262 THE SOLIDS. 



that the subjacent dermis be not too deeply injured ; the 

 cicatrices remain for a considerable time nevertheless without 

 colour. 



The skin of the children of negro women does not acquire 

 its full depth of colouring for some days after birth. 



Pigment cells are developed at a very early period of intra- 

 uterine life. The uses of pigment in the skin are not well 

 understood ; that in the eye is doubtless of importance in the 

 discharge of the functions of that organ : it is known that 

 the Albinoes, in whom it is either absent or exists but in small 

 quantities, are incapable of supporting a strong light. 



Pigment cells of particular forms occur amongst some of 

 the lower animals. Those of the internal surface of the 

 choroid of fishes and birds, situated in front of the ordinary 

 coloured cells, have the form either of short sticks or clubs. 

 The argentine pigment of the iris and peritoneum of fishes is 

 composed of elongated corpuscles. The pigment cells placed 

 beneath the epidermis of the frog are for the most part 

 stellate. 



