XXtX.] 



THE SKIX. 



Mount in balsam. Or skin so hardened may be double stained in 

 bulk, first in borax-carmine and then in haemateiin. 



(b.} Haidi-n the skin in Miiller's fluid. 



(c.) For the layers of the epidermis fix say small pieces of the 

 skin in i per cent, osmic acid or Flemming's fluid, and harden in 

 alcohol. Stain sections in safranin. 



1. V.S. Skin, Palm of Hand. 



(a.) (L) The epidermis, consisting of many layers of stratified 

 squamous epithelium, resting on the cutis vera, dermis, corium, or 

 true skin. The latter consists of connective tissue, and is provided 

 with finger-shaped elevations or papillae, which project into the 

 deeper layers of the epidermis, the latter in the form of septa, dip- 

 ping in between the papillae (fig. 

 306). 



(/>.) The epidermis, composed 

 entirely of stratified epithelial cells. 

 Proceeding from the outside (fig. 

 307), observe 



(i.) The stratum corneum, of 

 variable thickness, consisting of 

 many layers of flattened or slightly 

 fusiform, clear, non-nucleated cells 

 united to each other. As the cells 

 are seen on edge, they are very thin. 

 Those on the surface are about to 

 be shed, and consist of keratin. 



(ii.) The stratum lucidum, a 

 thin, narrow, clear, homogeneous 

 layer, composed of two or more 

 layers of flattened cells, containing 

 sometimes a rod - shaped nucleus. 

 The cells do not stain well with 

 dyes. The eleidin granules seem to 

 become fused together and form the basis for cornification, as the 

 cells are changed and become corneous. 



(iii.) The stratum granulosum, a somewhat thicker layer, com- 

 posed of ovoid cells two or three rows deep. Each cell is distinctly 

 granular, and usually this layer stands out deeply stained, because 

 its granules of eleidin or keratohyalin are stained with the car- 

 mine. The cells, like the foregoing, are devoid of "prickles." 



(iv.) The stratum Malpighii, several layers of more plastic cells. 

 At the lowest part, where they rest on the papillae of the true skin, 

 the cells prickle-cells are smaller and columnar in shape (with 

 oval, vertically-placed nuclei), but above this they become more 

 spheroidal or polygonal, and each one is distinctly nucleated. 



FIG. 



. 306. V.S. Skin of Palmar Surface 

 of Finger. F. Fat ; P. T.S. Pacinian 

 corpuscle. 



