574 



THE NERVOUS SYSTEM 



from below upward as high as the point of origin of the phrenic nerves. In 

 amphibia, the brain has been all removed from above, and the cord removed 

 as far as the medulla oblongata from below; yet so long as the medulla oblon- 

 gata was left intact, respiration and life were maintained. But if the medulla 

 oblongata is wounded, particularly if it is wounded in its central part oppo- 

 site the origin of the vagi, the respiratory movements cease, and the animal 



FIG. 382. Diagram of Ascending Conduction Paths from the Cord through the Medulla 

 and the Thalamus to the Cerebral Cortex. (Cunningham.) 



dies from asphyxiation. This effect ensues even when all parts of the 

 nervous system except the medulla oblongata are left intact. 



Injury and disease in men are accompanied by the same nerve disturb- 

 ances as are exhibited by these experiments on animals. Numerous in- 

 stances are recorded in which injury to the medulla oblongata has produced 

 instantaneous death; and, indeed, it is through injury to it, or of the part of 

 the cord connecting it with the origin of the phrenic nerves, that death is 

 commonly produced in fractures attended by sudden displacement of the 

 upper cervical vertebrae. 



