EPIDERMIS. 251 



By scraping the soles of the feet after immersion in warm 

 water ; the white and powdery material which is obtained, 

 often in large quantities, examined with the microscope, will 

 be found to consist of epidermic scales. 



By the use of the warm bath ; floating on the surface of 

 the water will be observed more or less of a thin and whitish 

 scum ; this consists of desquamated epidermis. 



By rubbing the moist skin with a rough towel ; a consi- 

 derable amount of epidermis visible to the naked eye will be 

 removed. 



The skin of new-born children is frequently observed to 

 be covered with a white and soap-like crust ; this, examined 

 with the microscope, will be found to consist of epidermic 

 scales mixed up with sebaceous matter. 



The last proof to be adduced of the desquamation of the 

 epidermis is one derived from disease ; after inflammation of 

 the skin, whether that of erysipelas, scarlatina or measles, 

 the epidermis peels off, a new one being previously formed 

 beneath the old. 



Amongst many of the amphibia and reptiles, the casting 

 of the epidermis is a periodical occurrence ; in man, on the 

 contrary, it is a constant and gradual process normally, 

 although it is also occasionally periodic from disease. 



USES OF THE EPIDERMIS. 



The principal uses of the epidermis are threefold. 



The first and chief use is to serve as a protection to the 

 more delicate parts which lie immediately beneath it. 



The second is to prevent the too rapid dissipation of the 

 caloric of the system. 



The third use has reference to secretion. It is evident, 

 however, that the importance of the epidermis as a secre- 

 ting organ is not considerable, seeing that the external 

 surfaces of the body do not require to be kept moist, to the 

 same extent as the internal. That the epidermis does not 



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