ACTION OF ACOXITINE 431 



few minutes) the heart suddenly goes into delirium cordis 

 and the pressure quickly falls to zero. It may be necessary 

 to give a little more of the drug to produce the final effects 

 within a sufficiently short time. 



*j 



How did section of the vagi affect the respiration ? What 

 Avas the very first abnormal action Avhich your animal 

 showed as seen in your tracing? Examine the respiratory 

 record closely. What general conclusions can you draw? 

 If the vagi had not been cut what would have happened to 

 the heart? If two or more experiments are performed at 

 the same time one group of students should cut the vagi, a 

 second group should give one milligram of atropine and a 

 third should let the action of the aconitine proceed without 

 interfering in any way. Immediately after the animal dies 

 open the chest quickly and see if the heart is fibrillating. 



EXPERIMENT CXXXVIL 



Aconitine. (Dog: Heart Tracings, Blood-pressure.) 



1. As in Experiment CXXX under digi toxin, arrange to 

 record blood-pressure and heart tracings from a dog. Place 

 aconitine solution (ten cubic centimeters equal one milli- 

 gram) in the burette. 



When a normal record has been taken then very slowly 

 and cautiously inject small repeated doses of aconitine. The 

 object is to bring on the action very slowly and to let 

 each phase of the heart reaction be fully developed. Watch 

 the chambers of the heart and see which ones first show ab- 

 normalities. Over what chambers of the heart do the vagus 

 nerves exercise the fullest control? Can you see any evi- 

 dence of this by watching the heart as the action of the 

 drug comes on? 



Do you get the stage of marked slowing as in the previous 

 experiment? Do the two auricles beat together or in dif- 

 ferent rlivthm? Is this true for the ventricles also? Does 



