230 DIGESTION. 



rendering albumen assimilable; for Bernard found that, if 

 diluted egg-albumen, unmixed with gastric fluid, is injected 

 into the portal vein, it no longer makes its appearance in 

 the urine, and is, therefore, no doubt, assimilated by the blood. 



Probably, most of the albuminose, with other soluble and 

 fluid materials, is absorbed directly from the stomach by the 

 minute bloodvessels with which the mucous membrane is so 

 abundantly supplied. 



The saccharine including the amylaceous principles are at 

 first, probably, only mechanically separated from the vege- 

 table substances within which they are contained, by the 

 action of the gastric fluid. The soluble portions, viz., dextrin 

 and sugar, are probably at once absorbed. The insoluble 

 ones, viz., starch and lignin (or some parts of them), are ren- 

 dered soluble and capable of absorption, by being converted 

 into dextrin or grape-sugar. It is probable that this change 

 is carried on to some extent in the stomach ; but this conver- 

 sion of starch into sugar is effected, not by the gastric fluid, 

 but by the saliva introduced with the food, or subsequently 

 swallowed. The transformation of starch is continued in the 

 intestinal canal, as will be shown, by the secretion of the pan- 

 creas, and perhaps by that of the intestinal glands and mu- 

 cous membrane. The power of digesting uncooked starch is, 

 however, very limited in man and Carnivora, for when starch 

 has been taken raw, as in corn and rice, large quantities of 

 the granules are passed unaltered with the excrements. Cook- 

 ing, by expanding or bursting the envelopes of the granules, 

 renders their interior more amenable to the action of the di- 

 gestive organs ; and the abundant nutriment furnished by 

 bread, and the large proportion that is absorbed of the weight 

 consumed, afford proof of the completeness of their power to 

 make its starch soluble and prepare it for absorption. 



Of the oleaginous principles, as to their changes in the 

 stomach, no more can be said than that they appear to be 

 reduced to minute particles, and pass into the intestines min- 

 gled with the other constituents of the chyme. In the case 

 of the solid fats, this effect is probably produced by the sol- 

 vent action of the gastric juice on the areolar tissue, albumin- 

 ous cell -walls, &c., which enter into their composition, and by 

 the solution of which the true fat is able to mingle more uni- 

 formly with the other constituents of the chyme. Being fur- 

 ther changed in the intestinal canal, fat is rendered capable 

 of absorption by the lacteals. 



