of Proteins into a 

 nitrogenous part, which is changed to urea in the liver and excreted 

 by the kidneys, and into a non-nitrogenous part yielding sugar, which 

 is sent into the muscles. 



in this organ may be three or four times that of the blood. 

 Apparently, any surplus over that immediately required by 

 the tissues, accumulates in the liver and is so prevented 

 from exercising a toxic action on the heart. In the liver 

 the stored amino-acids are rapidly split up and the amidogen 

 portion converted to urea and excreted by the kidneys, 

 while the non-nitrogenous part is converted into carbo- 

 hydrates to a greater or less extent (fig. 159). The muscles 

 and other tissues accumulate these amino-acids to a much 

 smaller extent and hold them longer, probably for the 



