NEEVE-FIBRES 



1053 



The Author believes that it may be stated as a general fact, that in 

 both the motor and the sensory nerve-tubes, as they approach their 

 terminations in the muscles and in the skin respectively, the 

 protoplasmic axis-cylinder is continued beyond its envelopes, 

 often then breaking up into very minute fibrillae, which inosculate 

 with each other, so as to form a network closely resembling that 

 formed by the pseudopodial threads of Rhizopods. Recent observers 

 have described the nbrillae of motor nerves as terminating in 

 ' motorial erid-plates ' seated upon or in the muscular fibres ; and 

 these seem analogous to the little ' islets ' of sarcodic substance into 

 which those threads often dilatte. Where the skin is specially 

 endowed with tactile sensibility we find a special papillary 

 apparatus, which in the skin may be readily made out in thin 

 vertical sections treated with solution of soda (fig. 790). It was 

 formerly supposed that all the cutaneous papillae are furnished with 

 nerve-fibres, and minister to sensation ; but it is now known that a 

 large proportion (at any rate) of those that are furnished with loops 

 of blood-vessels (figs. 775, p, 798), being destitute of nerve-fibres, 

 must have for their special 

 office the production of 

 epidermis ; whilst those 

 which, possessing nerve- 

 fibres, have sensory func- 

 tions, are usually destitute 

 of blood-vessels. The 

 greater part of the interior 

 of each sensory papilla 

 (fig. 790, c c) of the skin 

 is occupied by a peculiar 

 ' axile body,' which seems 

 to be merely a bundle of 

 ordinary connective tissue, 

 whereon the nerve-fibre 

 appears to terminate. The 

 nerve - fibres are more 

 readily seen, however, in 

 the ' fungiforin ' papillae of 



the tongue, to each of which several of them proceed ; these bodies, 

 which are very transparent, may be well seen by snipping off minute 

 portions of the tongue of the frog ; or by snipping off the papillae 

 themselves from the surface of the living human tongue, which can 

 be readily done by a dexterous use of the curved scissors, with no 

 more pain than the prick of a pin would give. The transparence 

 of these papillae also is increased by treating them with a weak 

 solution of soda. Nerve-fibres have also been found to terminate 

 on sensory surfaces in minute ' end-bulbs ' of spheroidal shape and 

 about -(-jToth of an inch in diameter, each of them being composed 

 of a simple outer capsule of connective tissue, filled with clear 

 soft matter, in the midst of which the nerve-fibre, after losing its 

 dark border, ends in a knob. The ' Pacinian corpuscles,' which are 

 best seen in the mesentery of the cat, and are from ^th to jLth of 



FIG. 790. Vertical section of skin of finger, show- 

 ing the branches of the cutaneous nerves, a, b, 

 inosculating to form a plexus, of which the ulti- 

 mate fibres pass into the cutaneous papillae, c c. 



