THE SKIN AND THE SENSE-ORGANS. 



Fig. 228. 



SSSrss?' A 



I. THE SKIN AND ITS APPENDAGES. 



THE general characters and the colouring- of the skin have already 

 been described (pp. 4 to /). The skin consists of the cuti* rera or 

 corium, and the cuticle or epidermis, and 

 is possessed of numerous glands. 



a. The epidermis (Figs. 228, 230) con- 

 sists of several layers of epithelial cells, 

 those of the deepest layer being more or 

 le-s columnar in form, those of the middle 

 layer shorter and polygonal, while those of 

 the superficial layer are flattened, very 

 transparent. and horny. 



All the surfaces of these cells are serrated, 

 the serrations being, however, with diffi- 

 cultv seen on the free surface of the super- 

 ficial cells (Ley dig). Each cell has a 

 distinct nucleus ; in the deeper cells the 

 nucleus is oval, broad, and rounded, in the superficial cells flattened 

 and thin. 



The surface of the epidermis (Fig. 230) forms a very beautiful 

 mosaic of flat cells, chiefly hexagonal in form, with pale, cen- 

 tral, oval nuclei. Here and there two adjacent cells appear to 

 enclose a semilunar space (Fig. 228 I)}; these spaces are occupied 

 by peculiar cells (goblet-cells, E. Schultze ; mucous cells, Leydig), 

 which do not belong to the superficial cells but the layer of cells 

 immediately beneath the horny layer (Schultze, Pfitzner). The 

 cells are rounded or flask-shaped, and closely resemble the epithelial 

 goblet -cells or chalice-cells. According to Rndneff they open on 

 the free surface by stomata ; this is, however, denied by Schultze 

 and <>tli 



C 



: -.'. .'.. 



Vertical section through the epi- 

 dermis from the head of Sana 

 rsculrnta ; after F. E. Schultze. 

 Magnified 600 times. 



.1 Horny layer. 



B Middle layer. 



C Deep layer. 



D Isolated mucous-cells. 



