254 THE NERVOUS SYSTEM 



The columns of Coll are continuous with the funiculi 

 graciles. 



The columns of Burdach and the direct cercbellar fasci- 

 culi pass to the cerebellum through the restiform bodies of 

 the medulla. 



Functions. The functions of the medulla are (i) con- 

 duction, (2) reflex action, (3) to furnish centers for special 

 acts. 



i. As a conductor the medulla is absolutely necessary as a 

 means of connection between the brain and the cord. Sen- 

 sory impressions to and motor impulses from the brain 

 must all pass through by this route. 



As a reflex nerve center the medulla also resembles the 

 cord, though impressions reflected through this organ are 

 frequently much less simple than those reflected through the 

 cord. Reflex action in the medulla is dependent on (3), to 

 be noticed now. 



3. The most important center presiding over coordinated 

 movements is that for respiration. The encephalon may be 

 cut away down as far as the medulla, and life will continue 

 for a certain time. It is also true that the medulla itself may 

 be gradually cut away from above downward until a certain 

 point is reached, when respiration suddenly ceases. Likewise 

 the spinal cord may be cut away upward till this point is 

 reached, when the same results will follow. This is the true 

 respiratory center, and is situated at the site of origin of the 

 vagi. Its destruction is followed by an immediate suspension 

 of respiration and consequent death by asphyxia, though 

 there is no manifestation of the distress usually accompany- 

 ing this condition. The sense of want of air is simply lost. 

 There is one of these centers for each side, but they act syn- 

 chronously, being connected by commissural fibers. Probably 

 the usual mode of stimulation of the respiratory center is by 

 afferent impressions, but it may also be stimulated directly, 

 as by deoxygenated blood. Mutilation of the medulla, on 

 account of the presence of this center, is followed by the 



