. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. iT->Granular Gland Cell — Beaker Gland Cell Malpighian Layer Fig. 144. Diagrammatic section through the integument of a lamprey eel, Petromyzon. (After Haller.) and characteristic glands of various kinds, principally mucous, that are dis- tributed among the cells of the thick many-layered epidermis. Epidermal cells in the skin of cyclostomes, from the deep-lying germinative Malpighian region to the surface, do not exhibit the same sort of progressive de
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. iT->Granular Gland Cell — Beaker Gland Cell Malpighian Layer Fig. 144. Diagrammatic section through the integument of a lamprey eel, Petromyzon. (After Haller.) and characteristic glands of various kinds, principally mucous, that are dis- tributed among the cells of the thick many-layered epidermis. Epidermal cells in the skin of cyclostomes, from the deep-lying germinative Malpighian region to the surface, do not exhibit the same sort of progressive degeneration toward a lifeless corneal condition that is character- istic of the mammalian skin. The outermost cells even retain their youthful cytoplasmic character and are active enough to secrete a thin cuticle over their exposed surfaces, a lingering trace perhaps of long-vanished in- vertebrate days. The horny teeth (Fig. 145), upon the surface of the pistonlike fleshy tongue and the wall of the buccal funnel, are the only epidermal cornifications in these animals. Periodically shed and renewed in the ortho- dox fashion of other corneal structures, they are thus to be regarded as corneal modifications of the epidermis. The corium, which is thinner than the epidermis in these primitive aber-. ^Buccal Funnel ^S^ Mouth „"Hr- Papillae fi-S-s* Teeth of Buccal Funnel sTeeth ofTongue —Eye Fig. 145. Ventral view of head of Petromyzon, showing oral sucker with horny "teeth" and piston-like "; (After Parker.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
