HYPERTROPHY OF THE SKI*. 



soft cutaneous warts or moles. But, even here, the hypertrophy does 

 not involve all the tissues of the skin hi equal degree. In the majority 

 of the projecting " mother's marks " and moles, there is a predominant 

 development of pigment and hair ; their brown or blackish color and 

 the strong growth of hair with which they are covered being one of 

 their striking features. 



Large accumulations of horny epidermic cells are often found upon 

 certain spots of the body ; the callosities, the corns (clavi), and the 

 cutaneous horns, originate in this way. Callosities consist of low 

 flat, horny elevations, of a rounded or irregular form ; the condition of 

 the cutis which they cover being either normal or slightly hyperaemic. 

 Callosities are most apt to form at points exposed to irregular pres- 

 sure. Hence they are found upon the heels and upon the soles of the 

 feet of most persons ; upon the hands of blacksmiths, locksmiths, and 

 other mechanics ; and upon the index-fingers of tailors and of seam- 

 stresses. Corns are small, but very hard and thick conical callosities, 

 induced by the pressure of the boots or shoes, and which cause a cir- 

 cumscribed atrophy of the skin. The so-called cutaneous horns con- 

 sist in an excessive hypertrophy of the epidermis over a circumscribed 

 spot of skin. Some horns do not spring from the papillae of the skin, 

 but develop from dilated hair-follicles, and may be regarded as mon- 

 strous hairs. There is also a diffuse hypertrophy of the epidermis, 

 which is accompanied by hypertrophic development of the papillas of 

 the skin. Of this affection, which, when of moderate intensity, is 

 called pityriasis, and when more severe is called ichthyosis^ we shall 

 treat more in detail hereafter. 



The brunette complexion, congenital in some persons, is due to a 

 copious deposit of pigment in the cells of the rete Malpighii. Another 

 congenital anomaly, which is seen in many persons, consists in a heavy 

 deposit of pigment in circumscribed patches upon the rete Malpighii, 

 producing brown or black spots (chloasmata, melasmata). When the 

 patches are of wider circumference, they are called pigmentary naevi 

 (ncevus spilus). If only as large as a lentil, they are called ephelides 

 or lentigines (Leber-flecke). The pigmentary marks and spots, which 

 are unaccompanied by hypertrophy of the cutis, and which, therefore, 

 do not project above the surface of the skin, are likewise often covered 

 with hair. In the majority of persons the formation of pigment in the 

 rete Malpighii is increased under the influence of the sun's light and 

 heat, and under that of wind and dampness ; hence, among soldiers, 

 field-laborers, and particularly among seafaring persons, the exposed 

 portions of the skin assume a uniform brown color. *It is remarkable, 

 too, that in some persons irritation of this kind does not produce such 

 deposit of pigment, or, as people say, they do not become " sunburnt " 



