OF THE NAILS. 



159 



With regard to the structure of the proper substance of the 

 nail, it can hardly be made out without the action of reagents. 

 In perpendicular sections we see, particularly in the body, noth- 

 ing but horizontal, fine, straight, or curved, closely approximated 

 lines, which one would be inclined to consider as the optical 

 expression of delicate, super-imposed lamellae, and between these, 

 a multitude of elongated, horizontal, opaque or peculiar reddish- 

 transparent strise, evidently nuclei. Only upon the most posterior 

 part of the root, and on the under surface, where it meets the 

 stratum Malpighii, do more or less distinctly flattened cells with 

 nuclei appear disposed in layers. Horizontal sections show even 

 less than the perpendicular ones ; exhibiting a pale transparent 

 substance, granular here and there, and mostly without indi- 

 cation of any structure whatsoever, occasionally with very indis- 

 tinct contours of plates similar to those of the horny layer of 

 the epidermis. Very different are the appearances presented 

 after treating the nail with alkalies and certain acids. 



If the substance of the nail 

 be boiled in dilute caustic 

 soda, it becomes changed 

 upon the first bubbling of 

 the fluid into a beautiful cel- 

 lular tissue (fig. 62, A, B), 

 whose polygonal elements 

 all, without exception, the 

 deep as well as the su- 

 perficial, possess nuclei of 

 0-0030— 00046"' in length 

 and breadth, and 0'002"' in 

 thickness, which, according 

 as they turn their surfaces 

 or their edges to the observer, appear as rounded, very 

 pale, and finely-granulated discs, or as long, narrow, dark 

 contoured rods ; it deserves further to be noted, that together 

 with these, large and very pale nuclei of 0"006 — 001"' and 

 more, occur in considerable numbers, probably owing their 



Fig. 62. 



existence to the excessive action of the 



reagent 



which has 



Fig. 62. 



Nail plates boiled with caustic soda, x 350. A, from the side ; B, from 

 the surface : a, membranes of tbe distended elements of the nail ; b, their nuclei, 

 from the surface ; c, from the side. 



