RESPIRATION. 



piration. Change in the pulse rate may also be observed by watch- 

 ing the pulsation of the carotid arteries or by feeling the cardiac 

 impulse on the chest wall. How are the respirations affected when 

 the blood going to the brain is warmed above the normal? How 

 is the heart-beat affected? What is the relation between heart- 

 beat, respiratory rate, and rise of temperature ? 



2. Cold. Disconnect the warm-water bottle from the tubes in 

 contact with the carotids, and substitute a receptacle containing ice 

 water. First, let the respiratory rate return to normal. Then 

 while a tracing is being taken, allow the cold water to flow through 

 the tubing in contact with the arteries. Note the effect upon 

 the respiration and the heart-beat. Compare the tracing obtained 

 through the cold application with that obtained when heat was 

 applied. 



What is the effect of warmed blood upon the respiratory centre ? 

 of cold blood upon the respiratory centre ? 



VII. EFFECT OF ANEMIA UPON THE RESPIRATORY CENTRE. 



1. Using the same animal as in the previous experiments, clamp 

 both carotids with artery clips. Is there any change in respiration 

 following the occlusion of both carotids ? If so, does this changed 

 respiration continue or does it soon return to the normal? Ex- 

 plain. Does occlusion of the carotids materially or permanently 

 diminish the blood supply to the brain? What is the collateral 

 circulation ? 



What would be the only way completely to cut off the blood 

 supply to the brain ? 



2. Tie both carotids as high up as practicable. Introduce a 

 glass cannula into each artery. Take a normal respiratory trac- 

 ing. While this is being taken, open the clips on both arteries and 

 allow the animal to bleed to death. Collect the blood in a grad- 

 uated cylinder and record the phenomena observed after the loss 

 of each additional 10 c.c. of blood. How much blood is lost before 

 the respirations are affected? In what way are the respirations 

 affected as hemorrhage continues ? 



[159] 



