STRUCTURE OF THE ORGANS OF TOUCH. 



827 



The Sense of Touch. 



424. TERMINATIONS OF SENSORY NERVES. 1. The touch-corpuscles of Wagner and 



Meissner lie in the papillae of the cutis vera ( 283), and are most numerous in the palm of the 

 hand and the sole of the foot, especially in the fingers and toes, there being about 21 to 

 every square millimetre of skin, or 108 to 400 of the papillae containing blood-vessels. They 

 are less abundant on the back of the hand and foot, mamma, lips, and tip of the tongue, rare 

 on the glans clitoridis, and occur singly and scattered on the volar side of the fore-arm, even in 

 the anthropoid apes. They are oval or elliptical bodies, 40-200 ^ long [^^ in.], and 60-70 fi 

 broad [--^ to -$fo in.], and are covered externally by layers of connective-tissue arranged 

 transversely in layers, and within is a granular mass with elongated striped nuclei (figs. 608, 



609, e). One to three medullated 

 nerve-fibres pass to the lower 

 end of each corpuscle, and sur- 

 round it in a spiral manner two 

 or three times ; the fibres then 

 lose their myelin, and, after 

 dividing into 4 to 6 fibrils, branch 

 t .JgR within the corpuscle. The exact 



Fig. 608. Fig. 609. 



Fig. 608. Vertical section of the skin of the palm of the hand, a, blood-vessels ; b, papilla 

 of the cutis vera ; c, capillary ; d, nerve-fibre passing to a touch-corpuscle ; /. nerve- 

 fibre divided transversely ; e, Wagner's touch-corpuscle ; g, cells of the Malpighian layer 

 of the skin. Fig. 609. Wagner's touch-corpuscle from the palm, treated with gold 

 chloride ; n, nerve-fibres; a, a, groups of glomeruli. 



mode of termination of the fibrils is not known. Some observers suppose that the transverse 

 fibrillation is due to the coils or windings of the nerve-fibrils ; while according to others, 

 the inner part consists of numerous flattened cells lying one over the other, between which 

 the pale terminal fibres end either in swellings or with disc-like expansions, such as occur in 

 Merkel's corpuscles. 



[These do not contain a soft core such as exists in Pacini's corpuscles. The corpuscles appear 

 to consist of connective-tissue with imperfect septa passing into the interior from the fibrous 

 capsule. After the nerve-fibre enters it loses its myelin, and then branches, while the branches 

 anastomose and follow a spiral course within the corpuscle, finally to terminate in slight 

 enlargements. According to Thin, there are simple and compound corpuscles, depending on 

 the number of nerve-fibres entering them.] 



Kollmann describes three special tactile areas in the hand : (1) The tips of the fingers with 

 24 touch-corpuscles in a length of 10 mm. ; (2) the three eminences lying on the palm behind 

 the slits between the fingers, with 5 '4-2 "7 touch-corpuscles in the same length ; and (3) the 

 ball of the thumb and little finger with 3*1-3 "5 touch -corpuscles. The first two areas also 

 contain many of the corpuscles of Vater or Pacini, while in the latter these corpuscles are fewer 

 and scattered. In the other parts of the hand the nervous end-organs are much less developed. 



