418 CHANGE OF COLOR. 



and the remainder of it much lighter than it was originally. 

 At this time, some part of her face has an unnatural whiteness ; 

 but the skin of her forearms appears like that of a European in 

 a perfectly healthy state. This change of color is attended 

 with no unusual sensation ; so that if she did not see the altera- 

 tion, she would not suspect that her skin was any way different 

 now from what it had originally been. She does not appear 

 sensible that the white parts are more susceptible of irritation 

 from the rays of tbe sun than they were originally ; but they 

 are so mnch covered by her dress that the experiment has not 

 yet been fairly made. 



The first appearance of a change is slight diminution of the 

 dark color ; this change goes on gradually, and then small 

 spots appear, which are perfectly white. They gradually 

 increase, and run into each other, and thus a large white spot 

 is formed. 



In a former case, where this process had gone on to a great 

 extent, it is said that the black pigment was again deposited, 

 and the skin resumed its original blackness. 



These circumstances in negroes have been considered as 

 great deviations from the ordinary course of nature, but a 

 process very analogous to it sometimes goes on in persons who 

 are white. Thus, there are some in whom the skin becomes 

 much browner than natural in some parts of the body, parti- 

 cularly on the arms ; and in these brown portions, spots are 

 formed which are much more white than the natural color of 

 the skin. 



In such cases there appears to be a deposition of coloring 

 matter in the rete mucosum of the brown places ; while the 

 white spots are rendered more white than natural, either by an 

 absorption of the rete mucosum, or by a deposition of whiter 

 matter in it. 



The color of the rete mucosum sometimes undergoes a 

 temporary change in particular places. Thus, at a certain 

 period of pregnancy, a dark circle forms round the nipple. 



In some cases, where the peculiar whiteness occurs, the skin 

 becomes very susceptible of irritation from the rays of the sun ; 



