678 ANATOMY OF THE MUZZLE OF ORN ITHORHYyCHUS, 



possessing present functional importance, and indicates that 

 they are no mere vestiges of some ancestral whiskers. 



The above described mode of termination of the tiljres at the 

 base of the follicle is not peculiar. Dietl* i-ecorded and figured 

 somewhat similar endings in the root sheath of the sensitive hairs 

 of the ox, cat, and dog. He described the nerve fibres as pene- 

 trating the hyaline layer of the dermic sheath and ending amongst 

 the epithelial cells of the outei'most two layers of the outer root 

 sheath in knobbed ("knopfformig") swellings. Dietl was uncertain 

 whether they were indeed terminal. Bonnetf confirmed Dietl's 

 observati(ms and extended them to the sensitive hairs of a variety 

 of domestic animals. He described the nerves as ending in the 

 deeper layers of the epithelium of the outer root sheath in pale, 

 knobbed, finely granular expansions of the axis-cylinder. These 

 are situated in a very distinct capsule formed by the primitive 

 sheath. Bonnet considered these expansions of the axis-cylinder 

 as identical with the "Tastzellen" described by Merkelj as occur- 

 ring in the same situation, but, as we think justlv, denies their 

 cellular character. 



If anyone will compare figs. 1-1 and 15 of Plate xix., and fig. 12 

 of Pla.te xviii., in Bonnet's paper, with those accompanying this 

 paper, he will find it impossible to doubt that the structures are 

 identical in character. The first of these three figures of Bonnet 

 represents a vertical section of the root sheath of a sensitive 

 hair ivoxw the horse stained with osmic acid, the second a similar 

 preparation from the snout of the pig. The third is also fron\ the 

 snout of the pig, and represents the base of an epithelial d(jwn- 

 gi'owth stained by Lowits' gold chloride process, and might indeed 

 well enough I'epresent a patch of one of our gold chloride prepara- 

 tions of the nerve endings in the bulb of the sweat-duct. 



* Untersuchimgen iiber Tasthaare II. 8itz«ngsbericlite der k. Akad. d. 

 VViss. Wien. Mat. Naturwiss. Klasse Ixvi. Bd., iii. Abtheil. 1872. 



+ " Stiulien iiber die Innervation der Haarhalge der Hausthiere." 

 Morph. Jahrbuch von Gegenbaur, Bd. iv. 1878. 



