REFLEX ACTIONS FROM AUTONOMIC GANGLIA. 68 1 



Other instances of the same kind of action occur in the body. We have 

 seen that in the cat no pilo-motor fibres run ordinarily to the sympathetic 

 chain below the third lumbar nerve, and that the pilo-motor fibres from the 

 twelfth thoracic to the third lumbar nerves run downwards. But if any part 

 of the lumbar sympathetic chain be stimulated, erection of hairs takes place 

 in the areas of the skin innervated by two, three, or four of the ganglia 

 above the point stimulated. 1 The action can be produced after destruction of 

 the spinal cord, or after section of the white rami, but is annulled by injection 

 of nicotin ; and nicotin applied locally to any 

 one ganglion annuls the effect in the area 

 supplied by that ganglion. As with the hypo- 

 gastric pseudo-reflexes, so here we may put on 

 one side the posterior root fibres as being con- 

 cerned with the action, since stimulation of 

 these has no pilo-motor effect. It cannot be 

 due to commissural fibres proceeding from 

 lower ganglia to higher ones, since degenerat- 

 ive section of the sympathetic below the third 

 lumbar white ramus abolishes the action below 

 the point of section, but degenerative section 

 between the ganglia does not abolish the effect 

 of stimulating the upper cut end. It can then 

 only be produced by descending motor fibres, 

 the mechanism being diagrammatically as 

 shown in B, Fig. 316. 



Similar pseudo-reflexes occur in the upper 

 thoracic region of the sympathetic chain. We 

 have seen that there are no descending pilo- 

 motor fibres in the sympathetic in the region 

 between the ganglion stellatum and (about) the sixth thoracic ganglion. But 

 on stimulating any part of this region, after section of the white rami, erection 

 of hairs is obtained in the areas supplied by the two to six ganglia below the 

 point stimulated, and the action is stopped by injection of nicotin. 



The pilo-motor pseudo-reflexes from the sympathetic chain, which we have 

 just described, differ, it will be noticed, from those obtained from the hypo- 

 gastric nerve, in being produced on the same side of the body as the stimulation, 

 instead of on the opposite side (cf. B, Fig. 315). They are further interesting, 

 as giving an indication of the number of ganglia to which a single nerve fibre 

 sends branches. Generally speaking, there are fewer in the lumbar region than 

 in the upper thoracic region of the sympathetic. Further experiments are 

 required before any very definite statement can be made with regard to this ; 

 but, so far as the experiments have gone, it appears that the fibres running to 

 the lumbar ganglia send branches to three ganglia as a rule ; and the fibres to 

 the thoracic ganglia generally send branches to four or five ganglia. 



According to Franois-Franck, 2 stimulation of the central end of one limb 

 of the annulus of Vieussens, after severance of the connections of the ganglion 

 stellatum with the spinal cord, causes dilatation of the pupil. He attributes this 

 to a stimulation of sensory fibres, causing a reflex action in the ganglion stellatum. 

 In the cat I have not found a dilatation of the pupil in these circum- 

 stances ; usually there was no effect, but occasionally the stimulation caused 

 retraction of the nictitating membrane, and a slight separation of the 

 eyelids. I take these effects to be produced by motor fibres, and to be 

 pseudo-reflex and not reflex effects. They can hardly be due to an excitation 

 of nerve cells in the ganglion stellatum, since the local application of nicotin to 



FIG. 317. Impulse set up in the 

 endings of a branch of the post- 

 ganglionic fibre (po.g), though it 

 may irradiate to the other end- 

 ings of the same fibre, cannot 

 pass back to the pre-ganglionic 

 fibre (pr.g), and so cannot pro- 

 duce a pseudo-reflex action of the 

 kind described in the text. 



1 Langley and Anderson, Journ. Physiol., Cambridge and London, op. cit. 



2 Arch, dephysiol. norm, et path., Paris, 1894. 



