ABSORPTION OF NUTRIMENT. 129 



arid in that state are dispersed throughout the other constit- 

 uents of the chyme. But there are still some substances 

 undissolved, the presence of which therefore detracts from the 

 perfect character of chyme as a homogeneous substance : such 

 are the woody fibre from cell-walls, resinous matters, horny 

 and thick epidermic tissue. Some of these, being insoluble 

 in the alimentary canal, necessarily pass out with the alvine 

 excretion. 



The changes produced on the chyme in the duodenum by 

 the three agencies already referred to namely, the duodenal 

 secretion, the bile, and the pancreatic liquor have been made 

 as yet only in part. 



The acid of the chyme is certainly neutralised by the excess 

 of alkali contained probably in all the three just mentioned 

 agents, but certainly in the bile and the pancreatic juice. The 

 starch, if any remain, begins anew to be converted into sugar, 

 that process being suspended in the true stomach. The fatty 

 matters, probably by the joint action of all the three duodenal 

 agencies, is still further comminuted, and brought into that 

 state of fine division known as " emulsion ; " by which com- 

 plete division it seems to become admissible into the absorb- 

 ent vessels. Lastly, the albuminoid substances are still more 

 completely brought to the state of soluble albumen. 



Direct Absorption by the Blood -Vessels of the Mucous 

 Membrane. The earlier stages of the assimilation of the ali- 

 ment consist of processes of reduction and solution, so timed as 

 to adapt themselves specially to certain other arrangements of 

 the animal economy. The reduction and solution of the albu- 

 minoid portions of the food belongs in particular to the true 

 stomach ; and the suspension of the saccharin* cation of the 

 starch there has probably the effect of leaving the stomach 

 undisturbed in its proper function ; while the postponement 

 of the complete conversion of the starch into sugar and of the 



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