THE NERVES. 69 



they have also been described by Rauber as connected with the nerves of the 

 joints, and with the nerves lying between many of the muscles of the trunk 

 and limbs. Each of these corpuscles is attached to and incloses the termination 

 of a single nerve. The corpuscle, which is perfectly visible to the naked eye 

 (and which can be most easily demonstrated in the mesentery of a cat), consists 

 of a number of concentric layers of cellulur tissue, between which Todd and 

 Bowman have figured capillary vessels as running. The nerve, at its entrance 

 into this body, parts with its white substance, and the axis-cylinder runs 

 forwards in a kind of cavity in the centre of the corpuscle to terminate in a 

 rounded end or knob, sometimes bifurcating previously, in which case each 

 branch has a similar termination. Grandry, who has examined these corpus- 

 cles with very high magnifying powers, describes the axis-cylinder as exhibit- 

 ing a very well marked fibrillar structure, and the bulbous end as consisting 

 of a mass of granules into which the fibrils run, diverging as they approach it. 

 The investing capsules are from thirty to sixty in number, the outer being 

 more separated from each other, as if by a clear fluid, while the inner are 

 closely applied together. Schultz calls attention to the striking resemblance in 

 all essential particulars between these corpuscles and Krause's end-bulbs above 

 described. 1 



In the special organs the nerves end in various ways, which hitherto are not 

 perfectly known. 



Hoyer and Cohnheirn have described the nerves of the cornea as terminating 

 in primitive fibrillae, which run between the cells forming the pavement-epithe- 

 lium of that membrane, and end on its free surface. This, however, is doubted 

 by Hulke, 2 who has only succeeded in tracing them as far as the middle tier 

 of the epithelial cells. Schultze discovers in the olfactory mucous membrane, 

 lying between the cells of its epithelium, spindle-shaped cells, each possessing a 

 central and a peripheral process the central process being, according to him, 

 continuous with a primitive fibril of the olfactory nerve, and the peripheral 

 process either ending on the free surface of the epithelium, as is the case in men, 

 mammals, and fishes, or in some other animals prolonged into a long stiff hair. 

 These cells he has denominated "olfactory cells;" and similar cells have been 

 described by Axel Key, Schwalbe, and Loven, in the papilla circumvallatse of 

 men, and the fungiform papillae of the frog ("taste-cells"). The fibres also of 

 the optic nerve have, according to Schultze, a similar connection with the cells 

 ("sight-cells") of the retina; and cells somewhat similar, and connected with 

 processes that pass through the epithelium, are to be found on the nerve fibrils 

 of the auditory nerve, in the membranous labyrinth ("hearing-cells"). 



The terminations of the nerves in the hair-bulbs are probably to be found in 

 the papillae at their root, as is also the case in the teeth. In glands the nerves, 

 according to Pfliiger, are connected with the cascal commencements of the 

 gland tubes at least he has described this arrangement in the salivary glands, 

 and thus he is led to regard the nuclei of these caecal pouches as the termina- 

 tions of the nerves. 



Motor nerves are to be traced either into unstriped or striped fibres. 



In the unstriped fibres it appears from the researches of Beale, Frankem 

 haiiser, and Julius Arnold, that the ultimate fibrils of the nerves form plexuses 

 at the junctions of the branches of which small nuclear bodies are situated. 

 These nuclei are regarded by Arnold as the real terminations of the nerves, 

 for although he agrees with Frankenhaiiser in stating that the nervous filaments 

 penetrate the muscular fibres, and enter into relation with the granular con- 

 tents of their nuclei, he traces the filaments back again from that point to the 

 nuclei situated at the junctions of the nervous plexuses, in the connective 

 tissue of the muscular fibres. 



1 Strieker's Handburh, p. 123. 



a Lectures on the Histology of the Eye, at the Royal College of Surgeons, June, 1869. 



