22 THE HUMAN BODY. 



It is a black or brownish substance, more or less abundant 

 according to the region of the body, individual, or race, but 

 constantly existing in normal conditions, alike in Europeans 

 and in the people of Soudan and Australia. The presence 

 of this pigment and its unequal distribution contribute to 

 the variety of complexion exhibited in the white race. 



Under the pigmentary layer is the dermis, the thickest and 

 most resistant part of the skin ; it is white, semi-transparent, 

 and is composed of fibres of cellular tissue, fasciculated and 

 very dense; of elastic fibres, ramified and disposed in net- 

 work ; and of contractile fibre cells. 



Immediately under the epidermis the surface of the dermis 

 is covered with papilla, little conical or rounded elevations 

 formed by the extremities of the nerves and vessels, which 

 are divided into nervous papillae and vascular papillae. Each 

 nervous papilla is surmounted by an organ, which from its 

 function and its microscopic dimensions is called a tactile 

 corpuscle or corpuscle of touch. They are much less numerous 

 than the other papillae, and are not found everywhere on the 

 skin. They are seen on the palm of the hand and on the 

 lateral and palmar surfaces of the fingers, on the sole of the 

 foot, on the tongue, the lips, and some other points. The 

 epidermis follows exactly the shape of these papillae, and 

 thus forms, in tracing the furrows which separate them, those 

 graceful meandering lines and elegant curves which we see 

 especially on the palm of the hand. Very dense at its thickest 

 portion, the structure of the dermis grows more relaxed on 

 approaching its lower face, and forms spaces or areolae in 

 which adipose tissue is developed, and at last it intimately 

 unites itself to the subcutaneous cellular tissue, from which 

 the dermis receives, and to which it sends, fibrous prolonga- 

 tions. 



Gratiolet is inclined to admit that these so-called nervous 

 papillae are almost entirely wanting in nerves. He compares 

 them to little keys, so to speak, pressing lightly on a very 

 sensitive surface; and leaving there only very limited impres- 

 sions. 



Other connections also exist between the tegument and 

 the subcutaneous cellular tissue: these are the nerves and 



