4:0 NERVOUS SYSTEM. 



to have an important function in connection with the sense 

 of touch. 



"We have already treated of the structure of the skin in 

 another volume, 1 where we have seen that the largest pa- 

 pillae, measuring from ^ to -g-J-g- of an inch in length, are 

 found on the hands, feet, and nipples, precisely where the 

 tactile corpuscles are most abundant. Corpuscles do not 

 exist in all papillae, and are found chiefly in those called com- 

 pound. In the space of about -^ of an inch square on the 

 third phalanx of the index-finger, Meissner counted four 

 hundred papillae, in one hundred and eight of which he found 

 tactile corpuscles, or about one in four. In the same space on 

 the second phalanx, he found forty corpuscles ; on the first 

 phalanx, fifteen ; eight on the skin of the hypothenar emi- 

 nence ; thirty-four on the plantar surface of the ungual phalanx 

 of the great-toe ; and seven or eight in the skin on the middle 

 of the sole of the foot. In the skin of the forearm, the cor- 

 puscles are very rare. 2 Kolliker states, also, that the tactile 

 corpuscles usually occupy special papillae, which are not pro- 

 vided with blood-vessels ; so that the papillae of the hand 

 may be properly divided into vascular and nervous. 



The form of the tactile corpuscles is oblong, with their 

 long diameter in the direction of the papillae. Their length 

 is from -g-J-g- to -^-5- of an inch. In the palm of the hand, they 

 are from -%^ to y-J-g- of an inch long, and from -g-g-^- to -g-j-g. of 

 an inch in thickness. 3 They are generally situated at the 

 summits of the secondary eminences of the compound pa- 

 pillae. 



It is almost certain that the tactile corpuscles consist of 

 connective-tissue elements, with nerve-fibres making a few 

 spiral turns on their surface and finally disappearing in their 

 substance. This view is most ably supported by Kolliker, in 

 opposition to the proposition advanced by Eouget, that the 



1 See vol. iii., Excretion, p. 115. 



2 KOLLIKER, Elements d'histologie Jiumaine, Paris, 1868, p. 139. 



3 KOLLIKER, op. cit., p. 138. 



