SYMPATHETIC NERVE. 



view that its movements depend upon these 

 parts is chiefly founded, are explained by 

 Volkmann as taking place by reflex action 

 through the medium of the sympathetic gan- 

 glia. The fibres which pass from the spinal 

 cord to the ganglia stand to the proper sym- 

 pathetic fibres arising in these in the same 

 relation in which the ordinary sensory fibres 

 stand to the motor fibres of the muscles of 

 animal life. 



A conclusive way of determining whether 

 the movements of the heart, as well as the 

 order in which.these take place, depend, or not, 

 upon the ganglia contained in its substance, 

 would be to ascertain whether they still con- 

 tinue after the ganglia have been extirpated. 

 These, however, are so small, and apparently 

 so numerous, as to render such an experiment 

 impossible. That the continuance of these 

 movements after the brain and spinal cord is 

 destroyed, as well as when the heart is re- 

 moved from the body, cannot be attributed to 

 mere irritability of the muscular fibres acted on 

 by the stimulus of the blood or of the atmo- 

 spheric air, but must be connected with 

 nervous influence, is rendered probable by 

 several circumstances, but especially by the 

 observation first made by Henry, and after- 

 wards by Miiller*, that solution of opium or of 

 other narcotic substances, when applied to the 

 outer surface of the heart, does not produce 

 any obvious alteration in its action, whereas 

 when introduced into its cavities so as to be 

 brought into contact with its inner surface, 

 their almost immediate effect is to cause this 

 to cease. Again, when stimulus is applied to 

 one of the ventricles of a heart which has 

 just ceased pulsating, the contraction thereby 

 produced does not commence at the point 

 irritated, as might be expected were the 

 irritability of the muscular fibres alone con- 

 cerned, but in the auricles, and is followed 

 by contraction of the ventricles. Sometimes, 

 indeed, stimulus applied to the ventricles is 

 followed by contraction of the auricles alone. 

 Even when the stimulus is applied to the 

 apex of the organ, the contraction still com- 

 mences in the auricles, and sometimes limits 

 itself to these. The regular order in which 

 ks movements take place, so different from 

 those produced in the ordinary muscles by 

 direct application of external stimuli, would 

 imply that the impulse by which they are 

 produced must be conveyed in a certain de- 

 finite direction to the different muscular parts 

 of which the heart is composed ; and this can 

 only be supposed to be effected through the 

 medium of its nerves. The mere arrangement 

 of the muscular fibres of the heart seems in- 

 sufficient to account either for the general 

 contraction of auricles and ventricles or for 

 the order in which these succeed one another. 

 If, in the case of the heart, the contraction of a 

 single bundle of the muscular fibres may act as 

 a stimulus to the neighbouring fibres, by which 

 they also are excited to contraction, the same 

 thing ought to take place in the muscles 

 of animal life : the bundles in these, though 

 * Mailer's Arcliiv. 1845, p. 423, et seq. 



presenting a different arrangement from those 

 in the heart, are, notwithstanding, in as close 

 contact with one another as are the latter, 

 and have equal facility for stimulating the 

 neighbouring bundles to contraction. The 

 dependence of the rhythmical movements of 

 the heart upon a certain arrangement of its 

 nerves, and moreover that there are certain 

 portions of the same from which the stimuli 

 to contraction proceed, is further indicated 

 by the effects, as shown by Volkmann, which 

 follow incisions made into the heart's sub- 

 stance. When a transverse incision is made 

 ' through the heart, between its auricles and 

 ventricles, the former have been found to 

 continue their contractions much longer than 

 the latter ; and if a longitudinal incision be 

 made gradually proceeding from apex to base, 

 the rhythm is preserved in both portions until 

 the heart has been divided half way; when 

 the incision is continued further, however, the 

 movements of either part become irregular. 

 When the ventricle is divided transversely into 

 two portions, that towards the apex either 

 ceases its contractions immediately or con- 

 tinues the same only for a short time, whereas 

 that which is still in connection with the 

 auricles goes on contracting as before. 



It has also been observed that in the heart 

 of the frog there is one portion of the septum 

 between the auricles which continues its con- 

 tractions much longer than any other part ; 

 and in this portion the greatest number of the 

 cardiac ganglia and nerves are situated. It 

 was also observed by Kolliker that the trans- 

 verse groove in the frog's heart in like manner 

 exercised a marked influence on its rhythmical 

 contractions ; and here also the ganglionic 

 corpuscles and nerves are very abundant. In 

 young kittens and rabbits also, Valentin has 

 likewise observed that the groove in question 

 affects the movements of the heart very much. 



The opinion of Volkmann, therefore, that 

 the rhythmic contractions of the heart are 

 connected with a nervous centre, and more- 

 over that this nervous centre is the sympa- 

 thetic ganglia contained in the heart's sub- 

 stance, seems highly probable. At the same 

 time there cannot be the least doubt that an 

 influence may be exercised over these move- 

 ments by the central masses of the nervous 

 system. 



Intestinal canal. (Esophagus. The ceso- 

 phagus receives nerve-fibres both from the 

 pneumogastric and sympathetic. The former 

 is, according to Longet *, the source of its 

 sensibility as well as of its motion, while the 

 sympathetic presides over the secretion of the 

 mucus with which its inner surface is lubri- 

 cated. Valentin, however, as mentioned by 

 Longet, found, on irritating the cervical por- 

 tion of the main cord of the sympathetic 

 in the rabbit, that movements were pro- 

 duced in the middle portion of the ceso- 

 phagus ; and contractions were also produced 

 in the thoracic portion of the same tube 

 when the inferior cervical ganglion or either 

 of the first four thoracic ganglia was irritated. 



* Op. cit. p. G07. 



