264 



THE TISSUES, 

 Fig. 168. 



Development of second eyelashes (infant, one year old). A. Formation of matrix of second hair. 

 B. Incipient development of the young hair. c. The same more advanced and pushing up the old 

 hair. D. The young hair emerging from the opening, and the old one about to fall out. a. External 

 root-sheath. &. Internal do. of young hair, c. Cavity for the formation of papilla, d. Bulb of old 

 hair. e. Its shaft. /. Bulb of young hair. g. Its shaft, h. Its point, i, i. Sebaceous glands. 

 Jc, k. Sweat ducts. 1. Passage of external root-sheath into the stratum Malpighii of the skin. m. 

 First appearance of young hair. 



sacs, and thus displacing the first hairs, after cutting off their supply 

 of nourishment. The striking analogy in these particulars of the 



hairs to the teeth, will become ap- 

 parent when we come to speak of 

 the development of the latter. 



Before the old hair falls out, it 

 becomes entirely horny in consist- 

 ence, and its bulb is no longer soft 

 and cellular, but solid and fibrous 

 like the shaft, with a clavate en- 

 largement. (Fig. 169.) 



This condition marks the end of 

 development and of growth; and 

 all hairs which fall out present it. 



Old hair falling out. A, shows a diminished activity 

 of growth by the small amount of pigment in the 

 cells of the pulp, and the interrupted line of dark 

 medullary substance. At B, provision is made for 

 the formation of a new hair, a new pulp appearing in 

 connection with the old one. At c, the hair has died 

 and fallen out, deprived of its sheath and of the cells 

 composing the pulp of a living hair. 



