The epithelium, e, is of the stratified squamous variety, but consists of many more layers of cells than in the preceding section and is hence several times as thick. While its cells are flattened towards the surface, after the manner of this kind of epithelium, they do not form the definite horny layer described above.
Fig. 38. One of the glands from the posterior region of the tongue of the hibernating animal, under high magnification; a, areolar tissue; av, alveolus.
The most marked difference between the two regions of the tongue is the presence, in the posterior or basal region, of numerous glands, g, probably mucous- or slime-secreting. They are thickly scattered through the areolar base, close beneath the epithelium. Two large glands and one small one are shown in the figure under discussion. Each gland opens to the surface by an apparently wide duct, but since no good section of such a duct was obtained it is not shown in the figure. Although the rest of the tissue was well preserved and showed cell structure clearly, it was with difficulty that the details of the glands could be determined.
A high-power drawing of a portion of one of the glands is shown in [Figure 38]. The large alveolus, av, to the left, is from the peripheral region of the gland and is surrounded, on its free side, by the areolar tissue described above. The inter-alveolar spaces, which are somewhat exaggerated in the figure, are filled with fibers which are arranged more or less in layers and hence appears different from the surrounding areolar tissue. The alveoli are circular or elongated in section, and have fairly wide lumina. They are lined with a single layer of columnar or cuboidal cells which are very granular, so that their walls are difficult to determine. Each cell contains, near its base, a very large, usually spherical nucleus. These nuclei stain darkly and give the dark appearance to the glands as seen under low magnification, especially in rather thick sections.
During feeding the epithelium of this region of the tongue consists of fewer layers of cells than during hibernation but is otherwise unchanged from what is described above. The glands consist, at least in all of the material examined, of much fewer alveoli than are shown in [Figure 37]. One of these glands is shown in [Figure 39].
Although no more care was used in fixation than in the corresponding tissue of the hibernating animal the glands here show their cell details far more clearly than in the former tissue; this may have been partly due to the latter sections being thinner.
The glands are of a compound, tubulo-alveolar type; although numerous sections through ducts were obtained (as in [Fig. 39]), no details of these ducts could be seen.
Fig. 39. One of the glands from the posterior region of the tongue of the feeding animal, under somewhat higher magnification than used in [Figure 37]; av, alveolus; d, duct of gland; e, stratified epithelium.