770 



CUTANEOUS SENSATIONS 



[CH. Mil. 



locomotor ataxy, which is a disease of the sensory nerve-units, and 

 remain healthy in infantile paralysis, which is a disease of the 

 motor cells of the anterior horn of the cord (Batten). 



m.h.b. 



PIG. 475. Neuromuscular spindle, c., Capsule; n.tr., nerve trunk; m.n.b., motor nerve bundle; 

 pl.e., plate-ending; pr.e., primary nerve-ending; s.e., secondary ending. (After Ruflini.) 



In addition to the 



special end-organs, sensory fibres may 

 terminate in plexuses of fibrils, as in 

 the subepithelial and the intra-epithelial 

 plexus of the cornea (fig. 476) and 

 around the hair follicles in the skin 

 generally (see fig. 392, p. 607). In some 

 cases the nerve-fibrils within a stratified 

 epithelium end in crescentic expansions 

 (tactile discs') which are applied to the 

 deeper epithelium cells. These are well 

 seen in the skin of the pig's snout. 



Localisation of Tactile Sensations. 



The localisation of a tactile sensation 

 is of two kinds, absolute and relative. 

 We can localise a touch on the arm 

 absolutely by indicating the exact spot 

 which has been touched, or we may 

 localise it relatively to another spot on 

 the arm which is simultaneously or suc- 

 cessively touched. Generally speaking, 

 the delicacy of these two kinds of locali- 

 sation is similarly variable in different 

 parts of the body. 



The "local signature" (p. 762) of 

 cutaneous sensations may be easily inves- 

 tigated by touching the skin, while the 

 eyes are closed, with the points of a pair 

 of compasses, and ascertaining how close the points may be brought 



FIG. 476. Vertical section of rabbit's 

 cornea, stained with gold chloride. 

 The nerves, n, terminate in a plexus 

 uuder and within the epithelial 

 layer, e. 



