PERIDERM 



STRATUM GERMINATIVUM 



"^-SINGLE LAYER OF 



EPIDERMAL CELLS 



* DERMIS- 



DERMATOME 

 SOMITE 

 MYOTOME 

 SCLEROTOME 



STRATUM CORNEUM- 



_PERIDERM 



-STRATUM INTERMEDIUM 







.-i32~GE RMINATI VE STRATUM 

 DERMIS 



CONNECTIVE- T ISSUE 

 FIBERS 



• PERIDERM (EPITRICHIUM)— 



EPIDERMIS 



DERMIS 



^^', ,-^. 



SE BACEOUS-GLAND --<5' 't'^^ A' i '. ,^>^^, V' W/ 



RUDIMENT — ^ / 'h f '/ |'^^.-)^?CJ-,!. Ifj. 



lESENCHYMAL ,' \P - i ■ ' '/'/^l J:^^^ ft '■{ 



AGGREGATION ' ( \\ ^A ' ' W ^^f^'rU 



PERIDERM 





EPITHELIAL BED '^/\f-^'\'( '1^/ A ^f'O ^ .7i\ 



-EPIDERMIS j:WWM^M)\S 



OUTER SHEATH ts,\'„ I M ¥' I^^f'^W //) ' 



HAIR SHAFT >\ '!^ .Mf ^'S^W/^' 



HAIR CONE i*.- „ ' fMA i^^/j '< ' ■^' ff, 



HAIR CONE 

 INNER HAIR SHEAT 





HAIR BULB 

 PAPILLA 



MESENCHYMAL 



AGGREGATION 



BLOOD VESSELS 





^V G 



Fig. 272. Diagrams of developing hair. (A from Johnson: Carnegie Inst., Washington, 

 Publ. No. 226, Contrib. to Embryol., 6; C and D from Pinkus, Chap. 10, The develop- 

 ment of the integument, Keibel and Mall, 1910, Vol. I, Lippincott, Phila.) (A) Section 

 through epidermis of 24-somite human embryo. (B) Section through developing skin 

 of 15-mm. cat embryo. (C) Section through 85-mm. human embryo, showing three- 

 layered epidermis. (D) Human skin, eight months, showing well-developed stratum 

 corneum. (E) Early hair germ in human skin. (F) Later hair germ in human skin. 

 (G) Still later hair germ, showing hair cone, sebaceous-gland rudiment, and epithelial bed. 

 Observe that the hair cone arises as a result of the proliferative activity of the cells of 

 the epithelial or hair matrix which overlies the mesenchymal papilla. Compare with 

 fig. 273A. 



580 



