NERVE END ORGANS IN SKIN. 



557 



They are oval, from 1.5 to 2.5 mm. (^ to ^ inch) long, 

 by about half that width, and have a whitish translucent 

 appearance, with a more opaque centre. When magnified 

 ^ach is found to consist of a core, surrounded by many 

 concentric capsules, b. A nerve-fibre, a, enters at one end, 

 and its axis cylinder, c, runs through the core to near the 

 other, where it terminates in one or two little knobs, or a 

 number of fine branches. 



The tactile corp u scles lie in papillae of the dermis, and 

 are oval and about .08 mm. (-^ inch) in length. They 

 contain a soft core, enveloped by a connective-tissue cap- 



FIG. 152. Dermic papillae with tactile corpuscles. A, a corpuscle with four 

 nerve-fibres; a, corpuscle; 6 and c, nerve-fibres. B, papilla made transparent 

 with acetic acid to show tactile corpuscle within ; o, proper tissue of the papilla; 

 fc, tactile corpuscle ; c, entering nerve, d, e, nerve-fibres twining round the cor- 

 puscle. C, a papilla, containing a tactile corpuscle, seen in optical transverse 

 -section. 



sule, and separated into several masses. Two, three, or 

 more nerve-fibres go to each corpuscle and appear to end 

 in plates lying between each of the segments of the core. 

 Tactile corpuscles are numerous in the skin of the hand 

 and foot, but are rare elsewhere. This limited distribution 

 4>ver the surface militated against the belief that they were 

 tactile end organs; but it has lately been found that simpler 

 bodies, the touch-cells, of the same essential structure but 

 receiving only one nerve-fibre each, are distributed all over 

 the skin; the more complex, and probably more irritable, 

 form being found where the epidermis is especially thick. 



