On the Sense of Feeling: 293 



The cause of the dark tinge has been popularly ascribed to the heat of the 

 sun .; if so, a vast number of years must be required to produce the effect, 

 for there is certainly but little analogy between the colour of the negro, 

 and the ordinary tan of an European who has been exposed to the sun. 

 Besides which, such a tan is never communicated to his offspring. More- 

 over, the blackest skins are not those exactly within the torrid zone, and 

 there are nations near the equator, whose hue is almost as light as our own. 

 Tliere are certain shades, produced by artificial means, which are not 

 re-absorbed : they seem to occupy the seat of the pigment. Such is the 

 tinge produced by the internal use of nitrate of silver. This tinge never 

 affects a cicatrix, that is, a place where the dermis and epidermis are ad- 

 herent, and the intermediate structures wanting. 



We have enumerated, then, as existing in the substance of the dermis, 

 four sets of structures : 1. The nervous filaments , terminating in the pa- 

 pillae of the dermis, the proper organs of tact. 2. The exhalant glands, 

 and their long spiral ducts, pouring out the perspiration in successive 

 drops upon the surface. 3. The inhalant glands or absorbent vessels, 

 rising by a multiplicity of tendrils just below the actual surface of the 

 body, and uniting to form a larger trunk, probably in its turn also tributary 

 to the neighbouring vein. 4. The glands for the secretion, and ducts for 

 the deposition, of the colouring matter, or pigment, upon the surface of the 

 dermis. 



Besides these, are two other sets of organs whicli we shall describe 

 presently. 



We next arrive at the second and superficial division of the integuments, 

 the epidermis. 



The epidermis, cuticle, or scarf-skin, as it is indiscriminately called, is 

 a transparent, inorganised pellicle, thrown like a delicate veil over the 

 whole surface of the body, dipping into the various cavities, and shielding 

 them from the rude contact of external impressions. Thus we find it 

 spread over the eye as tlie conjunctiva, upon the cavities of the nostrils as 

 the pituitary membrane ; and shutting out all access to the internal ear, 

 by spreading itself over the membrane of the tympanum. Its office is to 

 protect the acutely sensible papilla; of the cutis from too severe an im- 

 pression, leaving their sensibility in sufficient perfection to answer the ordi- 

 nary purposes of life. 



Agreeably to this intention, it is found to be thicker in those parts whicli 

 arc most exposed, as the soles of the feet, and palms of the hands : and 

 that this is a prospective provision, is shewn from the thickening being 

 found in the new-born infant ; though, at the same time, tliis defence is 

 often produced to meet an emergency ; and it is remarkable that labour and 

 continued pressure, instead of permanently abrading and making the skin 

 tender, cause it to assume a tiiick and horny structure, effectually preserving 



No. ;"..— Vol. I. 2 Q 



