676 SYMPATHETIC AND OTHER SYSTEMS OF NERVES. 



AUTOMATISM OF PERIPHERAL GANGLIA. 



It perhaps hardly needs to be pointed out that, if the peripheral 

 ganglia are devoid of automatism, no essential difference is thereby 

 established between their nerve cells and those of the central nervous 

 system. For many nerve cells on the central nervous system have, so far 

 as we know, no automatic action ; and in other cases in which automatic 

 action appears to exist, it is uncertain how far it is simply apparent, 

 and due in reality to afferent impulses. 



The experiments to which we may look to throw light on the 

 question as regards those nerve cells which are normally in tonic 

 activity, fall into three classes : 



1. We may cut the fibres running to a ganglion, and later cut those 

 running from it, and observe if the second section increases the para- 

 lytic effects of the first section. 



2. We may compare the extent of the paralysis produced, when in 

 one animal the nerve fibres running to a ganglion are cut, and in another 

 animal the nerves running from the ganglion. 



3. We may compare the extent of the paralysis when the nerve 

 fibres are cut, as in (2), but on the right and left side of an animal 

 instead of in different animals. 



Before dealing with the experiments which have been made on these lines, 

 we may note that the peripheral ganglia of adult animals do not, so far as 

 we know, depend for their nutrition on receiving impulses from the central 

 nervous system. In some cases, in the central nervous system, removal of the 

 normal impulses to the nerve cells causes them to atrophy. The nerve cells of 

 the peripheral ganglia remain functionally active for a very long time after 

 severance of their pre-ganglionic fibres. It was noticed by Budge 1 that a year 

 after section of the cervical sympathetic, stimulation of the superior cervical 

 ganglion still caused dilatation of the pupil, although the nerve itself had not 

 regenerated. Further, so far as the reagents in use show, the nerve cells retain 

 their normal appearance. 



1. It may be doubted whether the first form of experiment mentioned above 

 is one which will give convincing results, unless there is a considerable in- 

 terval of time between the two operations, for it cannot be said with certainty 

 how long it takes for the stimulating effect of the first section to disappear 

 completely. So far, at any rate, the method has not yielded anything decisive 

 on the question. 



Some interesting observations have been made on the effects of removal in 

 the frog 2 of the sympathetic ganglion which sends fibres to the pupil. They 

 do not, however, allow any well-founded conclusion to be drawn as regards 

 the automatism of the nerve cells. 



Dastre and Morat 3 state that, in the dog, section of the cervical sympathetic 

 does not cause flushing of the bucco-facial region, whilst excision of the 

 superior cervical ganglion does. I have not been able to find any such con- 

 stant difference in the effect of the two operations. 



Dastre and Morat found a greater dilatation of the vessels of the ear (and 



1 Budge, "Ueber die Bewegung d. Iris," Braunschweig, 1855, S. 125. Budge, how- 

 ever, attributed the effect to pupillo-dilator fibres running to or through the ganglion from 

 the hypoglossal. 



2 Liegeois, Compt. rend. Soc. de biol., Paris, 1862, p. 71 ; Vulpian, "Leeons sur 

 Fappareil vaso-moteur, " p. 312 ; cf. also Budge, Arch. f. physiol. Heilk., Stuttgart, 1852, 

 S. 773 ; Tuwim, Arch. f. d. ges. Physiol., Bonn, 1881, Bd. xxiv. S. 115. 



3 "Systeme nerveux vaso-moteur," Paris, 1884; Arch, de physiol. norm, et path., 

 Paris, 1892, p. 171. 



