162 



SPECIAL HISTOLOGY. 



Fig. 61. 



...A: 



of the root, and forms by itself the above-mentioned laminae on the under 

 surface of the nail. Its thickness at the posterior part of the root upon 



the under side measures 0-12, on 

 the upper, 0-14 of a line ; close be- 

 hind the margin of the root, direct- 

 ly from behind forwards, 0-24- 

 0-26 of a line ; on the body of the 

 nail on the laminae, more poste- 

 riorly and at the edge 0-04-0-05 

 of a line; in the middle, 0-06 even 

 0-08-0-96 and 0-12; between 

 these, 0-032-0-04 of a line. 



The Malpighian layer of the 

 nail, like that of the epidermis, 

 consists wholly of nucleated cells, 

 and agrees in all essential points 

 with it, except that the deep por- 

 tion contains many layers of elon- 

 gated (of 0-004-0-007 of a line) 

 perpendicular cells, in conse- 

 quence of which a striated appearance is produced, which has misled 

 Gunther, and probably Rainey also,* into supposing the existence of 

 peculiar glands under the nail. In the Negro, according to Be'clard 

 (Anat. Gendrale, p. 309), the stratum Malpighii of the nail is black ; 

 and according to Krause (1. c. p. 124), its cells would in this case appear 

 to contain dark-brown nuclei, as well as yellowish-brown ones, in dark 

 Europeans. According to Hassall (p. 252), the younger cells of the 

 nail (i. e., those of the stratum mucosum\ generally contain pigment, 

 which I can confirm, at least in some cases. 



The horny layer of the nails, or its proper substance (Figs. 58 /; 60 

 &, /, m; 61 c), is that hard brittle portion which forms its upper part 

 and its free edge. The under surface of this layer is quite smooth, pos- 

 teriorly at the root ; further forward it exhibits sharp ridges separated 

 by broad furrows, which are inserted into the furrows of the mucous 

 layer of the nail. These ridges of the proper nail substance appear in 



FIG. 61. Transverse section through the body of the nail; magnified 250 diameters. 

 Jl, cutis of the bed of the nail ; .B, mucous layer of the nail ; C, horny layer of it, or proper 

 nail substance ; a, layers of the bed of the nail ; 6, layers of the stratum Malpighii of the 

 nail ; c, ridges of the proper substance of the nail ; rf, deepest perpendicular cells of the 

 mucous layer of the nail; e, upper flat cells of it; /, nuclei of the proper substance of the 

 nail. 



* [With respect to Rainey's observations, Reichert, in his Report for 1849-50 (" Mall. Arch.," 

 1850-51) says, that the observation as to the follicles is quite correct, and that with Dr. 

 Ammons, who had studied the growth and regeneration of the nails for some years, he had 

 seen such capsules containing horny cells, with especial distinctness upon the bed, of the 

 nail of the great toe. TRS.] 



