CHAP. XIV.] NAILS AND HAIRS. 417 



of the finger, and only to become free by a rupture of this con- 

 nexion after birth. Thus the nail covers that portion of cutis 

 which is without cuticle. It has been frequently discussed whether 

 the cuticle is continued over and under the nail ; but this is a ques- 

 tion of words only, the nail being the same essential structure as the 

 cuticle. The border of the root of the nail is jagged, thin, and soft, 

 and consists of newly formed substance : the deep surface of the 

 body^is also soft, and marked by longitudinal grooves, correspond- 

 ing to the papillary ridges on the surface of the matrix. These soft 

 under-parts consist of nucleated particles, similar to those of the 

 deep layers of the epidermis. The more superficial laminse of the 

 nail are more and more dense and fibrous ; but, when treated with 

 acetic acid, some imperfect traces of nuclei may still be detected in 

 them. The nail grows both at the root and on the deep surface of 

 the body ; as the substance furnished by the root advances towards 

 the free edge, it receives accessions from the surface of the matrix. 



Hairs are found on all parts of the surface, except the palms of 

 the hands and the soles of the feet, and differ much in length, thick- 

 ness, shape, and colour, according to situation, age, sex, family, or 

 race. We may select one of average size for a description of their 

 structure and mode of growth. The shaft of the hair is that part 

 which is fully formed, and which projects beyond the surface. Tracing 

 this into the skin, we find it lodged in a follicular involution of the 

 basement membrane (fig. 87, a), which usually passes through the cutis 

 into the subcutaneous areolar tissue. This hair-follicle is bulbous at 

 its deepest part, like the hair which it contains. Its sides have a 

 cuticular lining, 6, continuous with the epidermis, and resembling 

 the cuticle in the rounded form of its deep cells and the scaly cha- 

 racter of the more superficial ones, which are here in contact with 

 the outside of the hair, c. The hair grows from the bottom of the 

 follicle, and the cells of the deepest stratum there resting on the 

 basement membrane are very similar to those which in other parts 

 are transformed into scales of cuticle. A gradual enlargement occurs 

 in these cells as they mount in the soft bulb of the hair, which indeed 

 owes its size to this circumstance. If the hair is to be coloured, the 

 pigment grains are also here developed for the most part in scat- 

 tered cells, which may send out radiating processes at other times, 

 in a diffused manner around the nuclei of the cells generally. It 

 frequently happens that the cells in the axis of the bulb become 

 loaded with pigment at one period, and not at another ; so that, as 

 tlicy pass upwards in the shaft, a dark central tract is produced of 

 greater or less length, often only in irregular patches, and the hair 



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