PAR VAGUM. 



881 



(Fi 



One of the follicular nervous organs of the electrica 

 . torpedo. 



a, branch of fifth pair of nerves ; b, twigs going 

 to the organ and passing through cc, the fibrous 

 band ; d, the nerve as it lies on e, the granular 

 mass ; f and g, the inner and the outer capsules 

 containing fluid ; k anastomosing filament from the 

 preceding follicle ; /, anastomosing filament to the 

 succeeding follicle. Much magnified and slightly 

 compressed. From Savi. 



twig is derived from the fifth pair and passes 

 first through a slit in the tendinous band. After 

 passing this aperture it bends underneath the 

 granular mass, and again emerges at the base 

 of the follicle, but at the opposite side from 

 that at which it entered. It is remarkable that 

 the nerve is much thinner at its exit, and re- 

 duced to an exceedingly delicate filament (/), 

 which proceeds along the tendinous band to 

 the next follicle, penetrating its wall and join- 

 ing its nerve at the point of its flexion under 

 the granular mass (/c). 



" On examining under the microscope the 

 rounded granular mass, made flat by the com- 

 pressor, and after the removal of the membranes 

 of the follicle, we see the nerve running length- 

 wise over it from end to end, the anastomosing 

 branch coming from the preceding follicle (/c) 

 and the very delicate filament which proceeds 

 to that next in order (I). We further remark 

 that the nerve of the follicle, in its course along 

 the granular mass, gives oft' a great number of 

 elementary fibres, which disseminate themselves 

 through the mass and thus reduce the nerve to 

 so small a size. Sometimes I have fancied that 

 these fibres formed loops and returned ; but I 

 have never obtained a clear view of their termi- 

 nation. I am no less doubtful regarding the 

 course of the elementary fibres of the anasto- 

 mosing branch coming from the preceding 

 follicle. Sometimes I have seen these fibres 

 return towards the slit in the tendinous band 

 and rejoin the nerve in order to regain the 

 centre. In other cases I have seen these fibres 

 pursue their primitive direction, and pass on 

 with the rest towards the opposite end of the 

 granular mass. Hence I imagine that the fibres 

 of the anastomosing bundle do not all follow 

 the same course, and that while some advance 

 into the granular mass, others turn back towards 



VOL. III. 



the centre through the slit in the fibrous band." 

 " It occasionally happens that two nervous 

 twigs pass from the main branch to the same 

 follicle. When this happens, there are always 

 two distinct granular masses." M. Savi then 

 describes accurately the arrangement of the 

 several series of these follicles in the torpedos 

 which he examined, an account of which is not 

 necessary for our present purpose. In one 

 example he found that the follicles amounted in 

 all to two hundred and fourteen. 



We cannot adduce these remarkable and 

 peculiar structures as at present throwing any 

 light on the function of the Pacinian corpuscles, 

 since we must confess with M. Savi that as yet 

 we are entirely ignorant both of their real nature 

 and use. Nevertheless the resemblance is such 

 as, it is hoped, will warrant the introduction of 

 the preceding account, which is new in this 

 country, and very interesting in itself. It is 

 unnecessary to recapitulate the several points of 

 similarity and difference, which, after the de- 

 tailed description of each now offered, may be 

 readily apprehended by the reader himself. 



It only remains that we should direct atten- 

 tion to the very admirable memoir of Henle 

 and Kijlliker on this subject. They corrobo- 

 rated the principal results of Pacini, and added 

 many most valuable observations which the use 

 of higher powers of the microscope and perhaps 

 greater experience in research had enabled them 

 to make. These observations M. Pacini has 

 recently informed me he has himself almost 

 entirely confirmed. An excellent abstract of 

 their labours appeared in theBritish and Foreign 

 Medical Review for January, 1845, and in the 

 following April Dr. Todd and myself gave an 

 account of these structures, drawn up from origi- 

 nal observations and containing some new results, 

 though on the whole confirmatory of those 

 previously published. See the PHYSIOLOGICAL 

 ANATOMY AND PHYSIOLOGY OF MAN, vol. i. 

 p. 395. 



It is right to add that MM. A. G. Andral, 

 Camus, and Lacroix, met with these bodies in 

 1833, and that they were noticed subsequently 

 by Cruveilhier and Blandin in their respective 

 works on descriptive anatomy, bnt without any 

 real light being thrown on their nature or 

 internal structure. 



( William Bowman.) 



PAR VAGUM NERVE. (HUMAN ANA- 

 TOMY.) (N(rvus Vagus; Pneumogastric ; 

 part of the sixth pair of nerves of the older 

 anatomists; one of the three divisions of the 

 eighth pair in the classification of Willis; the 

 ninth pair of Andersch ; the tenth pair of 

 Sbmmerring ; the moi/en sympathique of Win- 

 slow.) The par vagum, like the other cerebro- 

 spinal nerves, consists of two nerves exactly 

 similar at their origin, and placed on different 

 sides of the mesial line of the body. It has a 

 very long course, passing down the neck, and 

 through the thorax to the upper part of the 

 abdomen, is distributed upon numerous and 

 dissimilar organs, and anastomoses very freely 

 and extensively with the sympathetic and vari- 

 ous cerebro-spinal nerves. It is the chief nerve 



3 L 



