516 



NERVOUS SYSTEM. 



or knotted coils. The nerve-fibres are medullated for a certain distance, 

 but their terminations are generally pale. The above is one form of these 

 corpuscles. Sometimes, however, the terminal bulbs 

 are oblong, and sometimes but a single nerve-fibre 

 penetrates the bulb and terminates in a simple, pale 

 filament. The principal forms of the terminal bulbs 

 are shown in Fig. 181. 



General Mode of Termination of the Sensor)/ 

 Nerves. The actual termination of the sensory 

 nerves upon the general surface and in mucous 

 membranes is still a question of some obscurity. 

 Although anatomists have arrived at a pretty definite 

 knowledge of the sensory corpuscles, it must be 

 remembered that there is an immense cutaneous and 

 mucous surface in which no corpuscles have as yet 

 been demonstrated ; and it is in these parts, endowed 

 with what may be called general sensibility, as dis- 

 tinguished from the sense of touch, that the moc 

 of termination of the nerves remains to be studied. 

 According to Kolliker, in the immense majorit 

 of instances the sensory nerves terminate in some 

 way in the hair-follicles. If this be true, it wil 

 account for the termination of the nerves in by fa 

 the greatest portion of the skin, as there are 

 parts in which hair-follicles do not exist ; but un- 

 fortunately the exact mode of connection of the 

 nerves with these follicles is not apparent. The 

 following seems to be all that is positively knowi 

 of the terminations of the nerves on the general sur- 

 face : 



Medullated nerve-fibres form a plexus in the 

 deeper layers of the true skin, and from this plex- 

 us, fibres, some pale and nucleated and others me 

 dullated, pass to- the hair-follicles, divide int 

 branches, penetrate into their interior and are ther 

 lost. A certain number of fibres pass to the non- 

 striated muscular fibres of the skin. A certah 

 the number pass to papillae and terminate in tactile coi 

 puscles, and others pass to papillae that have no 

 tile corpuscles. 



In the mucous membranes the mode of terming 

 tion is, in general terms, by a delicate plexus jus 

 of a 'neVve-"fib're. with two beneath the epithelium, coming from a submucoi 



terminal bulbs ; a. covering T 



of the terminal bulbs ; b, in- plexus analogous to the deep cutaneous plexus, li 



ternal bulb ; c, pale nerve- i . . 



fibre. certain membranes the nerves terminate m ena- 



bulbs, or corpuscles of Krause. In the cornea, according to the observatioi 



FIQ. 181. End-bulbs, or corpus- 



cles of Krause (Ludden). 

 A, three corpuscles of Krause 



from the conjunctiva of 

 actd'; magnltfedaoo 

 cte re with ^"ntrv 



senting a nerve-fibre and 

 fatty granulations in the in- 



m 



ial and 



B, terminal bulbs from the con- 

 junctiva of the calf, treated 



with acetic acid ; magnified 



300 diameters : 1, extremity 



2 f , a nerve-fibre with its 



bulb ; 2, double bifurcation 



