RESPIRATION. 



bellum? Is the controlling respiratory centre, therefore, located 

 in the cerebellum ? 



3. Divide the upper part of the medulla by an incision between 

 the atlas and skull. Do the respiratory movements continue ? 



4. Divide the cord on a level with the origin of the seventh cer- 

 vical nerve. In the rabbit the respirations are altered but little, 

 since in this animal breathing is chiefly diaphragmatic. By this 

 section the thoracic muscles are cut off from the respiratory centre, 

 but the innervation of the diaphragm is still intact. Impulses are 

 still carried to the centre from the periphery by the intact vagus 

 nerves. Other afferent impulses are in the main cut off from the 

 centre by its isolation from the brain above and the cord below. 



5. Expose and cut both vagus nerves in the neck region. Note 

 the change in the character of the respiratory movements and the 

 disturbance of the respiratory rhythm. Are the respiratory move- 

 ments which still continue sufficient to sustain the life of the 

 animal ? 



Allow the first stages of asphyxia to occur. Then revive the an- 

 imal with artificial respiration continued for a short time. 



6. Place the central ends of the divided vagi on electrodes from 

 an inductorium set up for medium strong tetanizing currents. 

 Stimulate the vagi with this current, interrupted about thirty times 

 per minute. Stop the artificial respiration. Is the respiratory 

 rhythm re-established ? Compare the results obtained from this 

 experiment with those obtained through section and stimulation 

 of the vagi in former experiments. What conclusions can you 

 draw concerning the location of the respiratory centre and the 

 regulation of its rhythmic activity ? 



IX. CONDITION OF LUNG FOLLOWING SECTION OF BOTH VAGI. 



Narcotize and anaesthetize a rabbit. Under aseptic precautions 

 expose and cut both vagus nerves in the neck region. Sew up the 

 wound and return the animal to its cage. Make careful observa- 

 tions of the subject until death occurs, which will generally be 

 within forty-eight hours. Determine the cause of death at au- 

 ii [161] 



