26 INTRODUCTION. 



Microscopical investigation has shown that the skin does net consist 

 of continuous membranes, hut is composed of several layers jf cells 

 not separated from each other by such definite lines. Ilcnle hr.s found 

 that the apparently membranous parts, which give color to various 

 surfaces, are also of a cellular structure, and not properly mem- 

 branous; in the skin of the Negro he found numerous irregularly 

 spherical cells containing the black pigment to which the color is 

 due ; they were most numerous on those parts of the rete which pro- 

 ject and correspond to the furrows of the cutis. Dr. Simon, of 

 Berlin, has found that the various discolorations of the white skin 

 depend on the presence of similar cells filled with pigment, and that 

 they are related on the one hand to the normal coloration of the 

 Negro skin, and on the other to the disease termed melanosis, in 

 which " the production of pigment cells keeps pace with a change' 

 from the normal or healthy state of organization in the affected parts." 



He thence concludes that there is no organic difference between 

 the skin of the Negro and the European, which marks them as dis- 

 tinct species. It may also be added that the epidermic tissue, to 

 which the horny tissue of many animals corresponds, and which is the 

 seat of the variations in color and in the hair of man, " is precisely 

 that part of the organic system which undergoes the most striking and 

 even surprising alterations." The complexions of mankind are not 

 permanent characters ; there are many changes from white to black, 

 and vice versa, and both complexions are seen in the undoubted prog- 

 eny of the same stock ; so that no argument, according to Prich- 

 ard, can be drawn from color against the original unity of the human 

 species. 



The human races have also been distinguished by the color, quality, 

 and quantity of the hear ; these national diversities probably do not 

 exceed the measure of variety occurring in different families of the 

 same nation. Some Europeans are said to have hair quite as crisp 

 and curly as that of a Negro ; even among Negroes, we find every 

 rariety from a so-called " woolly" hair to curled or even flowing 

 hair; the same is affirmed of the natives of the Southern Ocean, 

 where there is no intermixture of races. The nature of the Ne^ro 

 hair has been the subject of much discussion, as it was supposed to 

 possess characters indicating a distinct species. The Negro hair is 

 called " wool," meaning that it approaches the wool of animals. 

 The fibre of true wool is rough on its surface, and has a feathered 

 or barbed edge ; this is at the same time the cause of its felting prop- 

 erty, and the mark which distinguishes it from hair. Examined 

 microscopically, the fibre of wool generally has serrated edges, 

 resulting " from a structure resembling a series of inverted cones, 



