408 NEKVOUS SYSTEM. 



cles simply cease their action, and the animal loses instantly 

 the sense of want of air. A striking contrast to this is pre- 

 sented when the trachea is tied or when all of the respiratory 

 muscles are paralyzed without touching the medulla. The 

 same phenomena follow injury to the medulla in the human 

 subject ; and in anaesthesia from the administration of chlo- 

 roform, a patient w r ill sometimes suddenly stop breathing, 

 apparently because the medulla oblongata becomes affected. 



In another volume, we have insisted upon the mechan- 

 ism of the reflex phenomena of respiration. AYe have con- 

 clusively shown by experiments, that an impression is re- 

 ceived by the sensory nerves of the general system, due to 

 want of oxygen, and not to the irritation produced by carbon- 

 ic acid ; and that this impression is conveyed to the medulla 

 oblongata, and gives rise to the reflex movements of respira- 

 tion. If this impression be abolished, there are no respira- 

 tory movements ; and if the medulla, the sole centre capable 

 of receiving this impression and of generating the stimulus 

 sent to the respiratory muscles, be destroyed, respiration in- 

 stantly ceases, without any sensation of asphyxia. 1 



It does not seem that there can be any doubt with regard 

 to the action of the medulla oblongata as the respiratory 

 nervous centre ; still, it has been stated by Brown-Sequard, 

 that the commonly-accepted view is not correct ; that the 

 sudden arrest of respiratory movements following destruc- 

 tion of the medulla is due to irritation and not to its re- 

 moval ; and that, in certain cases, the movements may become 

 reestablished after the irritation has subsided. 2 Schiff noted, 

 in 1852, that dogs lived for a certain time after injury of 



1 See vol. i., Respiration, p. 479, et seq. 



Our original experiments on the respiratory sense were made in 1860-'61, 

 and published in October, 1861. See Experimental Researches on Points con- 

 nected with the Action of the Heart and with Respiration. American Journal of 

 the Medical Sciences, Philadelphia, October, 1861. 



2 BROWX-SEQUARD, Recherches snr les causes de mort apres V ablation de la 

 partie de la moelle allongee qui a ete nommee point vital. Journal de la physiolo- 

 gie^ Paris, 1858, tome i., p. 217, et seq. ; and, Recherches experimentales sur la 

 physiologie de la moelle allongee. Ibid., 1860, tome iii., p. 151, et seq. 



