PART THIRD 

 ORGANS 



THE SKIN 



The skin consists of (1) the epidermis (or scarf skin), which 

 everywhere covers and protects (2) the derma (corium or true 

 skin ) . 



The epidermis varies greatly in thickness in different locations; 

 and in the thicker portions several layers may be differentiated. 

 It is composed entirely of cells, while the derma is fibrous. 



1. Stratum Corneum, ) T 



2. Stratum Lucidum, j Horn y Lft y er - i & 





r^ li \ 3. Stratum Granulosum, 1 AT , . , . T 



'M 4. Stratum of Prickle Cells, Malpighian Layer or 



t 1 5. Stratum of Columnar Cells. } Eete Mucosnm. J f 



The stratum corneum consists of old, exhausted, flattened, and 

 desiccated cells, which are constantly falling from the entire sur- 

 face of the body. Dandruff consists of impacted cells from this 

 source. Those portions most frequently exposed to friction e.g., 

 the palms of the hands and the soles of the feet are protected ~by 

 a corneous epidermal layer of great thickness. 



The stratum lucidum, or clear layer, presents cells in form not 

 unlike those in the preceding stratum ; they are, however, trans- 

 lucent. This is properly a part of the previous stratum, is often 

 absent, and frequently very difficult of demonstration. The 

 stratum lucidum and stratum corneum owe their characteristic 

 properties largely to the development in their cells of a substance 

 called keratin. 



The stratum granulosum, or granular layer, is composed of 

 flattened cells containing opaque granules of eleidin, which is 

 related to the keratin of the horny layers. 



Immediately beneath the last-named layer, the cells become 

 strikingly altered in form and appearance. The pricUle cells are 



(92) 



