306 



THE MEDULLA OBLONGATA. 



Fig. 148. 



Posterior view of medulla oblongata. 



cerebri ; 10, superficial section of the trans- 

 verse fibres of the pons ; 11, deeper section 

 of the transverse fibres of the pons ; 12, oli- 

 vary body ; 13, right olivary body, brought 

 into view by removal of the corresponding 

 pyramid. 



Fig. 148 is a posterior view of the me- 

 dulla oblongata : p, p, posterior pyramids, 

 separated by a posterior fissure ; r, r, resti- 

 form bodies, composed of, <?, c, posterior col- 

 umns, and </, d, part of antero-lateral col- 

 umns of the cord ; <2, #, olivary columns, as 

 seen on the floor of the fourth ventricle, sep- 

 arated by s, the median fissure, and crossed 

 by some fibres of origin of, n, ft, the seventh 

 pair of nerves. 



FUNCTIONS OF THE MEDULLA OBLONGATA. 



Viewed as a superposed continuation of the spinal cord, the medulla 

 Functions of oblongata is the tract of communication between that organ 



the medulla : an( j the brain : the anterior pyramids and olivary tracts con- 

 it is a tract of . , .... J , 

 communica- vey motor influences, and the resmorm tracts and posterior 



tion - pyramids sensations. By experiments similar to those which 



have been performed upon the cord, these conclusions have been main- 

 tained. 



But, besides this function of conduction, the medulla oblongata dis- 

 charges a most important duty as a nervous centre ; on it depend respi- 

 ration and deglutition. The brain may be wholly removed above, and 

 the spinal cord below, as far as the origin of the phrenic nerve, without 

 death necessarily ensuing, but on wounding the medulla oblongata, the 

 muscular movements necessary for the introduction of air are necessarily 

 stopped. 



Moreover, the medulla oblongata exhibits the property of reflex action. 

 Its relations to So far as the function of respiration is concerned, its chief 

 respiration. centripetal nerve is the pneumogastric, but the power which 

 it possesses is participated in by many others, perhaps by reason of the 

 venous condition into which the blood is brought from want of proper 

 aeration. The violent respiratory movements by the sudden application 

 of cold to the skin, the shower-bath, or dashing cold water on the face, 

 are converted by it into respiratory muscular motions. From it also 

 arise the movements required in the act of deglutition. 



Under this view of the functions of the medulla oblongata, it is to be 

 regarded as an exclusively automatic instrument, which can continue its 



