378 NUTRITION. 



the whole bulb looks nearly black. The sources of the 

 material out of which the cells form themselves are at least 

 two ; the inner surface of the sheath or capsule, which 

 dips into the skin, enveloping the hair, and the surface of 

 a vascular pulp which fits in a conical cavity in the bottom 

 of the hair-bulb. 



Such is the state of parts so long as the growing hair is 

 all dark. But as the hair approaches the end of its 

 existence, instead of the almost sudden enlargement at its 

 bulb, it only swells a little, and then tapers nearly to a 

 point ; the conical cavity in its base is contracted ; and the 

 cells produced on the inner surface of the capsule contain 

 no pigment. Still, for some time, it continues thus to live 

 and grow ; and the vigour of the pulp lasts rather longer 

 than that of the sheath or capsule, for it continues to pro- 

 duce pigment-matter for the medullary substance of the 

 hair after the cortical substance has become white. Thus 

 the column of dark medullary substance appears paler and 

 more slender, and perhaps interrupted, down to the point 

 of the conical pulp which, though smaller, is still distinct, 

 because of the pigment-cells covering its surface. 



At length the pulp can be no longer discerned, and un- 

 coloured cells are alone produced, and maintain the latest 

 growth of the hair. With these it appears to grow yet 

 some further distance ; for traces of the elongation of their 

 nuclei into fibres appear in lines running from the inner 

 surface of the capsule inwards and along the surface of the 

 hair ; and the column of dark medullary substance ceases 

 at some distance above the lower end of the contracted 

 hair-bulb. The end of all is the complete closure of the 

 conical cavity in which the hair-pulp was lodged, the 

 cessation of the production of new cells from the inner 

 surface of the capsule, and the detachment of the hair 

 which, as a dead part, is separated and falls'. 



Such is the life of a hair, and such its death ; which 

 death is spontaneous, independent of exercise, or of any 



