SCALP. NAIL. 85 



Scalp, V.S. Htiman. (p. 11, s. 22 & 24, c. P., m. B.) (L) The 

 hair follicles which are set aslant consist of a central hair (shaft 

 and bulb) closely invested by the inner and outer root sheaths 

 of epithelium, which are respectively continuous with the Horny 

 layer and Rete mucosum of the surface. Trace the connection. 

 Covering these is the thin Dermic coat, a surface condensation 

 of fibrous tissue. The sebaceous glands form compound saccu- 

 lated masses outside the follicles, into which their ducts open 

 not far from the surface. Further down find the Erector Pili, 

 a band of non-striped muscle which stretches across the obtuse 

 angle formed by the follicle with the surface of the skin. 

 Observe its method of attachment at both ends. (//) Examine 

 the constitution of the root sheaths, and trace them to the bulb 

 and over the vascular papilla situated within it. Make out 

 the formation of the hair at its bulb from the epithelial cells of 

 the sheaths. Examine the secreting cells of the glands ; the 

 lumen is filled with cells, which break up into granules of 

 sebaceous material. 



Scalp, human, horizontal S. (p. the same as the preceding.) 

 Examine the root sheaths of the hair follicles especially, and 

 the other features previously mentioned. 



Nail. Human foetal finger. V.L.S. (p. 15, s. 22 & 24, 

 c. P., m. B.) (L) On the dorsal aspect of the finger, and near 

 its tip, find the obliquely placed invagination of epidermis in 

 which the root of the nail is buried. At this early stage 

 the nail appears little more than a thickening of the horny 

 layer. A T.S. is required to show the mucosal ridges which 

 only become marked later. Note, besides, in other parts of the 

 skin, the developing sweat glands, which may only be present 

 as columnar in vagina tions of the rete mucosum. Examine 

 also the developing phalanges with their cartilaginous ends 

 and the marrow in their interior. 



