Human anatomy, including structure and development and practical considerations . nail takesplace along the Hoor andbottom of the nail-groove,the last formed incrementof nail-substance pushingforward the previously dif-ferentiated material andthus forcing the nail to-wards the end of the relation of the epi-dermis of the nail-wall tothe substance of the plateis one of apposition only,production of the nail oc-curring in no part of thefold. Over the greaterextent of the latter all thetypical constituents of thecuticle are represented, butwithin the most proximalportion the stratum ger
Human anatomy, including structure and development and practical considerations . nail takesplace along the Hoor andbottom of the nail-groove,the last formed incrementof nail-substance pushingforward the previously dif-ferentiated material andthus forcing the nail to-wards the end of the relation of the epi-dermis of the nail-wall tothe substance of the plateis one of apposition only,production of the nail oc-curring in no part of thefold. Over the greaterextent of the latter all thetypical constituents of thecuticle are represented, butwithin the most proximalportion the stratum germi-nativum alone is present,the stratum corneum fad-ing away. Where thehorny layer exists, it restsdirectly upon the nail, butis diflferentiated from thelatter by being less denseand by its response to stains. As the nail leaves the groove, a part of the stratum germinativum of the nail-wall isprolonged distally for a variable distance over the dorsal surface of the nail-plate as a delicatemembranous sheet, the eponychium, which usually ends in a ragged abraded border. Corium. - 0»yj Transverse section of nail-wall and adjacent part of nail-plate and nail-bed. ^ 90. THE CUTANEOUS GLANDS. These structures include two chief varieties, the sebaceous and the sueatglands, together with certain modifications, as the ceruminous glands within theexternal auditory canal, the circumanal glands, the tarsal and ciliary glandswithin the eyelid and the mammary glands. In all the epithelial tissues—thesecreting elements and the lining of the ducts—are derivati\-es of the ectoblastand, therefore, genetically related to the epidermis. The Sebaceous Glaxds, Although these structures (glaodulae sebacae) are chiefly associated with thehair-follicles, in which relation they have been considered (page 1394), sebaceousglands also occur, if less frequently, independently and in those parts of the skin inwhich the hairs are wanting, as on the lips, angles of the mouth, prepuce and labiaminora. The
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