52 PHILOSOPHICAL TRANSACTIONS. [aNNO 1744. 



transudes through them in summer, their skins feel more coarse, hard, and rigid; 

 as they do in ardent fevers, with a dry skin. 5. Their exemption from some 

 cutaneous diseases, as the itch, prickly heat or essere, which no adult negroes are 

 troubled with, but those of fine and thin skins are most subject to, show the 

 thickness or callosity of their skins, which are not easily affected from slight 

 causes. 6. And not only the thickness, but also the opacity of their skins, will 

 appear, from their never looking red in blushing, or ardent fevers with internal in- 

 flammations, nor in the measles, nor small-pox ; where, though the blood must 

 be forcibly impelled into the subcutaneous vessels, yet it does not appear through 

 the epidermis. The like may be said of their veins ; which, though large and 

 shallow, yet do not appear blue, till the skin is cut. 7. In the jaundice, anasarca, 

 &c. the skin of negroes never shows the colour of the parts under it; though 

 visible enough in the eyes: of which Dr. M. saw a more convincing proof in some 

 negroes labouring under a bilious fever, in whom the serum of the blood, when 

 let, was of a deep bilious yellow, but no yellow colour appeared on the skin, 

 though plain enough to be seen in the eyes. 



Corollary. — Hence might be deduced one plain cause of the blackness of ne- 

 groes : for if the colour of the skin depends on what it transmits, and the skins of 

 negroes transmit no colour through them, they must needs appear black ; accord- 

 ing to the known doctrine of light and colours, that wherever there is a privation 

 of light or colour, there of course ensues darkness or blackness. But as most solid 

 bodies, which are not pellucid, do generally reflect some colour, which we know 

 no black body does, we shall next inquire into the particular make of their skins, 

 by which they are rendered incapable to reflect, as well as to transmit, the rays 

 of light. 



Prop. 3. — The Part of the Shin which appears black in Negroes, is the Corpus 

 Reticulare Cutis, and external Lamella of the Epidermis: and all other Parts are 

 of the same Colour in them with those of white People, except the Fibres iv hie h pass 

 between those Tivo Parts. — For a proof this proposition, we must examine the 

 structure of the skins of negroes more narrowly, which may be done after blister- 

 ing with cantharides, or after a scald or bum ; when their skins appear in the fol- 

 lowing manner: the cuticle, which is separated, appears nearly of the same colour 

 on the outside, as before such separation from the body ; but on the inner side is 

 almost as white as the same part in white people. This cuticle is almost always, 

 in blistering with cantharides, divided into two lamellae ; especially on the thighs, 

 where it is as thick almost as both the skin and scarf-skin of white people: the 

 surfaces, by which these two parts or lamellae of the epidermis cohere, are partly 

 white, and partly black ; for you may see many black fibres pervading the inner 

 lamella, and perforating the upper one, which appear like so many black spots on 

 these two surfaces, when separated from each other; but these black spots do not 



