ACTION OF DIGITOXIN 419 



show the retardation. Do the two auricles beat in alternate 

 rhythms or synchronously? Does this hold true for the 

 ventricles also! Stimulate one vagus nerve from time to 

 time (do not injure the nerve by drying, etc., or by too 

 strong a current) and see if its connections with the heart 

 muscle are destroyed at any time. Inject more drug from 

 time to time until the second stage is well developed. Wait 

 then and do not give ami more drug unless it appears to be 

 absolutely necessary to bring on the last stages. 



When the stage of irregularity appears (third stage) ob- 

 serve carefully which chambers of the heart first take up 

 the rapid rhythm. Is this due to paralysis of the vagus 

 endings ! 



Caution: Sometimes the second stage of marked slowing is not developed 

 in the heart (inhibitory mechanism weakened or paralyzed) and the pulsations 

 take on a rapid character early in the intoxication and the stage of irregularity 

 may follow after a brief interval. Slow administration of the drug at first is 

 best calculated to bring on the stage of marked inhibition. 



When the heart becomes very irregular observe the cor- 

 responding changes in pressure. Watch for the sudden de- 

 velopment of delirium cordis (fibrillation) and note which 

 chambers first show this phenomenon. Do the other cham- 

 bers begin fibrillating at once or only after a considerable 

 interval ? How does delirium cordis affect the blood-pres- 

 sure? What can you say about delirium cordis in the frog 

 or turtle? 



Do you get satisfactory tracings from the heart showing- 

 all the stages of the poisoning! Do you believe it would be 

 possible to standardize digitalis preparations according to 

 the amount of the drug necessary to bring on the different 

 stages in the heart action ? On what do you base your con- 

 clusions! What is the cause of death in digitoxin poison- 

 ing! The administration of the drug should be continued 

 (at long intervals) until the animal dies which will prob- 

 ably be rather suddenly. Judging from your experiment 

 what should be the clinical symptoms of the first or thera- 



