. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. STOMACH AND INTESTINE. 355 which immediately succeeds death. And their duration is rarely protracted beyond a few minutes. C/ianges in the vlIH during digestion. — Dur- ing the act of digestion, the vilii undergo cer- tain noticeable alterations. At this period, they receive an increased afflux of blood ; and become both larger and softer. They ac- quire a greater opacity ; so as to appear whiter by reflected, and darker by transmitted, light. The nuclei and cells which occupy their in- terior are greatly increased in nu
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. STOMACH AND INTESTINE. 355 which immediately succeeds death. And their duration is rarely protracted beyond a few minutes. C/ianges in the vlIH during digestion. — Dur- ing the act of digestion, the vilii undergo cer- tain noticeable alterations. At this period, they receive an increased afflux of blood ; and become both larger and softer. They ac- quire a greater opacity ; so as to appear whiter by reflected, and darker by transmitted, light. The nuclei and cells which occupy their in- terior are greatly increased in number and dis- tinctness. And, finally, after the ingestion of food containing the usual fatty ingredients, a portion of these may be found occupying the interior of the vilii themselves. The process by which fatty matter pene- trates the villus to enter the lacteal in its centre, deserves our special attention, from the fact that it constitutes the origin of the chyle. At present we shall limit ourselves to a description of the appearances actually observed, in connection with the mucous membrane of the alimentary canal. The first step towards the absorption of the fatty matter, consists in its entry into the epithelium which invests the exterior of the villus. Each columnar cell of this covering is gradually filled by a large oil globule ; which occupies the whole of its cavity, with the ex- ception of that small portion devoted to its nucleus. This change first implicates a few scattered epithelia; and, by rendering them Fig. Til'us of the dog about two hours after feeding : show- inq the entry of fatty into scattered epithelia on its surface. Magnified about 4UO diameters. a, a, outline of the villus formed by epithelia with their ordinary contents; ft, ft, epithelia rendered bright and re'fractile by their fatty contents. more refractile, often causes various parts of the surface of the villus to offer a curious con- trast of bright spots (b,Jig. 26-3.) and darker
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