. Elementary biology; an introduction to the science of life. Biology. DIGESTIVE SYSTEM IN MAN 87 "'J'lS I Blaihicr Liver chemical changes in the gut. There is a ferment in the intestinal juice which converts cane sugar into simpler sugars, but this chan-e may also be brought about by the acids of the stomach, and possibly also by the alkali in the intestine. 123. Absorp- tion. The lin- ing of the small intestine is like delicate velvet. Very small out- growths project into the cavity, so that the sur- face exposed to contact with the food mixture is increased sev- eral hundred times. Eac
. Elementary biology; an introduction to the science of life. Biology. DIGESTIVE SYSTEM IN MAN 87 "'J'lS I Blaihicr Liver chemical changes in the gut. There is a ferment in the intestinal juice which converts cane sugar into simpler sugars, but this chan-e may also be brought about by the acids of the stomach, and possibly also by the alkali in the intestine. 123. Absorp- tion. The lin- ing of the small intestine is like delicate velvet. Very small out- growths project into the cavity, so that the sur- face exposed to contact with the food mixture is increased sev- eral hundred times. Each of these tiny pro- jections, called a villus (plural, villi), has a rather complex structure, as is shown in the di- agram (Fig. 31). The villus seems to be a special absorbing and transforming organ. The mixture in the intestine we now know to' consist o'f many crystalloids in solution, many colloids in the process of being converted into crystalloids, and solid substances that are not capable of changing under the conditions that exist in the gut. The crystalloids are absorbed into the cells of the villi, so that as the mass moves along in the intestine, more and more. Intesline Rectum Fig. 32. Digestive system in fish and in bird The main features of the digestive system are alike in all back- boned animals. In the birds there is a curious pouch connected with the gullet, — the crop, — in which food may be retained in- definitely and later either swallowed or regurgitated through the mouth. The glandular portion of the stomach, or proventriculus, is distinct from the grinding part, or gizzard. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gruenberg, Benjamin C. (Benjamin Charles), 1875-1965. Boston New York [etc. ] Ginn and company
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