4:02 NERVOUS SYSTEM. 



reported by Brown-Sequard, in' an elaborate memoir on the 

 physiology and pathology of the protuberance. 1 



Medulla Oblongata. 



The chief points of interest in the physiological anatomy 

 of the medulla oblongata relate to the direction of its fibres, 

 their connection with the gray matter embedded in its sub- 

 stance, and the course of the filaments of origin of certain of 

 the cranial nerves. Concerning the deep origin of the large 

 root of the fifth, the motor-oculi externus, facial, pneumogas- 

 tric, spinal accessory, and the sublingual, we shall have noth- 

 ing to say in this connection, as we have already treated of the 

 physiological anatomy of these nerves with sufficient minute- 

 ness ; and we have now to study the functions of the medulla 

 oblongata, and particularly its action as a nerve-centre. 



Physiological Anatomy of the Medulla Oblongata. The 

 medulla oblongata is the oblong, enlargement which connects 

 the spinal cord with the various encephalic ganglia. It is 

 about an inch and a quarter in length, and nearly an inch 

 broad, at its widest portion. It rests in the basilar groove 

 of the occipital bone, extending from the atlas to the lower 

 border of the tuber annulare, with its broad extremity 

 above. Like the cord, it has an anterior and a posterior 

 median fissure. 



Apparently continuous with the anterior columns of the 

 cord, are the two anterior pyramids, one on either side. 

 Yiewed superficially, the innermost fibres of these pyramids 

 are seen to decussate in the median line ; but if these 

 fibres be traced from the cord, it is found that they come 

 from the white substance of its lateral columns, and that none 

 of them are derived from the anterior columns. The fibres 

 of the external portion of the anterior pyramids come from 



1 BROWN-SEQUARD, Recherclies sur la physiologic et la pathologic de la protu- 

 berance annulaire. Journal de la physiologic, Paris, 1858, tome i., p. 755, etseq. ; 

 and, Ibid., 1859, tome ii., p. 130, et seq. 



