TACTILE HAIR OF THE WHITE RAT 13 



acteristic position. In the superior root swelling where they 

 attain their greatest size they usually lie vertical to the long axis 

 of the hair and beneath the cell body. The flattened surface of 

 the menisque is somewhat parallel to the surface of the skin. 

 Near the glassy layer, however, the position is almost at right 

 angles to the surface of the skin and parallel to the long axis of 

 the hair. This is due no doubt to the resisting power of this 

 layer. In the lower portions of the follicle — for these endings 

 cover the whole of the follicle contrary to the opinion of many 

 of those who made the earlier studies of the endings — they are 

 more varied in position but may often be seen parallel to the 

 axis of the hair shaft. Ranvier (75) first described these struc- 

 tures truly and recognized them as the touch cells which Merkel 

 ('76) had previously found in other parts of the skin. Subse- 

 quent investigations have shown that the fiber does not end in 

 the cells, as Merkel first thought. It is generally believed now 

 that this cell is simply a modified epithelial cell which may serve 

 as a protective cushion for the nerve expansion and possibly 

 help to increase or modify the pressure stimulus. 



Besides the nerves which end in this way, fibers leave the main 

 bundle the whole length of the follicle, run to the glassy layer 

 and arborize upon its surface or end in free or flattened spg^tulate 

 endings, so that the entire outer surface of the glassy layer is 

 covered with a fine nerve plexus. Among these fibers are some 

 which penetrate the glassy layer and end between the epithelial 

 cells of the outer root sheath. Tello ('05) and Ostroumow ('95, 

 p. 914) say that these fibers are of a different order from those 

 which end in menisques within the glassy layer. That they usu- 

 ally appear smaller and not so heavily medulated, at least not 

 so deeply stained, is true, but that they are different in origin or 

 function seems doubtful. Among those fibers which end in 

 menisques occasionally one is found which forms several small 

 menisques before piercing the glassy layer; again from menisques 

 within the glassy layer go off little fibrils which run between the 

 cells of the outermost layer of the outer root sheath and end 

 intra-epithehally or arborize about these cells, as Merkel first 

 described; but besides these one. may see at times nerves which 



