. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 210 Biology of the Vertebrates rant fishes, is an interwoven network of vertical and horizontal connective tissue fibers, practically undifferentiated into strata. 5. Amphibians The amphibian skin has much in common with that of cyclostomes, being highly glandular, scaleless, and with a relatively thin corium (Fig. 146). The epidermis, although consisting of several layers, is nevertheless thinner than that of cyclostomes. The glands, however, are of a mor
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 210 Biology of the Vertebrates rant fishes, is an interwoven network of vertical and horizontal connective tissue fibers, practically undifferentiated into strata. 5. Amphibians The amphibian skin has much in common with that of cyclostomes, being highly glandular, scaleless, and with a relatively thin corium (Fig. 146). The epidermis, although consisting of several layers, is nevertheless thinner than that of cyclostomes. The glands, however, are of a more com- plicated type, being composed of several cells each, instead of a single cell as in cyclostomes. Although arising in the Malpighian layer of the epidermis, the compound integumental glands of amphibians do not remain in an epi- dermal position, as do the skin glands of cyclostomes, but push deeper down into the corium. Since amphibians are transitional animals, in and out of a water habitat, their plentiful glands help to keep the skin moist and suffi- ciently permeable for respiratory service. The vascularization of the amphib- ian skin is particularly pronounced during the critical period of metamor- phosis, when, in some cases, the unusual vertebrate condition of penetration of the epidermis by capillaries takes place. Epidermis !— Mucous Gland "Poison" Gland •Loose Connective Tissue of Derma ir~ Pigment Cell Subcutaneous Connective Tissue — Muscle Fig. 146. Section through the integument of a frog. (After Haller.) Among the higher amphibians which spend much of their time out of water, the corneum is differentiated in the epidermis with the result that ecdysis occurs, the dead outer layer sloughing off, sometimes in fragmentary rags and tatters. The corneum, however, is especially characteristic of land animals, not being as evident in aquatic forms. A secreted invertebrate-like cuticle, such as amphioxus and cyclostomes have, is transiently pres
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