END-BULBS. 



147 



branching and interjimction of the fibril^ above described as resulting 

 from the division of the pale fibres or of the axis-cylinder of the white 

 fibres. The meshes of the net may be at first wider, and the threads, 

 or bundles of threads, larger, but from these, finer filaments forming 

 closer reticulations proceed, and then sometimes the nuclei become less 

 frequent, or disappear. Such networks are found in the skin, in various 

 parts of the mucous membranes, in the cornea, and in various other 

 parts : they will be most conveniently considered in the description of 

 the organs to which they belong. 



B. Sensory terminal organs. Three varieties of these are now 

 recognised, viz., end-tulhs, iactUc-corpiisdes, and Pacinian todies. 

 These have so far a common structure, that in all of them there 

 is an inward part or core {LinenJcoIhen, Germ.) of soft, translucent 

 substance ; an outer membranous capsule with pertaining corpuscles ; 

 and, finally, one or sometimes more nerve-fibres, pale and without dark 

 contours, which pass into the core and apparently end with a free, 

 usually somewhat swollen, or knobbed extremity. Thus agreeing in 

 their internal and probably essential structure, the terminal organs 

 differ chiefly, or at least most obviously, in their capsule, which, simple 

 in the end-bulbs, becomes highlj^ complicated in the Pacinian bodies ; 

 and therefore in the further account of them it will be convenient to 

 begin with the former, although the Pacinian bodies have been much 

 longer known. 



End-bulbs. — Noticed incidentally by Ivolliker, but first investigated 

 and recognised as distinct organs by W. Krause, who named them 

 Endkolhea. Their figure in man and apes 

 is usually spheroidal (fig. 99), but oblong in 

 some quadrupeds. They measure about -^j^oth 

 of an inch in diameter, but may exceed this 

 in length with a less breadth, when of an oval 

 shape. They have a simple outer capsule of 

 connective tissue, bearing nuclei, and within 

 this a core of clear soft matter, in which 

 specks resembling fat-granules become visible 

 after exposure to a solution of soda. To an 

 €nd-bulb there proceeds usually one, but some- 

 times two, or even three dark- bordered nerve- 

 fibres ; and sometimes an originally single 

 fibre divides into two or three immediately 

 before entering the corpuscle ; or several 

 branches of one fibre may each run into a 

 separate end-bulb. The fibre or fibres pass 

 into the core, lose their dark borders, and 

 appear to end, when their ends can be traced, 

 in a bulbous extremity or knob. The nerve- 

 fibre, wlicn about to enter the corpuscle, is 

 often much coiled, and this may be the case 

 too with its pale continuation within, which 

 contributes greatly to obscure its actual 

 termination. End-bulbs have been hitherto 



found in the conjunctiva over the sclerotic coat of the eye, and in 

 the mucous membrane on the floor of the mouth, t!ie lips, soft palate, 

 and tongue, being in these last-mentioned situations lodged in papilla?, 



Fig. 99. — Three Nerve- 

 end-bttlbs from the h0mait 

 Conjunctiva, treated with 

 acetic acid, magnified 300 

 diameters. 



1. With two nerve -fibres 

 forming coils within. '1. With 

 one nerve-fibre and fat-gra- 

 nules in the core. 3. Of an 

 oval figure ; termination of 

 nerve distinct. Nuclei on 

 the capsules of 1 and 2 (from 

 Kolliher, after a drawing by 

 Liiddeu). 



