SYMPATHETIC NERVE. 



461 



question contains fibres derived both from 

 the sympathetic and also from the pneumo- 

 gastric. Again, such a restraining power must 

 hold an opposite relation to the moving power 

 in the normal condition ; the moving power 

 would therefore express itself only in part, 

 according as the other is in a latent state or 

 in a state of activity, and consequently sec- 

 tion of the vagus nerve ought, did it exert 

 the restraining power in question, to be fol- 

 lowed by an acceleration in the movements 

 of the organ, which is not the case. Budge, 

 therefore, seems to regard the fibres which 

 are sent to the heart in the frog by the pneu- 

 mogastric, as possessed of motor and sensory 

 properties. 



Schift* also found that when the heart's 

 action has been made to cease by application 

 of the wires to the groove between the au- 

 ricles and ventricles, this effect cannot be 

 counteracted by applying them to the bulbus 

 arteriosus. The phenomenon of the cessa- 

 tion of the heart's action, produced by the 

 application of the galvanic stimulus to the 

 pneumogastric, he explains by supposing 

 that its fibres are in a state of activity 

 during the systole of the corresponding 

 part of the heart, but quickly become ex- 

 hausted, thus allowing the diastole to take 

 place: thereafter, their activity being again 

 renewed, a second systole results. When 

 therefore, strong galvanic stimuli are applied 

 to the nerve the state of exhaustion continues 

 longer and in the same proportion the dia- 

 stole, or cessation of the heart's action, is also 

 longer. 



In accordance with the above views, Valen- 

 tin * in like manner holds that the sympa- 

 thetic has no influence over the movements 

 of the heart in the frog, neither giving rise to 

 acceleration nor stoppage of its action. 



In regard to the connection between the 

 central masses of the nervous system and the 

 action of the heart, it is evident, from what 

 has been above stated in regard to the effects 

 which are produced by the application of the 

 galvanic stimulus to the pneumogastric nerve, 

 that a certain influence must be exercised by 

 these. By Willis f, and others, it was held 

 that the movements of the heart, as well as 

 of the other inorganic muscles, depend upon 

 the cerebellum. "This they believed from the 

 circumstance that the nerves which preside 

 over the involuntary actions were supposed 

 to take their origin from this part of the ner- 

 vous system, and also from observing that 

 wounds upon the back part of the head proved 

 speedilv fatal. HallerJ, again, endeavoured 

 to show that the action of the heart is en- 

 tirely independent of nervous influence, and is 

 due merely to the inherent irritability of the 

 muscular fibres. From the circumstance that 

 sudden destruction of the spinal cord im- 

 mediately produces an interruption of the 

 heart's action, Legallois concluded that its 



* Loc. cit. p. 694. 



f Cerebr. Anatomia Xervorumque Descript. et 

 Usus, p. 195. 



J Dissertat. sur 1'Irritabilite, t. i. p. 72. 



movements are not due to inherent irritability, 

 as Haller maintained, but depend upon the 

 spinal cord. The cessation produced in the 

 way just stated, although indicating that an 

 influence may be exercised through the cen- 

 tral nervous masses upon the movements of 

 the heart, by no means implies the conclusion 

 which was drawn from it by Legallois, in- 

 asmuch as the heart may sometimes in such 

 cases again begin to pulsate. That the heart 

 may be influenced in its action through the 

 medium of the central masses of the nervous 

 system is also shown by the effects which are 

 produced by the application of the galvanic 

 stimulus to these parts. Thus, in the frog, 

 as shown by the experiments of Weber*, 

 Budge-j-, Valentin , and others, it may be 

 made to cease pulsating by applying the wires 

 of the magneto-electric rotation apparatus to 

 either side of the medulla oblongata. Unless 

 there has been much loss of blood in exposing 

 the parts the heart becomes dark-red, and is 

 very much distended; where the large blood- 

 vessels have been previously cut the heart 

 still ceases to pulsate when the stimulus is 

 applied as above : it does not, however, pre- 

 sent the dark-red distended appearance, but 

 is more or less collapsed and pale. The ex- 

 periment, according to them, seldom or never 

 fails. If the electric stimulus has been ap- 

 plied for too long a time the heart again begins 

 to beat, in the same way as takes place when 

 the stimulus is applied to the trunk of the 

 pneumogastric nerve. The same stimulus also 

 sometimes produces more or less change in 

 the rhythm of the organ. According to the 

 Webers, the portion of the central nervous 

 masses which, when stimulated in this man- 

 ner, gives rise to a cessation in the action of 

 the heart, is that extending from the corpora 

 quadrigemina to the posterior extremity of 

 the calamus scriptorius. Budge found, in his 

 experiments, that the corpora quadrigemina 

 were not so intimately concerned in the pro- 

 duction of these effects as the medulla ob- 

 longata. Tiedemann appears to regard the 

 cerebellum and the medulla oblongata as the 

 parts through which the cessation of the 

 heart's action may be induced, while stimulus 

 applied to the corpora quadrigemina produces 

 no effect. Valentin believes that while the 

 corpora quadrigemina and cerebellum exercise 

 a certain influence, the medulla oblongata is 

 the part chiefly concerned. In nine mice, 

 which were rendered insensible by chloroform, 

 and whose hearts and medulla oblongata were 

 laid bare, Valentin endeavoured to ascertain 

 the parts of the central nervous masses which, 

 when stimulated in the way above mentioned, 

 give rise to cessation of the heart's action, as 

 also the effects which are produced by the 

 same stimulus when applied to the spinal 

 cord. In none of them did he observe any 



* "Weber, "Wagner's Handwbrterbuch, band iii., 

 2nd Abtheil, p. 44. 



f Ibid. p. 415. &c. 



j Lehrbuch der Physiologic, band ii. p. 464., 

 et seq. 



Midler's Archiv. 1847, p. 498. 



