. A text-book of physiology : for medical students and physicians . ules, and thecells are again ready to form a secretion of normal should be borne in mind that in these experiments the glandswere stimulated beyond normal limits. Under ordinary conditionsthe cells are probably never depleted of their granular material tothe extent represented in the figures. In the cells of the mucous glands changes equally marked maybe observed after prolonged activity. In stained sections of the resting gland the cells arelarge and clear (Fig. 291),with flattened nucleiplaced well toward theb
. A text-book of physiology : for medical students and physicians . ules, and thecells are again ready to form a secretion of normal should be borne in mind that in these experiments the glandswere stimulated beyond normal limits. Under ordinary conditionsthe cells are probably never depleted of their granular material tothe extent represented in the figures. In the cells of the mucous glands changes equally marked maybe observed after prolonged activity. In stained sections of the resting gland the cells arelarge and clear (Fig. 291),with flattened nucleiplaced well toward thebase of the cell. Whenthe gland is made to se-crete the nuclei becomemore spherical and liemore toward the middleof the cell, and the cellsthemselves become dis-tinctly smaller. Afterprolonged secretion thechanges become moremarked (Fig. 292) and, according to Heidenhain, some of themucous cells may break down completely. According to mostof the later observers, however, the mucous cells do not actuallydisintegrate, but form again new material during the period of. Fig. 292.—Mucous gland: submaxillary ofdog after eight hours stimulation of the chordatympani. 762 PHYSIOLOGY OF DIGESTION AND SECRETION. rest, as in the case of the goblet cells of the intestine. In themucous as in the albuminous cells observations upon pieces ofthe fresh gland seem to give more reliable results than those uponpreserved specimens. Langley* has shown that in the freshmucous cells of the submaxillary gland numerous large granulesmay be discovered, about 125 to 250 to a cell. These granulesare comparable to those found in the goblet cells, and may beinterpreted as consisting of mucin or some preparatory materialfrom which mucin is formed. The granules are sensitive to re-agents; addition of water causes them to swell up and may be assumed that this happens during secretion, the gran-ules becoming converted to a mucin mass which is extruded fromthe cell. Action of Atropin, Pilocarpin, and
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