234 



THE JOURNAL OF PHARMACOLOGY. 



about one-third mm. in length. The medulla, which is ver}^ narrow at 

 the root, increases rapidly in thickness and at but several ram. above the 

 base, where the hair has a thickness of 80 to 90/.*, it will be"50,a thick. 

 For this reason the fibrous layer forms but a very thin cylinder. The 

 cross section is round. The epiderm consists of scales 15 p. high, broader 

 transversely, whose fore edge seems scarcely thickened, but distinctly out- 

 lined. The edge is not toothed, but unevenly sinuous. The fiber long re- 

 tains this character, but increases to 100 // in thickness, the medulla be- 

 coming 80 ,« thick. The medullary cells are thick-walled, narrow and 

 broader than high. Towards the middle the hairs again grow narrower 

 and attain their greatest thickness just before the tip, measuring there 

 about 12,0 !>-. There the cortical layer is, relatively, narrowest — 5 /> ; the 



Ui-A 



-'i 



A 



Fig. 9. 



Fig. 10. 



Fig. 9. The middle of two grannen hairs, a, cow's hair ; b, goat's hair. In a are seen the charac- 

 teristic transverse fissures q in the medulla m, which are filled with air. In a and b the fiber fissures 

 are shown at/and the imbricated epidermal scale at e. 350. 



Fig. 10. Mohair or angora wool. Grannen hairs without medulla. Epidermal scales care very 

 thin, imbricated and a toothed front edge. The hairs are coarsely striated with large fissures f. a. 

 first quality ; b, inferior quality. 350. 



medullary cylinder consists of six to ten rows of medullary cells, and the 

 hair (partly due to liming, incineration) is very brittle and cracks easily. 

 Towards the tip the medulla attenuates rapidly, the cylinder finally has 

 but one row of long cells, medullary isles following this, and when the 



