456 



SYMPATHETIC NERVE. 



by the sympathetic in the circumstance that 

 the normal impressions which are made upon 

 them do not reach the sensorium. Thus, the 

 greater part of the mucous membrane which 

 lines the bronchial tubes, as well as that of 

 the oesophagus, receives its nerves from the 

 eighth pair; the lacrymal glands receive fila- 

 ments from the fifth nerve ; and from the fifth 

 and seventh nerves fibres are distributed to 

 the salivary glands : and yet all these organs 

 present the same relations in regard to sensi- 

 bility as the pancreas or other glands which 

 derive their nerves from the sympathetic. 

 The fact of certain parts being beyond the 

 control of the will, and from which the or- 

 dinary impressions they receive are not con- 

 veyed to the sensorium, does not so much 

 depend on any peculiarity in the nerves with 

 which they are supplied, as upon their ana- 

 tomical constitution. Such is the case, for 

 example, with the muscular fibres presenting 

 the same characters as those which are found 

 in the walls of the ducts of the various glands, 

 as well as with those which are present in the 

 coats of the blood and lymphatic vessels. That 

 the impossibility of influencing these structures 

 by any effort of volition, as well as the fact of 

 their being removed from the sphere of sen- 

 sation, do not depend on any peculiarity in 

 the propei ties of their nerves, is shown, Valen- 

 tin says, by the fact that the greater part of 

 the nerves for the salivary glands are derived, 

 as above stated, from the fifth and seventh 

 cerebral nerves. The same thing also holds 

 true, according to him, of the mammary 

 glands, the nerves supplied to which proceed 

 chiefly from the supra-clavicular and inter- 

 costal nerves. As regards the argument which 

 is drawn in favour of the views of Bichat, 

 from anencephalous foetuses, Valentin re- 

 marks that there is no evidence to show that 

 in the development of the various organs in 

 the foetus nervous influence is at all concerned ; 

 and, moreover, that the phenomena of growth 

 and nutrition are not dependent on the sym- 

 pathetic is shown by the circumstance of few 

 or no sympathetic fibres being sent to the extre- 

 mities. The sympathetic is moreover capable 

 of transmitting stimuli to and from the cerebro- 

 spinal centres, in the same manner as the ordi- 

 nary nerves arising from these, though in a less 

 degree; stimulus applied to the spinal cord being 

 capable of exciting contractions in the heart 

 and intestinal canal, while on the other hand 

 stimuli applied to the latter may also be trans- 

 mitted to the former. This is shown by the 

 severe pain which is felt in organs supplied by 

 the sympathetic, when affected with disease, 

 as well as by the circumstance that irritations 

 of the intestinal canal not unfrequently give 

 rise to contractions in the muscles of animal 

 life : as is not unfrequently the case with 

 children, when the presence of worms in the 

 intestinal canal gives rise to impressions 

 which are conve\ed along the centripetal 

 nerves to the spinal cord, and are there trans- 

 ferred to the motor nerves which pass to the 

 voluntary muscles, exciting them to contrac- 

 tions. As already stated, Valentin believes 



that all the true nerve-fibres which are pre- 

 sent in the sympathetic, are derived from the 

 brain and spinal cord ; on entering the sym- 

 pathetic they pass through a greater or 

 smaller number of its ganglia, and are then 

 distributed to the different organs, in the same 

 way as the ordinary cerebro-spinal nerves. 

 The sympathetic is therefore, according to him, 

 a cerebro-spinal nerve, possessed of the same 

 properties, and deriving these from the same 

 source as the other cerebro-spinal nerves ; the 

 only peculiarities in the sympathetic being its 

 numerous points of origin, as well as the 

 large number of ganglia which it presents. 

 Similar views are also held by Longet*, and 

 others. 



After the discovery of the gelatinous fibres 

 in the sympathetic, it was held by some, that 

 while motion and sensibility in the organs sup- 

 plied by this nerve depended upon the tubu- 

 lar nerve fibres sent to them through the 

 medium of tlie branches of the sympathetic 

 by the brain and spinal cord, the processes of 

 nutrition depend upon the gelatinous or pro- 

 per sympathetic fibres. Moreover, as these 

 fibres are found in the cerebro-spinal nerves 

 also, it is supposed that they pass to the ex- 

 tremities along with the cerebro-spinal nerves, 

 where they in like manner preside over the 

 nutrition of these parts. According to these 

 authors, the ganglia are so many centres, from 

 which nerve fibres, possessing peculiar pro- 

 perties, pass off in different directions ; some 

 to the viscera, others to the extremities, along 

 with the cerebro spinal nerves, and by means 

 of which the nutritive processes are regulated. 

 Thus, while the internal viscera receive sen- 

 sory and motor nerve fibres from the brain 

 and spinal cord, they, as well as the organs of 

 animal life, receive the nerve fibres which 

 regulate the nutritive processes from the sym- 

 pathetic. Such seems to be the view of 

 Remak-f-, R. Hall if, and others. 



Volkmann$ adopts the same view as was 

 held by Bichat, regarding the sympathetic as 

 constituting a system of nerves distinct from 

 and independent of the cerebro-spinal system. 

 Under the term sympathetic, he includes not 

 only the sympathetic, commonly so called, 

 but also the ganglia which occur on the pos- 

 terior roots of the spinal nerves, as well as 

 those which are present on several of the 

 cerebral nerves. All the finer nerve fibres 

 are regarded by him as sympathetic fibres. 

 These originate in the different ganglia ; some 

 of them pass inwards to the viscera, over 

 whose movements and nutrition they preside, 

 while others pass along with the cerebro- 

 spinal nerves to the extremities, and serve as 

 the nerves of nutrition to these parts. Each 

 of the ganglia he regards as a nervous centre. 



* Anatomie et Physiologic de Systems Nerveux, 

 tome ii. p. 569. et seq. 



t Observat. Anat. et Microscop. de Systemat. 

 Nerv. Structura, Merlin, 1838. 



J Edinburgh Medical and Surgical Journal, July, 

 1840, &c. 



Wagner's Handworterbuch der Physiologie 

 Zehnte Lieferung, p. 499. 



