630 NERVOUS SYSTEM. 



fibres, taking their origin from all of the gray nodules of the medulla, pass 

 to the parts of the encephalon situated above. 



The uncrossed pyramidal tracts of the spinal cord (columns of Tiirck) 

 pass to the encephalon, by direct fibres situated at the outer border of the 

 anterior pyramids of the medulla. 



The crossed pyramidal tracts of the cord decussate in the lower portion 

 of the medulla and constitute the greatest part of the anterior pyramids. 



Fibres from the anterior fundamental fasciculi, the anterior radicular 

 zone and from the mixed lateral columns of the cord, probably pass to the 

 gray matter of the medulla. 



The direct cerebellar fasciculi of the cord are continuous with the funic- 

 uli graciles of the medulla. 



The columns of Burdach are continuous with the restiform bodies of 

 the medulla. 



The columns of Goll pass to the medulla and are lost in the fasciculi 

 graciles. 



As far as the fibres of origin of the cranial nerves are concerned, it may 

 be stated in general terms that a number of the motor roots arise from 

 the gray matter of the floor of the fourth ventricle, the roots of the sen- 

 sory nerves arising from gray matter in the posterior portions. 



USES OF THE MEDULLA OBLOXGATA. 



It is hardly necessary to discuss the action of the medulla oblongata as a 

 conductor of sensory impressions and of motor stimulus to and from the 

 brain. It is evident that there is conduction of this kind from the spinal 

 cord to the ganglia of the encephalon, and this must take place through the 

 medulla ; a fact which is inevitable, from its anatomical relations, and which 

 is demonstrated by its section in living animals. Nor is it necessary to 

 dwell upon the general properties of the medulla, in which it resembles the 

 spinal cord, at least as far as has been demonstrated by experiments upon 

 living animals or upon animals just killed. It is difficult to expose this part 

 in the higher classes of animals, but experiments show that it is sensitive 

 on its posterior surface and insensible in front. The difficulty of observing 

 the phenomena which follow its stimulation in living animals has rendered 

 it impossible to determine the limits of its excitability and sensibility as 

 exactly as has been done for the different portions of the cord. 



It is also somewhat difficult to determine whether the action of the me- 

 dulla itself, in its relations to motion and sensation, be crossed or direct. As 

 regards conduction from the brain, the direction is sufficiently well shown 

 by cases of cerebral disease, in which the paralysis, in simple lesions, is on 

 the opposite side of the body. 



The action of the medulla as a reflex nerve-centre depends upon its gray 

 matter. When this gray substance is destroyed, certain important reflex 

 phenomena are instantly abolished. From its connection with various of 

 the cranial nerves, one would expect it to play an important part in the 

 movements of the face, in deglutition, in the action of the heart and of vari- 



