. Physiology, experimental and descriptive . by Steapsin, an-other ferment of the pancreatic juice; they are decomposedwith the formation of free fatty acids, and thus more fullyprepared to be absorbed and to build up the tissues. Thesefree fatty acids aid in the work of emulsifying the rest of thefat. Saliva acts only on starch ; gastric juice, on proteids ; bile,on fats ; whereas pancreatic juice acts on all three, and prob-ably more energetically than the above-named liquids. The intestinal juice contains a ferment called Invertin,which changes cane sugar to dextrose, which is a variety ofg
. Physiology, experimental and descriptive . by Steapsin, an-other ferment of the pancreatic juice; they are decomposedwith the formation of free fatty acids, and thus more fullyprepared to be absorbed and to build up the tissues. Thesefree fatty acids aid in the work of emulsifying the rest of thefat. Saliva acts only on starch ; gastric juice, on proteids ; bile,on fats ; whereas pancreatic juice acts on all three, and prob-ably more energetically than the above-named liquids. The intestinal juice contains a ferment called Invertin,which changes cane sugar to dextrose, which is a variety ofgrape sugar. Dextrose is less soluble than cane sugar. Here,then, is an exceptional case, in which a digestive process con-verts a more solu-ble substance into aless soluble form. The bile and thepancreatic juice arealkaline, and over-come the acidity ofthe chyme. Absorption. —The mucous mem-brane of the small intestine is thrown into ridges ; but, unlikethose of the stomach, they run transversely. Openings of ^—Glands Intestinal Glands. Fig. 64. Mucous Membrane of Small Intestine. 220 ABSORP TION — 1 rILMI. Again, while the folds in the lining of the stomach aretemporary, these are permanent. They serve to increase thesurface of the lining, and to retard the passage of the foodmaterial, and so to aid the process of digestion and of absorp-tion. Further, the surface of the mucous membrane is thicklybeset with little cylindrical projections, like the pile on velvet. These pro-jections are calledVilli (singular, vil-lus). The villigreatly increasethe absorbing sur-face of the smallintestine. In eachvillus is a networkof Blood Capil-laries, and thebeginning oflymphatic capil-laries called Lac-teals. In the villithe largest partof the work ofabsorption isdone. The fatsare absorbed bythe lymph capil-laries, and the rest of the foods by the blood capillaries. Itshould be carefully noted that nearly all of the foods but thefats go at once to the liver, through the portal vein; bu
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