86 THE HUMAN BODY. 



the duodenum through the pyloric orifice, the bile and the 

 pancreatic juice mingle with it, as the gastric juice does in 

 the stomach. They both aid in liquefying the chyme by the 

 water which they contain, and by their special action upon 

 the substances of which it is composed: the pancreatic juice 

 continues with even more activity than the saliva to trans- 

 form the amylaceous matter into glycose. The bile assists 

 the digestion of the animal matter by reducing the fatty 

 bodies to an emulsion, and it appears also to act as an 

 excitant to the function of the intestine; and lastly, a fluid 

 secreted by the mucous membrane of the intestine, as the 

 gastric juice is by the stomach, co-operates with the biliary 

 and pancreatic secretions. Under the influence of these 

 agents, of the fermentation induced by the pepsine and of 

 the peristaltic movement, the chyme is liquefied during its 

 advance through the smaller intestine, and is transformed 

 into a white milky fluid the chyle which the chyliferous 

 vessels draw from the surface of the mucous membrane, and 

 carry to the thoracic duct, from whence it goes to be mixed 

 with the blood. 



Absorption. The moment chyle is formed .digestion proper 

 may be considered as accomplished, though on this function 

 also depends the absorption of the chyle, which must still be 

 perfected in its course through the smaller intestine and the 

 veins before it mingles with the blood. 



The mechanism of absorption is still unknown. It has been 

 explained as taking place by endosmosis a phenomenon dis- 

 covered by Dutrochet, which results from the property which 

 tissues possess, under certain conditions, of permitting fluid 

 or gaseous bodies to pass through their capillary canals. If, 

 for example, two fluids which may be mixed, though they 

 may be of different natures and different densities, are separ- 

 ated by a membrane, two currents are established through 

 this membrane in opposite directions, and of unequal force, 

 tending to mix the two fluids, the stronger current is gener- 

 ally produced by the fluid the least dense; and this is called 

 endosmosis the feebler current exosmosis. In this experi- 

 ment the substances mingle without changing their nature; 

 but it is not so in absorption. The substances absorbed by 



