284 . Scientific Proceedings (116). 



4. Blood Pressure. — In all of the animals a striking fall in blood 

 pressure was observed, the extent of the fall depending in a measure 

 on the amount of the drug injected. There was partial, but 

 never complete return to the former pressure level. 



5. Degree of Contraction. — -There was always an increase in the 

 height of the stroke recorded by the lever, the increase ranging 

 from 16 to 162 per cent. A point was always reached after which 

 further introduction of the drug caused diminution in volume out- 

 put. The increase in cardiac contraction occurred simultaneously 

 with the fall in blood pressure, but persisted and often continued 

 after partial restoration of the blood pressure level. Unlike the 

 augmentation accompanying the fall in pressure induced by 

 histamine or hemorrhage, the increase produced by quinidin is 

 usually due to greater muscle shortening, not to diastolic relaxa- 

 tion. The persistence of effect likewise indicates a direct stimulat- 

 ing action on the heart muscle. The relation of the fall of pressure 

 to the height of contraction is, however, not finally determined by 

 these experiments. 



6. Threshold for the Production of Auricular Fibrillation by 

 Faradization. — In four experiments this was slightly raised; in 

 four others, there was no demonstrable change. 



7. Effect on Premature Contractions. — In one animal frequent 

 spontaneous ventricular premature contractions were noted. 

 These disappeared after the injection of quinidin. 



8. Mode of Death. — Only one animal died with ventricular 

 fibrillation. In the others, there was progressive slowing of the 

 heart, sometimes with the occurrence of sino-auricular block. 

 The auricles, as a rule, ceased before the ventricles. In the final 

 curves were seen isolated, orderly ventricular beats. 



9. Lethal Dose. — The lethal dose (mg. per kg.) was extremely 

 variable. In general, the greater the fractionation of dosage, the 

 greater was the amount of drug necessary to cause death. 



Experiments dealing with the effect of quinidin on the rate of 

 conduction of the excitation wave through heart muscle are in 

 progress. 



