. Chordate morphology. Morphology (Animals); Chordata. YOUNG MUCOUS GLAND SPENT MUCOUS GLAND MIXED GLAND Figure 8-14. Sections through various epidermal glands of Necturus. A, young mucous gland; B, spent mucous gland; C, poison gland; D, mixed mucous and poison gland. glandular and function along with the saccular mucous glands. In the salamander, the poison glands are nearly the same size as the mucous glands, but the lining of secretory cells is of a more irregular thickness and has clumps of nuclei. The granular contents of the gland is somewhat dif- ferent in appearance from that of the m
. Chordate morphology. Morphology (Animals); Chordata. YOUNG MUCOUS GLAND SPENT MUCOUS GLAND MIXED GLAND Figure 8-14. Sections through various epidermal glands of Necturus. A, young mucous gland; B, spent mucous gland; C, poison gland; D, mixed mucous and poison gland. glandular and function along with the saccular mucous glands. In the salamander, the poison glands are nearly the same size as the mucous glands, but the lining of secretory cells is of a more irregular thickness and has clumps of nuclei. The granular contents of the gland is somewhat dif- ferent in appearance from that of the mucous gland. The epidermis of Cryptobranchus is invaded by blood capillaries as a part of the respiratory fiinction of the skin. The skin of the Gymnophiona is thick and contains groups of dermal scales and large multicellular posion glands of a holocrine (entire cell breaks down) type (Figure 8-15). The epidermis of the early embryo is composed of an outer ciliated periderm and a deeper stratum germinativum. This condition persists up to a size of about 10 mm. when the epidermis, now somewhat thicker, loses the cilia and be- comes covered by a thin hyaline (clear) cuticula of secreted material similar to the basement membrane and the inter- cellular substance. Choanate fishes The skin of Latimeria is described as simple in structure. The epidermis is stratified and has a thick basement mem- brane. There are mucous cells and chromatocytes in the epidermis. The dermis is thick, fibrous and has many fat cells. In Protoplerus, a dipnoan, the epidermis is stratified with a basal, low columnar stratum germinativum and four or head calcified squomuia^. ayers of fibers basal pseudoepithelium outer columellar fibers basal fibrous layer (stratum compactum}' A B Figure 8-15. A, section through the skin of /chfhyophis g/uh'nosus showing glands and groups of scales enclosed in sacs. B, enlarged section of a scale showing the various layers. (After P. and F. Sorosin, 1887) 224 . THE SKIN AN
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