SYMPATHETIC NERVE. 



469 



Prochaska* seems to have attributed such 

 properties to the ganglia, inasmuch as he ex- 

 plains the contraction of the heart by sup- 

 posing that the impressions which are made 

 upon the inner surface of the organ are trans- 

 mitted to the ganglia by means of sensory 

 nerves, and are there transferred to motor 

 nerve-fibres. Grainger -j-, in like manner, 

 holds that the ganglia are centres of reflex 

 action, and moreover that each ganglion pos- 

 sesses a distinct so-called excito-motory sys- 

 tem of nerves. From what has been already 

 stated, it will be observed that Volkmann 

 also holds the view that, in the ganglia, trans- 

 ference of impression from one fibre to another 

 takes place. From his earlier experiments!, 

 however, he was led to conclude that such 

 was not the case. He found, on applying 

 a stimulus to the surface of the intestines 

 in a newly-killed frog, that a contraction en- 

 sued which was not confined to the part 

 which had been stimulated, but extended for 

 a considerable distance on either side. After 

 destroying the spinal cord, and again applying 

 the stimulus, he now found that the contrac- 

 tion produced was merely local, confining itself 

 to the part irritated. The extended contrac- 

 tion first produced he believed to be clue to 

 reflex action, while the limited contraction in 

 the second experiment he regarded as a mere 

 stimulus movement. From the circumstance, 

 moreover.that the former took place while the 

 spinal cord yet remained, and the latter after 

 it was destroyed, he concluded that it was 

 thereby proved, 1st, that the spinal cord is 

 the centre in which the act of reflexion takes 

 place in the movements of the intestine ; and, 

 2nd, that the ganglia are destitute of such 

 power. Longetj) also states that it is only 

 while the spinal cord remains that contrac- 

 tions extending over large portions of the 

 intestine can be excited by local application 

 of stimuli, the contraction so produced limit- 

 ing itself, after the spinal cord is destroyed, to 

 the point irritated. As was shown by Henle, 

 however, there can be no doubt that move- 

 ments may be excited by application of 

 stimulus to the surface of the intestine after 

 the spinal cord is destroyed, which are as 

 extended as those excited in the same way 

 while it remains. The contractions produced 

 by local stimuli are so similar both before 

 and after the removal of the spinal cord as to 

 leave no doubt that it can have no share 

 therein. The only question is, whether the 

 difference in character between the extended 

 contractions and those which are limited to 

 the point irritated are due to reflex action, or 

 not. By Valentin and others, the extended 

 contraction is explained in the same way as 

 they endeavour to explain that of the heart, 

 by supposing a particular arrangement of the 

 muscular fibres, by means of which the con- 

 traction of one bundle acts as a stimulus to 



* Opera Minora, t. ii. p. 1G9., as quoted by Longet. 

 ( Observations on the Structure and Functions of 

 the Spinal Cord. 



J Miiller's Arcbiv. 1838, Einl. Theil. p. 15., &c. 

 Op. cit. p. 577. 



the neighbouring bundles, exciting them suc- 

 cessively to contraction. How far this is the 

 case it is difficult to determine ; it seems, 

 however, that the relation of the one bundle 

 of muscular fibres to the neighbouring bundles 

 in the intestine is not so different from what 

 it is in the ordinary muscles as to explain the 

 limited contractions which take place in the 

 latter, and the extended contraction of the 

 former, upon the application of local stimuli. 

 The opinion of Hcnle*, that they are of a 

 reflex nature, the centres of reflexion being 

 the grey matter of the sympathetic ganglia, 

 seems, therefore, to be the more probable. 

 Kiirschner also adopts the view that the gan- 

 glia are to be regarded as centres of reflex 

 action. On repeating Miiller's experiment of 

 irritating the solar ganglion with potash, he 

 observed that the movements thereby pro- 

 duced in the intestines did not commence at 

 a single point, but in several different coils of 

 the intestine at one and the same time. This 

 may, he says, be explained in either of two 

 ways : the stimulus had either affected di- 

 rectly all the motor filaments, by which these 

 different parts of the intestine are supplied, or 

 only a few of them ; and from these few a 

 transference took place, in the ganglion, to 

 the others. The latter he believes to be the 

 true explanation ; for he found it is quite the 

 same, as regards the extent of the movements, 

 whether the irritant is strongly or slightly 

 applied, and whether a finely-pointed rod of 

 potash or a broad surface of the same is em- 

 ployed. 



The contractions which are excited in the 

 heart by application of local stimuli would 

 seem to indicate more clearly that the ganglia 

 are reflex centres. When a heart has just 

 ceased pulsating application of a stimulus 

 gives rise to a contraction affecting the entire 

 organ, the contraction, too, taking place in 

 the same rhythmical manner in which it 

 takes place during life. After some time, the 

 stimulus, when again applied, gives rise to a 

 contraction which does not affect the entire 

 organ, but only the particular auricle or ven- 

 tricle to which it is applied, and after some 

 time farther the same stimulus gives rise 

 merely to local contractions. The former 

 two seem to be, as Volkmann regards them, 

 movements of reflex action, while the last is 

 a mere stimulus movement. The circumstance 

 that stimulus applied to the ventricles in such 

 a heart gives rise to contractions which com- 

 mence in the auricles, and therefore at a point 

 distant from that to which the irritation has 

 been applied, seems explicable only on the 

 supposition that the impression thereby pro- 

 duced is conveyed to a nervous centre, and 

 here transferred to fibres proceeding to the 

 part in which the contraction commences. 



The follovsing experiment of Volkmann 

 would also appear to favour the view in ques- 

 tion. He destroyed the spinal cord in a 

 newly beheaded frog, and satisfied himself 



* Froriep's Xeue Xotizen, band xii. p. 247., as 

 quoted by Kiirsdmer. 



ii H 3 



