466 



NERVOUS SYSTEM 



provided with bloodvessels ; so that the papillae of the hand, may be 

 properly divided into vascular and nervous. 



The form of the tactile corpuscles is oblong, with the long diameter 

 in the direction of the papillae. Their length is -%^-Q to ^-Jo" of an inch 

 (66 to 100 /x). In the palm of the hand they are ^-Q to T |Q of an inch 

 (100 to 165 7-t) long, and -^Q- to -g^- of an inch (45 to 50 /-t) in thickness. 

 They usually are situated at the summits of the secondary eminences of 

 the compound papillae. They consist of a central bulb of homogeneous 

 or slightly granular connective-tissue substance, harder than the central 

 bulb of the corpuscles of Vater, and a covering. The covering is com- 

 posed of connective tissue with a few fine elastic 

 fibres. One, two, and sometimes three or four 

 dark-bordered nerve-fibres pass from the subcu- 

 taneous nervous plexus to the base of each cor- 

 puscle. These surround the corpuscle with two 

 or three spiral turns, and they terminate in pale 

 extremities on the surface of the central bulb. 



End-bulbs. Under this name, a variety of 

 corpuscles has been described by Krause as ex- 

 isting in the conjunctiva covering the eye and in 

 the semilunar fold, in the floor of the buccal 

 cavity, the tongue, the glans penis and the cli- 

 toris. They bear some analogy to the tactile 

 corpuscles, but they are smaller and more simple 

 in their structure. They form rounded or oblong 

 enlargements at the ends of the nerves, which are 

 Fig. 105. Corpuscle of composed of homogeneous matter with a delicate 

 Krause from the human con- i nves tment of connective tissue, lined with endo- 



junctiva (Dogiel). 



thelial Cells The Y measure ^ to fa of an 



In the parts 



.11 .11 



provided with papillae, they are situated at the 

 summits of the secondary elevations. The arrangement of the nerve- 

 fibres in these corpuscles is very simple. One, two, or three medullated 

 fibres pass from the submucous plexus to the corpuscles. The investing 

 sheath of the fibres is here continuous with the connective tissue cover- 

 ing of the corpuscle, and the nerve-fibres pass into the corpuscle, break 

 up into two or three divisions, and terminate in convoluted or knotted 

 coils. The nerve-fibres are medullated for a certain distance, but their 

 terminations are 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. 



, endothelial envelope; 



b, nucleus of a connective- inch (25 to ioo JJL) in diameter. 



tissue cell: c, nerve-fibre. 



