Textbook of normal histology: including an account of the development of the tissues and of the organs . Within the subcutaneous layer, in many regions,numerous corpuscles of Vater are present. The hair-folliclesreceive a considerable part of the nerves of the corium, the medul-lated fibres forming loose net-works around the follicles, which theyaccompany as far as the sebaceous glands, where they divide into thenaked fibrillae which are traceable with certainty as far as the glassymembrane and probably end within the external root-sheath. THE DEVELOPMENT OF THE SKIN AND ITS APPENDAGES. The de
Textbook of normal histology: including an account of the development of the tissues and of the organs . Within the subcutaneous layer, in many regions,numerous corpuscles of Vater are present. The hair-folliclesreceive a considerable part of the nerves of the corium, the medul-lated fibres forming loose net-works around the follicles, which theyaccompany as far as the sebaceous glands, where they divide into thenaked fibrillae which are traceable with certainty as far as the glassymembrane and probably end within the external root-sheath. THE DEVELOPMENT OF THE SKIN AND ITS APPENDAGES. The development of the skin in-cludes the participation of the ecto-derm and the mesoderm, which con-tribute respectively the epidermis andthe corium. The history of the epi-dermis is closely identified with that ofthe ectoderm. In the earliest stage thelatter consists of a single layer oflow cuboidal cells ; later an addi-tional superficial stratum, the epi-trichium, becomes differentiated, thetwo layers of the ectoderm probablyalready indicating the corneous andMalpighian strata of the future epid Fig. Section of developing skin fromhuman foetus of three and a halfmonths : a, layer of cuboidal cells rep-resenting stratum Malpighii; b, polyhe-dral elements forming superficial layers;c, outermost flattened plates, probablythe remains of the epitrichial layer ; d,mesodermic tissue forming corium. ermis, although the precise 278 NORMAL HISTOLOGY. relation between the horny layer and the embryonal cells is still un-settled. It is probable that where a well-developed stratum corneumexists the parts of this external to the stratum lucidum represent themetamorphosed epitrichium ; where, however, a true cornified layeris wanting and the superficial cells belong to a highly-developedstratum lucidum, as in the nails, the epitrichium is not represented,since in this case the entire epidermis is derived from the deeperlayer of ectodermic tissue (Bowen, Minot). With the generalgrowth the layers
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Keywords: ., bookauthorpiersolgeorgeageorgea, bookcentury1800, bookdecade1890
