THE SKIN. 561 



their ultimate termination is not known. Sometimes the tactile 

 corpuscle exhibits deep furrows, indicating that it is composed of 

 several tactile buds (Merkel), or two or more isolated tactile cor- 

 puscles are attached to one or two nerves (Oehl, Thin, and 

 others). A. R. Robinson * maintains that the nerve does not ter- 

 minate in the tactile corpuscle, but passes on into the rete 

 mucosum ; the axis-cylinder generally changes the direction of 

 its course after leaving the corpuscle, and terminates between 

 the epithelia. 



Non-medullated nerve fibers are known to terminate in the 

 walls of the capillary blood-vessels of the papillary layer 

 (Tomsa), and in the rete mucosum (Langerhans, Flemming). 

 In the latter situation a delicate beaded reticulum of nerve 

 fibrillae can be brought to view, especially by staining with 

 chloride of gold, but the question is unsettled whether or not the 

 nerves enter the epithelia. Tomsa noticed a delicate reticulum of 

 nerves around the coils of the sweat-glands ; others have described 

 such a reticulum in the follicle and the papillae of the hair. 



(6) The Epithelial Cover of the Integument. The outer layers 

 of the stratified cutaneous epithelium are squamous, the middle, 

 which are the most abundant, cubodial, and the boundary, toward 

 the papillae, consists of a single row of columnar epithelia. The 

 columnar and cuboidal epithelia are endowed with vital proper- 

 ties, of which the flat epithelia are deprived by their transforma- 

 tion into a horny material. The living portion of the epithelium 

 bears the name of rele mucosum, or rete Malpighii-, the horny 

 portion is the epidermis proper. Between these two layers 

 appears a narrow zone of nearly compact glistening epithelia, 

 running parallel with the surface j Oehl has designated this layer 

 the stratum lucidum. It is sometimes well marked, especially 

 in vertical sections of the skin covering the palms of the 

 hands and soles of the feet ; sometimes it is not discernible. At 

 other times alternating layers are found, consisting of granular, 

 nucleated, and of nearly homogeneous epithelia, destitute of 

 nuclei j but as these formations are not constantly present, we 

 are not justified in dividing, as some authors have done, the 

 epithelial cover of the integument into four or five distinct 

 layers. 



The epithelia nearest the papillary layer are often indis- 

 tinctly columnar, and of a diffuse brownish color, holding more 



* "A Manual of Histology," by Thomas E. Satterthwaite. New-York, 

 1881. 



36 



