THE PLETHYMOGRAPH 205 



Curare is injected into the femoral vein until the respirations 

 cease (see p. 200). Asphyxia is allowed to supervene by suspending 

 the artificial respiration (Fig. 62), but this is re-established before 

 the final fall in blood pressure sets in. What evidence does the result 

 furnish concerning the cause of the asphyxial rise in blood pressure? 

 (If satisfactory curare is not available, the asphyxia may be in- 

 duced by clamping the trachea. The results are, however, less 

 clear because of the respiratory convulsions). 



Finally, the renal nerves are cut, and, the immediate effect on 

 the kidney volume having been observed and explained, several of 

 the foregoing experiments are repeated. How do you explain the 

 alterations in the results? 



The anima 1 is killed by haemorrhage while the various tracings 

 are being taken. 



In one or other of these demonstrations the opportunity may 

 present itself of attempting the resuscitation of the animal by 

 intra-arterial transfusion with epinephrin. To effect this 

 a cannula, inserted in the central end of the carotid artery, is con- 

 nected with a burette containing warm isotonic saline solution, 

 which is allowed to flow into the artery. Artificial respiration is 

 also performed and after seme saline has transfused a few cubic 

 centimetres of adrenalin chloride is injected into the tubing which 

 connects the artery with the burette and the thorax is vigorously 

 massaged over the region of the heart. In a successful experiment 

 the blood pressure, recorded from the carotid on the opposite side 

 to that through which transfusion is being made, will be observed 

 to rise, at first passively because of the thoracic movements, and 

 later because of resumption of the heart beats. Once these have 

 started the blood pressure quickly recovers and the cardiac massage 

 may be suspended. Explain the mechanism of the resuscitation 

 and particularly how the epinephrin acts. Would intravenous 

 transfusion be of any avail in attempting the resuscitation after 

 complete stoppage of the heart beat? 



