A Reference handbook of the medical sciences embracing the entire range of scientific and practical medicine and allied science . d point. Theaxis cylinder alone penetratesinto this core, having lost itsmedulla, and it ends in theupper portions either free oras a small button-like pro-tuberance. The Append.^.ges of thilSkin. The Nails,—Embryology.—The first steps in the dcvelopment of the nails occurin the third month of ftetallife, and consfst in the mark-ing out of the nail bed andfurrow. This is covered bythe ordinary stratum cor-neuni of that period of life,and it represents the epo-nyehiu
A Reference handbook of the medical sciences embracing the entire range of scientific and practical medicine and allied science . d point. Theaxis cylinder alone penetratesinto this core, having lost itsmedulla, and it ends in theupper portions either free oras a small button-like pro-tuberance. The Append.^.ges of thilSkin. The Nails,—Embryology.—The first steps in the dcvelopment of the nails occurin the third month of ftetallife, and consfst in the mark-ing out of the nail bed andfurrow. This is covered bythe ordinary stratum cor-neuni of that period of life,and it represents the epo-nyehium of Unna. Under-neath the eponychium theembryonic nail remains upto the fifth month. Accord-ing to KoUiker, theie ap-pears in the fourth month,between the eponychium andthe stratum mucosum, a la)-er of large, pale - colored,horny plates, which coverthe bed of the nail and re-present its primary form. The nail in its further growth increases in thickness(luite lapidly, possesses a free border by the sixth month,aud by the seventh month is fully formed. KoUiker alsoclaims that the development of the nail takes place from. Fig. .5213.—Hair from the Lipof a Human Embryo (After Rabl, from ) JY, Afferent nervefibre, which first gives off asmall forked branch in an up-ward direction, and then sub-divides into a ring-like phxiis(/Il iiimpletily surrouudiufthe outer sheath uf the hairroot which at this point issomewhat thickened. Thisplexus consists of a few nearlyhorizontiil fibrilirt tjetweenwhich run numerous verticalones; £)r, sebaceous gland. 562 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Skill and Its Ap-ptiidases. the entire uail bed, but Uona insists that he has ob-served tlie formatidii of a germinal spot in the matrix,from wliicli the emliryonic nail grows and pushes-itselfforward beneath the eiiouyehium. trenerid Cliiinicteristics.—The nails of hiuiian beingsare elastic structures of a horny texture situated upon
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