TACTILE HAIR OF THE WHITE RAT 15 



A brief review of some of the positions taken as to this nerve ring 

 band may be useful. Leydig ('59, p. 390) saw the ring but others 

 after him denied its existence. Bonnet ('78, p. 366) said the 

 fibers came from the outer plexus about the neck of the folhcle 

 and reached the ring in some unknown way, but Messenger ('90, 

 p. 401) thought it was composed of fibers from the nerve trunk 

 entering from below and Botezat declared that he saw fibers in 

 the ring from both sources ('03). Most authors agree that these 

 fibers end on the outer surface of the glassy layer, but Ranvier 

 says that they go through this layer ('75). As to their mode of 

 termination, few have been able to describe them. Ranvier said 

 they end in spatules ('75, p. 915) ; Botezat ('02) described them 

 as simple endings, thickened or flattened forms and Szymonowicz 

 ('09, p. 622) as forked endings. 



It is very easy to confuse the terminations of these fibers with 

 those of the branches of the longitudinal fibers which end many 

 of them here on the glassy layer. The fibers of the ring are 

 very fine and very easily broken in the preparations, so that it 

 is exceedingly difficult to be sure as to free endings or endings in 

 varicosities. Sometimes I have thought that I saw connections 

 between these delicate fibers and some plain muscle fibers which 

 surround the neck of the follicle but farther than this I can say 

 nothing about the endings here. I think the significance of this 

 ring has been over-estimated and for reasons which follow do not 

 agree with Messenger who says, "The annular nerve band is so 

 situated that when the pulvinus is not turgid tactile impulses 

 are little felt but when it- is turgid the slightest impact produces 

 a marked effect on the nerves surrounding the hair" ('05, p. 401). 

 Neither do I agree with Bonnet who thinks that the hypothesis 

 of a real intensification of power of perception through this nerve 

 ring is perhaps justified. Odenius' ('66) assertion that the ring 

 is confined to nocturnal animals has been refuted by others. 



Ringwulst. The structure of the ringwulst has been described 

 before. It springs out just beneath the superior swelling so that 

 all the large sensory fibers which terminate above it must pass 

 through it. Many of these nerves run close to the walls of the 

 follicle but others bend outward and pass through the ringwulst 



