316 Canadian Record of Science. 



0. my das gave much the most pronounced and certain 

 results in my experiments on the marine turtles. 



In one instance, with a weak current, preliminary increase 

 in the rhythm occurred, followed by slowing and even 

 short stops of the heart. 



Prolonged alternate Stimulation of the Vagi. — The following 

 account of an experiment on this subject furnishes the case 

 of longest cardiac inhibition yet published : — 



Exp. — Chelonia imbricata, 2 feet long. 



12.32 p. m. 1. Stimulation of left vagus for 30 minutes, maintains 

 constant standstill ; then current withdrawn ; after a latency of 14 

 seconds, rhythm re-established after 1-2 minutes. (First stimula- 

 tion from 12.32 to 1.3 p. m.) 



2. At 1.5 p. m. Stimulation of right vagus till 2.10 p. m. ; after the 

 current withdrawn, a latency of 16 seconds before rhythm began. 



3. Stimulation of left vagus till 3.32 p. m. ; when current shut off. 



4. At 3.35 p. m. Stimulation of right vagus till 4.25 p. m. ; latency 

 30 seconds. 



5. Stimulation of left vagus, from 4.25 p. m. till 5.40 p. m., when 

 beats began to appear. 



Thus in all there was continuous inhibition of the heart for 

 more than six hours ; for the periods between the stimulation 

 of the right and left vagi were only of sufficient length to 

 ascertain that the heart would still beat, and in none of 

 these cases did the heart begin to pulsate while the current 

 was passing. It was, in fact, evident that the power of the 

 vagus was not exhausted. To this remark, the right vagus 

 at 4.26 p. m. is an exception, but in that case,the electrodes 

 were at once, on the appearance of a beat, transferred to the 

 opposite vagus. 



It will also be noted that the periods of latency, after the 

 stimulation ceases before a beat appears, lengthens with 

 each stimulation. 



Comparative inhibitory power of the two vagi. — The follow- 

 ing is the statement of the results in 8 cases : — 



Arrest of the heart with tJie induced current : 



Specimen I. Left vague, secondary coil \ over primary. 

 « Bight " " | 



" II. Left " " at 10 cm. from primary. 



Right " " 5 



