MEDULLA OBLONG ATA. 407 



Halle, and Percy. 1 Flourens, in his elaborate experiments 

 upon the nerve-centres, extended the observations of Legal- 

 lois, and limited the respiratory centre in the rabbit, between 

 the upper border of the roots of the pneumogastrics and a 

 plane situated about a quarter of an inch below the lowest 

 point of origin of these nerves ; these limits, of course, vary- 

 ing with the size of the animal. 3 Following these experi- 

 ments, Longet has shown that the respiratory nervous centre 

 does not occupy the whole of the medulla included between 

 the two planes indicated by Flourens, but that it is confined 

 to the gray matter of the lateral tracts, or the intermediary 

 fasciculi. This was demonstrated by the fact that respiration 

 persists in animals after division of the anterior pyramids 

 and the restiform bodies. Subsequently, Flourens still far- 

 ther restricted the limits of the respiratory centre, and fully 

 confirmed the observations of Longet. 3 



The portion of the medulla oblongata above indicated 

 presides over the movements of respiration, and is the true 

 respiratory nerve-centre. Kearly all who have repeated the 

 experiments of Flourens have found that the spinal cord 

 may be divided below the medulla oblongata, and that all 

 of the encephalic ganglia above may be removed, respiratory 

 movements still persisting. It is a very common thing in 

 vivisections to kill an animal by breaking up the medulla. 

 In a dog, for example, we grasp the head firmly with the 

 left hand, flex it forcibly on the neck, and penetrate with a 

 stylet a little behind the occipital protuberance, entering be- 

 tween the atlas and the skull. By a rapid lateral motion of 

 the instrument, the medulla is broken up, and the animal in- 

 stantly ceases to breathe. There are no struggles, no mani- 

 festations of the distress of asphyxia ; the respiratory mus- 



1 LEGALLOIS, op. cit., tome i., p. 248. 



2 FLOUREXS, Systeme nerveux, Paris, 1842, p. 204. 



Flourens was in error when he stated (page 197) that Lorry was the first to 

 show that animals were instantly killed by destruction of the summit of the 

 ppinal cord, for this was distinctly indicated by Galen, in the second century. 



3 LONGET, Traite de physiologic, Paris, 1869, tome iii., pp. 387, 388. 



