468 



SYMPATHETIC NERVE. 



well as from surgical operations, would seem 

 to show that such is the case. The coats of 

 the blood-vessels he considers to be destitute 

 of sensibility, inasmuch as he found that the 

 operation of fixing the haema-dynamometer 

 into them gave rise to no distinct sign of 

 pain. 2nd. As regards the fibres which take 

 their origin from the ganglia, it seems in a high 

 degree probable that they at least cannot 

 convey impressions from the organs which 

 they supply to the sensorium. In order to 

 communicate such impressions they must 

 transfer them to fibres which do not terminate 

 in the ganglia, but are directly or indirectly 

 connected with the sensorium, and are, in 

 short, true sensory fibres. Such a trans- 

 ference in the normal condition does not, 

 ho waver, appear to take place. 3rd. It is 

 not at all probable that fibres, which in ani- 

 mals that have been beheaded, or are under 

 the influence of strychnine, show so little 

 connection with the spinal cord that stimulus 

 applied to them cannot excite any reflex 

 movements in the voluntary muscles, should 

 be in a condition to communicate impressions 

 through the spinal cord to the sensorium. 

 4th. Division of the cerebro-spinal nerves 

 which supply the integument is followed by 

 loss of sensibility in that part, although the 

 sympathetic fibres passing to the same have 

 been left uninjured. In the frog, a great 

 number of fibres are sent from the sympathetic 

 to the cerebro-spinal nerves, and are along with 

 these distributed in considerable quantity to the 

 integument : if now the nerves in the leg of the 

 frog be divided above the point at which the 

 fibres of the sympathetic join them, so as in this 

 way to leave the continuity of the latter unin- 

 jured, the limb is notwithstanding deprived of 

 sensibility ; the power of exciting reflex action 

 in the muscles of the limb by stimulus applied 

 to the integument being also at the same time 

 destroyed. Division of the fifth nerve, in 

 like manner, is attended by loss of sensibility 

 in all the parts of the face supplied by this 

 nerve ; and no reflex action can be excited by 

 stimulus applied to the eye, tongue, &c., al- 

 though these parts derive fibres from the 

 sympathetic, which are not divided in the 

 operation. Although in the normal condition 

 the fibres in question are not capable of com- 

 municating impressions to the sensorium, they 

 may, however, according to Volkmann, do so 

 in diseased states. In this way the severe 

 pain which is sometimes felt in organs sup- 

 plied by the sympathetic, does not depend so 

 much on cerebro-spinal nerve-fibres as on 

 an altered condition of the ganglionic fibres 

 themselves. The number of cerebro-spinal 

 fibres distributed to such parts is too small to 

 explain it. Severe pain is frequently felt in 

 bones when diseased, although, according to 

 Volkmann, these probably receive none but 

 sympathetic filaments. The circumstance 

 already mentioned, that in experimenting on 

 the sensibility of the ganglia, it has been found 

 that these are frequently incapable of trans- 

 mitting impressions until by frequent irrita- 

 tion they have been brought into a kind of 



inflammatory condition, also indicates the 

 same thing. 



All the fibres which are sent from the 

 cerebro-spinal system to the sympathetic, 

 through the medium of the communicating 

 branches, are probably derived, according to 

 Volkmann, from the posterior roots of the 

 spinal nerves alone, and are not therefore 

 possessed of motor properties. They hold 

 the relation of centripetal or afferent fibres 

 to the ganglia of the sympathetic. The motor 

 properties of the sympathetic are therefore 

 considered by him to be due entirely to the 

 fibres which arise in the different ganglia. In 

 regard to those movements which, as already 

 stated, are excited in organs supplied with 

 sympathetic nerves, by irritation of the cen- 

 tral masses of the nervous system, Volkmann 

 holds that the stimuli to contraction in these 

 cases are not transmitted directly to the 

 organs in which the contractions are mani- 

 fested, but are first conveyed by the fibres in 

 the rami communicantes to the ganglia of 

 the sympathetic, where transference to the 

 proper sympathetic fibres takes place. 



Thus, then, according to Volkmann, the 

 motor properties of the sympathetic are en- 

 tirely due to the proper ganglionic fibres. 

 The painful sensations which are sometimes 

 felt in parts supplied by the sympathetic are 

 due, not so much to fibres of cerebro-spinal 

 origin as to an altered condition of the gan- 

 glionic fibres, while the fibres which are sent 

 to the sympathetic by the cerebro-spinal sys- 

 tem act as afferent or centripetal fibres to 

 the different ganglionic centres, and by means 

 of which a connection is established between 

 the sympathetic and cerebro-spinal systems. 



According to Valentin, again, both the 

 motor and sensory properties of the sym- 

 pathetic are due entirely to cerebro-spinal 

 fibres. 



It is generally admitted that the sympa- 

 thetic receives fibres from the anterior as well 

 as from the posterior roots of the cerebro- 

 spinal nerves. The number of these fibres 

 must, moreover, be very considerable, espe- 

 cially in the higher animals ; it would seem 

 probable, therefore, that the motor, and 

 especially the sensory properties of the sym- 

 pathetic are in part due to these fibres. The 

 experiments of Budge and Waller show, al- 

 most beyond a doubt, that, in the case of the 

 iris at least, the motor fibres which pass to 

 it through the medium of the sympathetic are 

 derived from the spinal cord. The circum- 

 stance, however, that the organs supplied by 

 the sympathetic cannot be influenced by the 

 will, and in the normal condition are removed 

 beyond the sphere of sensation, would seem 

 to indicate that the conducting power of 

 these fibres must be modified by the different 

 ganglia through which they pass in some such 

 way as Volkmann supposes. 



Are the ganglia to be regarded as centres 

 of reflex action? By Valentin*, Longetf, 

 and others, they are denied this property. 



* Op. cit. p. 697., as quoted by Longet. 

 t Op. cit. p. 578. 



