SYMPATHETIC NERVE. 



441 



so that he believes each of them is connected 

 with one of these bodies. 



Invertebrata. The ganglionic corpuscles 

 in the ganglia of the invertebrata appear to 

 be the same in their essential characters as 

 those of the vertebrate animals. Will* re- 

 cognises two kinds of ganglion-corpuscles in 

 the lower animals. The one he describes as 

 consisting of a membrane and nucleus, the 

 space between the two being occupied by a 

 clear transparent fluid, which becomes granular 

 on the addition of water ; in the other variety 

 there are imbedded in the clear transparent 

 fluid numerous small round cells in which no 

 nucleus is visible. The cells belonging to the 

 former variety have always but one process 

 attached to them which consists of a single 

 tube, presenting no division so far as it can 

 be traced, and thus corresponding to the uni- 

 polar variety of corpuscle. In the second 

 kind of corpuscles there are several such pro- 

 cesses present ; the processes attached to 

 some of these cells all run in one direction ; 

 in others they pass off at either extremity 

 and run in opposite directions. In the leech, 

 according to Bruch-f-, there are also two kinds 

 of ganglion corpuscles. The one variety are 

 round and are apolar ; the others are con- 

 nected with nerve-fibres. The latter are situ- 

 ated towards the lower part of the ganglia, 

 and are more numerous than the former: they 

 are more or less pyriform, their wider ex- 

 tremity being directed outwards ; their nar- 

 rower, terminating in a process, is directed 

 towards the ganglia and the nervous cord. 

 Peripherical ganglia, consisting of from one 

 to six or seven cells, are always found at the 

 points where the branches of the nerves di- 

 vide. Ganglionic corpuscles were also seen 

 by him in the interior of the nerve-tubes, and 

 corresponding to the view taken by Bidder J 

 of the constitution of the bipolar ganglionic 

 corpuscle. Apolar and unipolar cells have 

 also been described by Hannover and Leydig 

 in several other invertebrate animals. 



From the fact that in such animals as the 

 torpedo and ray, where the ganglionic cor- 

 puscles are easily isolated from each other, 

 they are all found to belong to the bipolar 

 variety, Wagner, Robin, and Bidder believe 

 that all the ganglionic corpuscles in other 

 animals are also bipolar. Kolliker, on the 

 other hand, while he admits that the bipolar 

 cell is most frequent in the fish, maintains 

 that the opposite is the case as regards the 

 higher animals, most of the corpuscles in 

 them belonging either to the apolar or uni- 

 polar varieties; and so far as actual observa- 

 tion goes, the views of Kolliker seem to be 

 perfectly correct, inasmuch as, while apolar 

 and unipolar cells are very frequently seen in 

 these animals, the bipolar variety has been 

 seen very seldom. It is possible, however, 

 that many of these unipolar and apolar cells 

 may, as Wagner and Bidder, &c. hold, be 

 really bipolar cells, one or both nerve-tubes 



* Miiller's Archiv. 1844, p. 76. also in Canslatt's 

 Jahresbericht, 1847. 



t Ibid. t Ibid. 



having been broken off during the manipula- 

 tion required for submitting them to examina- 

 tion. In the spinal ganglia of the ray the 

 cells are very easily isolated from each other, 

 whereas in the abdominal ganglia it is very 

 difficult, owing to the amount of surround- 

 ing fibrous structure, to isolate them. Now 

 in the former only bipolar cells are seen, 

 whereas in the latter, most of the cells, when 

 isolated, appear to be unipolar and apolar, 

 although it would appear from the observa- 

 tions of Wagner and others, that they are all 

 bipolar, like those in the spinal ganglia. In 

 the higher animals, especially in the mam- 

 malia, the ganglionic corpuscles are isolated 

 from one another with as much difficulty as 

 those in the abdominal ganglia of the skate ; 

 and hence the probability that many at least 

 of the unipolar and apolar cells which are seen 

 in them, belong to the bipolar variety in 

 reality. On the other hand that apolar and 

 unipolar ganglion -corpuscles really exist, and 

 that too in considerable numbers, in the gan- 

 glia of the higher animals, and also in those 

 of the invertebrata, seems to be shown by 

 numerous observations on the smaller gan- 

 glia, where no preparation is required, and 

 where, consequently, the above source of 

 fallacy cannot intervene. In the sympathetic 

 cord of the frog, according to Valentin *, 

 groups of ganglionic vesicles may be observed, 

 without a single nerve-fibre connected with 

 them : Ludwig f has also observed in the au- 

 ricle of the frog's heart small ganglia in which 

 there were eleven gangtionic corpuscles, and 

 only four or five nerve-tubes ; in a nerve 

 passing to the bladder of the frog, and con- 

 sisting of only two nerve- fibres, Valentin 

 counted as many as seven ganglionic cor- 

 puscles, | while another, consisting also of 

 only one or two nerve-fibres, was surrounded 

 by twenty-four ganglionic corpuscles. 



In accordance with the view adopted by 

 Wagner, that all the ganglionic corpuscles are 

 bipolar, the nerve-tube connected with either 

 extremity of the cell running in opposite 

 directions, one towards the centre, the other 

 peripherically, Robin believes that all nerve- 

 tubes arise exclusively from the brain and 

 spinal cord ; neither the spinal ganglia nor 

 those of the sympathetic give origin to nerve- 

 tubes; the ganglion-cells are merely organs 

 developed upon the nerve-tubes, between 

 their central and peripherical termination, and 

 several such may be present on a single nerve- 

 fibre during its course. From what has been 

 already stated, however, it seems probable 

 that unipolar as well as bipolar cells exist in 

 the ganglia, and consequently that nerve- 

 tubes do originate in them. That nerve-fibres 

 arise in the ganglia, is further shown by the 

 accurate measurements of Volkmann and 

 Bidder of the nerves passing to and those 

 leaving the ganglia. The ciliary, Gasserian, and 

 spinal ganglia in the frog were found by them 

 to give off a far greater number of fine nerve- 



* Lehrbuch der Physiologic; Braunschweig, 

 1848 ; band ii. p. 602. 



f Mailer's Archiv. 1848, p. 142. 



