[cameron-brownlee] low TEMPERATURES ON THE FROG 117 



greater surface, and in the subsequent experiments by the fact that they were nearer 

 the bottom of the freezing mixture, and probably subjected to a temperature lower 

 than that registered by the thermometer). The abdomen of the second frog was 

 not completely frozen but the frog never recovered. Stimulation showed one hind 

 limb irritable, the other dead. The heart was beating normally, and some of the 

 muscular tissue of the thorax was apparently normal. 



After two hours and ten minutes the external temperature of the remaining 

 frogs was — 7°C. (the atmospheric temperature being — 23°). The frogs were re- 

 moved, and one was examined immediately. The skin was frozen, but the muscular 

 wall of the abdomen was not frozen. Ice was found in abundance in the pericardium 

 and all round it, and also in the heart substance. The other frog had not recovered 

 after three hours. Examination showed that many of the reflexes were present 

 in the fore-part of the animal. The heart was beating. The hind limbs were dead. 



B. Experiments on exseded hearts. 



These were carried out on several hearts at a time; they were placed in a test 

 tube which was cooled by immersion in a freezing mixture. Temperatures were 

 taken with a mercury thermometer. 



Experiment 2. Jan. 30th. Two hearts were frozen in normal saline, and kept 

 for one hour between — 6° and — 7°C. After warming slowly to room temperature 

 there was no recovery. 



Experiment 3. Feb. 7th. Four hearts, moistened with saline, were frozen, 

 and kept for two hours at temperatures between — i • 75° and — 7°C. None recovered. 



Experiment 4. Feb. 6th. Four hearts were frozen in normal saline solution, 

 and kept for 2J hours at temperatures between — 3° and — 5°C. None recovered. 



Experiment 5. Feb. 11th. Three hearts were frozen in saline and kept for 

 two hours between — 3-5° and — 4-3°C. None recovered. 



Experiment 6. Feb. 11th. Three hearts were moistened with saline, frozen, 

 and kept for two hours between — 3 • 5° and — 4 ' 0°C. None recovered. 



Experiment 7. Mar. iSth. Three hearts were moistened with Ringer's solution, 

 and frozen. The temperature sank in 20 minutes to — 4°C., and the hearts were 

 observed to be beating feebly, the Ringer's solution being still imfrozen. Two 

 minutes later, freezing commenced and the temperature rose to — 1°, remaining 

 constant for 8 minutes, then sinking slowly. The hearts were kept at — 4° for one 

 hour. They were allowed to warm up to room temperature slowly, but none 

 recovered. (The observed temperature of supercooling was undoubtedly lower 

 than that of the heart substance.) 



Experiment 8. Mar. 13th. Four hearts, unmoistened, were frozen as usual, 

 and kept at — 4° for If hours. None recovered. 



Experiment 9. Mar. 18th. Four hearts, unmoistened, were frozen as usual, 

 and kept at -3° for two hours. None recovered. 



Experiment 10. Feb. 12th. Two hearts, immoistened, were frozen, and kept 

 for two hours at — 3°C. Neither recovered. 



Experiment 11. Feb. 12th. Two hearts were frozen in saline, and kept for 

 two hours between — 2-5° and — 3°C. After warming to room temperature, the 

 auricle of one heart commenced to beat feebly but regularly. 



Experiment 12. Feb. 22nd. Two hearts, unmoistened, were frozen, and kept 

 for two hours between — 2° and — 2o°C. Two hours after thawing the auricles 

 were beating quite \igorously and regularly, but the ventricles were not beating 

 and gave no response to stimulation. 



