On food and its digestion: being an introduction to dietetics . orms theconduit, and to that stream of secretion which it there-fore, at the period of greatest activity, has to convey. Its 74 DIGESTION. length, for reasons equally obvious, varies according tothe distance to which its orifice in the mouth is removedfrom the gland itself. But in spite of the great variationsthus permitted, the essential structure of all the salivaryglands is identical. Traced backwards from its terminalorifice, each has a duct, the thick wall of which perforatesthe mucous membrane by what is, in all but the smal
On food and its digestion: being an introduction to dietetics . orms theconduit, and to that stream of secretion which it there-fore, at the period of greatest activity, has to convey. Its 74 DIGESTION. length, for reasons equally obvious, varies according tothe distance to which its orifice in the mouth is removedfrom the gland itself. But in spite of the great variationsthus permitted, the essential structure of all the salivaryglands is identical. Traced backwards from its terminalorifice, each has a duct, the thick wall of which perforatesthe mucous membrane by what is, in all but the smallestspecimens, a tube formed of muscular and elastic this tube is enclosed a thin structureless membranelined by epithelial cells, possessing characters closely ap-proaching those of the cells of the mucous surface onwhich it opens. By repeated divisions, which are mostlybifurcations, the duct continually diminishes in its dia-meter as it increases in distance from its orifice, untilfinally its ultimate branches, reduced to a diameter of Fig. Diagram of two ducts of a lobule. {After Kocttiker.) a, Efferent duct of lobule ; bb, side branches; c, vesicles in situ; d, thesame separated, and the duct unfolded. about Y^th of an inch, suddenly expand into a numberof crypts of about 1£ times this size. The inner sur-face of the ramified duct is clothed with a flat polygonaltessellated epithelium of small size (^Vothincl1 dieter),forming but a single layer. (Fig. 3.) This cell-growth, SALIVARY GLANDS. 76 into which the larger coarser epithelium of the oral cavitymerges at a short distance from the commencement ofthe duct, is of exceedingly delicate structure, each of itsnucleated particles being exclusively occupied by a faintlygranular and albuminous liquid. A few allusions to the vascular supply, and to the mecha-nical arrangement, of these branched ducts may completethis brief notice of the structure of the salivary in areolar tissue (which here, as
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Keywords: ., bookauthorbrintonw, bookcentury1800, bookdecade1860, bookyear1861
