Page:The American Cyclopædia (1879) Volume V.djvu/195

 COMPLEXION 191 frequently irregular, he continued in robust health. A curious case of change of complex- ion is narrated by Dr. Hutchinson of Kentucky, in the " American Journal of Medical Sciences " for January, 1852. The subject of this notice was a slave aged 45. He was born of black parents, and was himself perfectly black until the age of 12. At that time a portion of the skin an inch wide, encircling the cranium just within the edge of the hair, gradually changed to white, also the hair occupying that locality. A white spot next appeared near the inner canthus of the left eye, and from this the white color gradually extended over the face, trunk, and extremities, until it covered the entire sur- face. The complete change from black to white occupied about ten years, and but for his hair, which was crisped or woolly, no one at this time would have supposed that his pro- genitors had any of the characteristics of the negro, his skin presenting the healthy vascular appearance of a fair-complexioned European. When about 22, dark-colored or brown spots began to appear on the face and hands, being limited to those portions of the surface exposed to light. Thus it appears that the coloring matter that gives rise to the various hues in the complexion is sometimes produced in the skin of persons born white, and at others removed from those born black. Now it is hardly possible, in view of these facts, to sup- pose with Flourens that the discoloration which takes place in the skin of the white person is totally different in kind and has its seat in a different structure from that which produces the black or tawny hue in the colored races. Microscopical investigations have done much to solve the doubt that hangs over this ques- tion. Henle, in examining the skin of the ne- gro by the aid of the microscope, discovered, besides the order of cells usually found, others containing the black pigment which imparts the color to the African's skin. He found these last aggregated especially on those parts of the rete mucosum which project and correspond with the furrows of the surface of the cutis. Dr. Simon of Berlin took pains to ascertain whether the discolorations which occasionally take place in the skin of persons of European extraction depend upon the presence of similar cells filled with pigment ; and in examining the discolored portions of such skins, as the areola around the nipple, he found that the discolora- tions depended on the presence of cells filled with pigment in the rete mucosum. The shape and size of these cells correspond with those described by Henle as existing in this portion of the skin of the African, and which imparts to it its peculiar color. Simon also examined many of those abnormal discolorations that take pla,ceiRn(Evimaterni, or congenital spots, moles, and summer freckles, and found in each that the coloring substance was contained in the rete. All of these discolorations are related there- fore, Simon concludes, to the normal and natural colorations in the skin of the negro. The rete 218 VOL. v. 13 mucosum, which derives so much importance from its being the seat of the coloring matter that gives rise to the varieties of complexion observable among the different races of man- kind, is found by later microscopical researches, and especially those of Kolliker, not to be a distinct structure, but to consist of the more recently formed parts of the epidermis, whose cells are not yet consolidated by the formation of horny matter in their interior. The pig- ment cells which secrete coloring matter, as first shown by Simon, are not readily distin- guishable in the epidermis of the white races, except in certain parts of the body, as around the nipple, but are quite perceptible in the new layers of the epidermis of the negro. It was supposed by Simon that these cells gradu- ally become flattened, and passing to the sur- face give the dark tint observable in the col- ored races. The examinations of Kolliker es- tablish the fact that the cells containing col- oring material do not change their place, but remain stationary in that portion of the epi- dermis in which they were first developed. Dr. Carpenter says : " The epidermis or cuticle covers the exterior surfaces of the body as a thin, semi-transparent pellicle, which is shown by microscopical examination to consist of a series of layers of cells, which are continually wearing off at the external surface and are be- ing renewed at the surface of the true skin, so that the newest and deepest layers gradually become the oldest and most superficial, and are at last thrown off by desquamation. In their progress from the internal to the external sur- face of the epidermis, the cells undergo a se- ries of well marked changes. When we exam- ine the innermost layer we find it soft and granular, consisting of nuclei in various stages of development into cells, held together by a tenacious semi-fluid substance. This was for- merly considered as a distinct tissue, and was supposed to be the peculiar seat of the color of the skin ; it received the designation of rete mucosum. Passing outward, we find the cells more completely formed ; at first nearly spheri- cal in shape, but becoming polygonal where they are flattened one against another. Min- gled with the epidermic cells we find others which secrete coloring matter instead of horn ; these are termed pigment cells. The most remarkable development of pigment cells in the higher animals is on the inner surface of the choroid coat of the eye, where they have a regular arrangement, and form several lay- ers known as pigmentum nigrum. The black color is given by the accumulation within the cells of a number of flat, oval, or rounded granules of extreme minuteness, which exhib- it an active movement when set free from the cell, and even while enclosed within it." Quain and Sharpey say: "Many of the cells of the cuticle contain pigment, and often give the membrane more or less of a tawny color, even in the white races of mankind. The blackness of the skin of the negro depends