80 THE ROYAL SOCIETY OF CANADA 



These results, when plotted (time against temperature) give a 

 curve which is moderately regular, considering the small number of 

 experiments of long duration. The curve indicates that the highest 

 temperature at which R. pipiens can maintain life continuously is about 

 18° C, while continued exposure to a higher temperature will prove fatal. 



A few experiments have been carried out with specimens of 

 R. clamitans. 



Experiment 62. April 30th, 1915. A specimen was kept at 

 35° (35-0° to 35-2°) for one hour. On removal from the air-chamber 

 it was unconscious. The heart commenced to beat after one or two 

 minutes. The animal had not regained consciousness after 5 hours. 

 On opening the thorax the heart was found to have stopped. Tap- 

 ping caused it to recommence beating, which continued. The muscles 

 of the hind limbs were dead ; those of the fore limbs reacted to elect- 

 rical stimulation. 



Experiment 63. April 30th, 1915. The frog was kept at 

 34-0°-34- 2°C. for one hour. On removal the animal was unconscious. 

 The heart beat was vigorous, and stimulation through the skin gave 

 the usual results. There was no recovery after 2 nor after 12 hours. 



Experiment 64. May 2nd, 1915. Internal temperature 30-0°- 

 30-2° for one hour. The frog did not lose consciousness. 



Since the limits obtained in these three experiments are the same 

 as for R. pipiens for the same time, it is evident that similar con- 

 clusions can be drawn for the two species. 



III. experiments on exsected heart, muscle, and nerve. 

 In these experiments the exsected tissues were kept in modified 

 Locke solution, and in each experiment similar tissues were kept 

 in the same solution at room temperature for the same period of time 

 without deleterious effect. The experiments were carried out in 

 March, 1915 (except No. 8 of the muscle-nerve experiments, performed 

 on May 15th). 



A. Experiment with the Heart. 



Three hearts kept at 35° for one hour were all killed. Of six 

 hearts kept at 34° for one hour only one recovered. At 33° for one 

 hour, one of three recovered. The same result was obtained at 32°. 

 At 31° for one hour, five hearts out of six recovered their spontaneous 

 beat, while the sixth responded to stimulation. 



These results indicate that the same temperatures are fatal for 

 the heart as for the intact animal, and suggest a possible cause of the 

 death of the animal. That the cessation of the heart-beat is the 

 actual cause of death is however disproved by the numerous cases 



