252 ELEMENTARY BIOLOGY. [XIIT. 



2. Take a piece of skin that has lain for a day or two in 

 solution of ammonia bichromate and then in alcohol : 

 imbed it, and cut sections perpendicular to its sur- 

 faces : mount in glycerine. Examine with a low 

 power; note 



a. The two layers of the skin, dermis and epidermis, 

 the former being much the thicker : note in the 

 dermis its deeper connective-tissue layer, and its 

 more superficial glandular layer immediately 

 beneath the epidermis. 



b. Examine with a higher power. 



a. The epidermis is seen to be made up of nume- 

 rous closely packed cells, arranged in several 

 layers. 



@. The deepest epidermic cells are granular, nu- 

 cleated, and somewhat oval, with their long 

 axes at right angles to the surface. 



7. Then come several rows of cells, also granular 

 and nucleated, but becoming smaller and 

 rounder as they become more superficial. 



8. The most superficial three or four layers of 

 cells are flattened parallel to the surface, are 

 not granular, and possess no apparent nucleus. 



e. Here and there a pigment-cell is seen among 

 the epidermic cells, and some of the latter con- 

 tains a few pigment-granules. 



f. The dermis, consisting fundamentally of white 

 fibrous and elastic tissues: its glandular and 

 non-glandular layers. 



