SYMPATHETIC NERVE. 



459 



that clear indications of pain were elicited. 

 From ligature applied to the renal nerves, as 

 well as from the application of chemical or 

 mechanical stimuli to the semilunar ganglia, 

 animals suffered great pain. So, also, 

 Flourens* found that on irritating ,the semi- 

 lunar ganglion in dogs the animals exhibited 

 distinct signs of pain, and the same results were 

 obtained by Brachet f , from irritation of the 

 thoracic ganglia. Frequently, according to 

 Brachet, stimuli, when first applied to a part 

 of the nerve, do not give rise to pain ; after- 

 wards, however, when the part has been ex- 

 posed to the air for some minutes, if irritation 

 be now applied distinct signs of pain are 

 elicited. Longet J, in like manner, found that 

 on irritation of the semilunar ganglia the 

 animal almost invariably exhibited indications 

 of more or less pain being produced. In other 

 animals, where the lumbar ganglia were sub- 

 jected to experiment, he found, like Brachet, 

 that it was only after prolonged irritation that 

 signs of pain were evinced. So, also, accord- 

 ing to Valentin $, when the cavities of the 

 thorax or abdomen are opened as quickly as 

 possible, and pressure applied to the semi- 

 lunar ganglion, to the splanchnics, or to any 

 other branch of the sympathetic, sometimes 

 no signs indicative of sensibility are evinced. 

 When, however, they have been exposed to the 

 air for a short time they generally exhibit these 

 properties in greater or less degree. The 

 severe pain which frequently attends diseases 

 of parts supplied exclusively by the sympa- 

 thetic nerve, also affords still better evidence 

 than can be derived from experiments of the 

 existence of sensory nerve fibres in the sym- 

 pathetic. 



Different parts of the nerve appear to 

 exhibit the property of sensibility in different 

 degrees. In regard to this point, Valentin jj 

 gives the following as the results of his ex- 

 periments. 1st. The very grey branches which 

 have passed through several ganglia do not, 

 when the stimulus applied to them is slight, 

 give rise to any signs which would indicate 

 that pain was produced. Such branches are 

 those which pass along the mesentery to the 

 intestine ; strong stimuli, however, such as 

 the application of a ligature or of chemical 

 irritants, cause, when applied even to these 

 branches, distinct signs of pain. 2nd. Irritation 

 of the ganglia themselves is followed by signs 

 of pain either immediately or after a short 

 time. 3rd. The connecting cord of the sym- 

 pathetic is similarly circumstanced in regard 

 to sensibility as the ganglia. 4th. The rami 

 communicantes are as highly endowed with 

 sensibility as the posterior roots of the neigh- 

 bouring spinal nerves. He found that section 



* Rech. Experimental, sur les propr. et les Fonc- 

 tions du System. Xerv. p. 229., as quoted by Longet. 



t Rech. Experiment, sur les Fonct. du Systeme 

 Xerv. Gangl. 2nd edit, Paris, 1837, p. 3o7., as 

 quoted by Longet. 



t Op. "cit. ii. p. 566. 



Lehrbtich der Physiologic des Menschen, 1844, 

 band ii. p. 421. 



|| Op. cit. band ii. p. 422., as quoted by Longet. 



of a communicating branch did not destroy 

 the sensibility of the corresponding ganglion : 

 the main cord of the sympathetic must also be 

 divided above and below the ganglion before 

 this ensues. In the lumbar region Brachet* 

 found that, when the communicating branches 

 of three successive ganglia were divided, the 

 central ganglion was deprived of its sensory 

 properties. The greater the number of ganglia 

 intervening between the point of the branches 

 of the sympathetic, to which the irritant is 

 applied, and the cerebro-spinal centres, the 

 less distinctly, according to Valentin, does it 

 give rise to signs of pain. Hence, the peri- 

 pheral branches are the least sensitive, while 

 the rami communicantes are the most highly 

 endowed with this property, the connecting 

 or main cord of the sympathetic and ganglia 

 being intermediate in this respect between 

 these two. The nature of the stimulus ap- 

 plied has also an influence on the results 

 produced : when the ganglia are merely pricked, 

 or their branches quickly divided, sometimes 

 no sign of sensibility is evinced, whereas 

 pressure, application of nitric acid or potash 

 to the same parts give rise to distinct expres- 

 sions of pain. 



In regard to the experiments which are 

 made with a view to ascertain the sensory 

 properties of this nerve, it is to be observed 

 that in general it is only by application of 

 very powerful stimuli that the phenomena of 

 sensibility are elicited : they seem to act by 

 producing a more or less abnormal condition in 

 the part of the nerve to which they are ap- 

 plied, and hence the effects they produce may 

 be regarded as belonging to the same category 

 as the phenomena observed in diseased con- 

 ditions of the organs supplied by this nerve. 

 In the normal or healthy condition the fibres 

 of the sympathetic seem to be almost entirely 

 destitute of the property of communicating 

 impressions to the sensorium. We do not 

 know, as Volkmann observes, whether the 

 organic muscles be at rest or in motion ; 

 whether the glands secrete in larger or in 

 smaller quantity ; whether the gall-bladder be 

 full or empty. We are sensible of the impres- 

 sions made by the particles of food so long as 

 they remain in the mouth, but, as soon as they 

 reach the stomach or intestinal canal, we are 

 no longer aware of their presence. 



Motor properties. That the sympathetic 

 contains motor nerve fibres there can be no 

 doubt ; irritation of its branches being followed 

 by movements in the different muscular organs 

 to which they are distributed. Thus irrita- 

 tion of the splanchnic nerves in the living 

 animal, or immediately after death, is generally 

 followed by more or less extensive contrac- 

 tions in the small intestine. Miiller observed 

 that the same result followed irritation of the 

 semilunar ganglion : the same observation has 

 also been made by Kiirschner.f Mechanical 

 or chemical irritation, but especially galvanic 



* Op. cit. p. 360., as quoted by Longet. 



f Abhandlungen ttber das Xerven System, von 

 M. Hall. Aus dem Englischen von D. C. KUrsh- 

 ner, Marburg, 1840, Xachtraege, p. 182. 



