514 THE NERVOUS SYSTEM. 



movements be uninterrupted. Life may also continue when 

 the spinal cord is cut away in successive portions from 

 below upwards as high as the point of origin of the phrenic 

 nerve, or in animals without a diaphragm, such as birds or 

 reptiles, even as high as the medulla oblongata. In Am- 

 phibia, these two experiments have been combined : the 

 brain being all removed from above, and the cord from 

 below ; and so long as the medulla oblongata was intact, 

 respiration and life were maintained. But if, in any animal, 

 the medulla oblongata is wounded, 'particularly if it is 

 wounded [in its central part, opposite the origin of the 

 pneumogastric nerves, the respiratory movements cease, 

 and the animal dies as if asphyxiated. And this effect 

 ensues even when all parts of the nervous system, except 

 the medulla oblongata, are left intact. 



Injury and disease in men prove the same as these ex- 

 periments on animals. Numerous instances are recorded 

 in which injury to the human medulla oblongata has 

 produced instantaneous death ; and, indeed, it is through 

 injury of it, or of the part of the cord connecting it with 

 the origin of the phrenic nerve, that death is commonly 

 produced in fractures and diseases with sudden displace- 

 ment of the upper cervical vertebra?. 



The centre whence the nervous force for the production 

 of combined respiratory movements appears to issue is in 

 the interior of that part of the medulla oblongata from 

 which the pneumogastric nerves arise ; for -with care the 

 medulla oblongata may be divided to within a few lines of 

 this part, and its exterior may be removed without the 

 stoppage of respiration ; but it immediately ceases when 

 this part is invaded. This is not because the integrity of 

 the pneumogastric nerves is essential to the respiratory 

 movements ; for both these nerves may be divided without 

 more immediate effect than a retardation of these move- 

 ments. The conclusion, therefore, may safely be, that 

 this part of the medulla oblongata is the nervous centre 



