. Animal physiology. Physiology, Comparative; Physiology, Comparative. STRUCTURE OF GLANDS. 277 stomach (Fig. 77, <0, an(^ Pour tneir secretion separately into its cavity, having no communication with one another. The glan- dular apparatus which surrounds the alimentary canal in the Wheel-Animalcule (Fig. 59, /£, k) seems to be made up of similar follicles, having separate openings into the cavity. In more complex forms of the same organ, however, several follicles open together into a tube, which either pours its contents directly into the alimentary canal, or unites with other tubes to do
. Animal physiology. Physiology, Comparative; Physiology, Comparative. STRUCTURE OF GLANDS. 277 stomach (Fig. 77, <0, an(^ Pour tneir secretion separately into its cavity, having no communication with one another. The glan- dular apparatus which surrounds the alimentary canal in the Wheel-Animalcule (Fig. 59, /£, k) seems to be made up of similar follicles, having separate openings into the cavity. In more complex forms of the same organ, however, several follicles open together into a tube, which either pours its contents directly into the alimentary canal, or unites with other tubes to do so. The condition of such a glandular organ very much resembles that of a bunch of grapes; as is seen in Fig. 158, which re- presents the structure of the Parotid gland (one of the salivary glands) of Man. The main stalk is the duct into which all the others enter: from this pass off several branches, and these again give off smaller twigs, the extremities of which enter the minute follicles in which the secretion is formed. These follicles are lined, as in their simple condition, with cells, which are the essential instruments in the production of the secretion ; the fluid which they separate is poured, by the giving way of their walls, into the small canals proceeding from the follicles, thence into the larger branches, and finally into the main trunk, by which it is carried into the situation where it is to be employed or from which it is to pass out. The Liver will be seen to possess a structure exactly resembling this, in the Crustacea, by referring to Fig. 48 (fo) ; and in the Mollusca it is nearly the same (Figs. 14, /, and 142,/). 357. The required extent of secreting surface is not unfre- quently given, however, by the prolongation of the follicles into tubes, rather than by a great multiplication in their number. Of. Fig. 158.—Intimate Structure of a Composite Gland (the Parotid).. Please note that these images are extracted from scanned page images that may have
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