580 DES. GEORGE A.ND FRANCES E. HOGGA.N ON 



mic plexus in general. Tliat the sense of toucli does not belong 

 to this system we would argue from the fact that the piece of 

 down, which excites distinct tactile sensations on the hairs on 

 the back of the hand, may be applied with equal force to the 

 sensitive cornea without conveying the sense of touch, although 

 it may readily excite pain there, if allowed to remain in mechani- 

 cal contact with it ; and we know equally well that, although the 

 epithelial surface of the cornea is more plentifully supplied with 

 free intraepidermic nerve-endings than perhaps any other part 

 of the body, the rubbing of the eyelid does not make itself felt 

 as a tactile sensation, although, in the absence of that rubbing, a 

 very distinct sensation of pain makes itself felt. 



That Professor Merkel should have been led into considering 

 the nerve-cells and free endings as belonging to two different 

 systems, is perfectly explicable from the fact that in those re- 

 searches he used only osmic acid, which fails to show the intra- 

 epidermic free endings ; but it is curious to find that so great an 

 adept with the gold process as Professor Ranvier should have 

 failed to trace the connexion between the two elements. 



JRanvier^s Morphological Ohjections to MerTceVs views. 

 Of the investigators in this special department who have suc- 

 ceeded Professor Merkel and repeated his examinations. Professor 

 Eanvier appears to be the only one who takes direct exception 

 to Merkel's morphological conclusions, while appearing to accept 

 his physiological ones ; but even he has failed to observe the con- 

 nexion (and the cause of it) of the nerve-cells with the free 

 intraepidermic endings, which lies at the root of the whole question. 

 Professor E-anvier's morphological criticism extends to all the four 

 structures or tactile organs described by Merkel — to the touch- 

 bodies in Birds, the touch-corpuscles in Man, the tactile cells in 

 the feelers, and the tactile cells in the epidermis, which we are 

 now considering. lu all of these structures Eanvier rejects the 

 interpretations given by Merkel, and applies instead a description 

 which is the result of his own investigations into them ; that is 

 to say, instead of admitting them to be tactile nerve-cells, he holds 

 that there are two component elements in each, the cellules du tact 

 of Merkel and the "cUsqtces tactiles'" which he had previously de- 

 scribed in the touch-bodies of Birds. We have already given Pro- 

 fessor Eanvier's views on the terminations in the feelers ; and we 

 do not intend to enter further into the consideration of the touch- 



