378 SIR THOMAS R. FRASER AND MR ALISTER T. MACKENZIE ON 



three regular and complete contractions of the heart occurred in 30 seconds. Twenty- 

 four hours after decapitation (and 92 hours after the injection), sixteen regular and 

 uniform contractions of the heart were seen in 55 seconds ; in systole, the ventricle 

 did not become very pale ; in the diastolic phase, only the apex of the ventricle and a 

 portion at the base first became dark. This series of contractions was succeeded by 

 a pause in diastole for 2§- minutes ; then the auricles began to contract and to 

 distend the ventricle ; at first, the ventricle responded only by superficial and 

 imperfect contractions, but after about a dozen auricular contractions the ventricle 

 was beating regularly and well, and then another long pause followed. Twenty- 

 nine hours after decapitation, the heart was motionless in diastole ; then the auricles 

 began to contract and to distend the ventricle ; at first the ventricle responded to 

 this stimulation imperfectly, but by and by it resumed its contractions at the rate 

 of 18 per minute, synchronously with the auricles, and became quite pale in systole; 

 4 minutes afterwards, the rate of contraction, however, became slower and diastolic 

 pauses of irregular length occurred. General reflexes could still be elicited. Thirty- 

 three and a half hours after decapitation, the conditions were as last noted ; the 

 heart was observed to beat well for 11 minutes at 18 per minute and then to 

 become arrested in diastole. Thirty-six hours after decapitation, the heart was 

 beating at 18 per minute, with occasional pauses in diastole lasting for one or more 

 minutes. No further observations were made. 



In the next series of experiments the extract dissolved in Ringer's solution was 

 applied to the outer surface of the frog's heart, definite quantities of standard solutions 

 being instilled within the pericardial sac. The procedure was as follows : — The brain 

 was destroyed anterior to a line joining the posterior margins of the eyelids. The frog- 

 was then pinned down on its back and the heart was fully exposed without damaging 

 the pericardial sac. A small portion of the sac was removed with scissors from the 

 highest part, which was usually situated over the auriculo-ventricular junction. By 

 means of a hypodermic syringe, from which 100 drops of Ringer measured approxi- 

 mately 1 c.c, five or ten drops of one or other of the standard solutions used ( = 0'05 c.c. 

 and O'l c.c.) were instilled within the pericardial sac through the artificial opening. 

 During this process the cut edge of the sac was held with fine forceps and the upper 

 part of the sac gently raised from the surface of the heart. After the instillation, the 

 pericardium was not released until several contractions of the heart had distributed the 

 solution all over its surface. These quantities of fluid were easily retained within the 

 pericardial sac of frogs weighing 20 grams and upwards, and the heart's movements did 

 not cause the solution to overflow. 



In order to keep the tissues moist, the frog was laid on wet filter-paper and was 

 covered by a glass funnel. 



In similar experiments upon frogs without the application of any poison, it was 

 found that the heart's movements preserved their chief characteristics for 48 hours after 

 the heart was exposed — the contractions continued to be regular in time and to affect 



