110 THE ROYAL SOCIETY OF CANADA 



erature of -12° for an hour, but not exposure to -14° for the same 

 period. This winter we decided to carry out further experiments. But 

 before proceeding to a description of our results it will be convenient 

 at this stage to consider also some experiments which have been carried 

 out on the limit of temperature which can be survived by different 

 exsected organs of the frog. 



Of. the numerous experiments which have been carried out with 

 frog's muscle only the more recent need be mentioned. According to v. 

 Bunge * frog's muscle is irritable between the temperatures of + 40° and 

 -4 • 0°C. Heubol f exposed and ligatured frog's hearts (emptied of blood) 

 and froze them to complete rigidity within 30 seconds with ether spray. 

 In experiments in which the temperature varied between -1° and -3°C. 

 over a period of from 5 minutes to an hour, the hearts recovered and 

 commenced to beat after removal ' of the sinus-ligature, and refilling 

 of the ventricule with blood. Jensen and Fischer | have shown by ex- 

 periments on the gastrocnemius of R. esculenta that exposure to a 

 temperature of -1° until the greater part of the "free water" was frozen 

 produced little damage; further cooling affected to greater and greater 

 degree the irritability and conductivity of the muscle, which as a rule 

 fell to zero at -3°, the temperature at which, according to these authors, 

 the fast-bound water of the muscle (das festes gebundene Wasser des 

 Muskels) begins to separate. 



Very accurate experiments have been carried out recently by H 

 Brunow, working in Jensen's laboratorj^* In these experiments the 

 temperatures were measured exacth'- by thermoneedles fixed into the 

 muscles. The duration of each experiments was between 15 to 30 

 minutes. Brunow summarises his results as follows: 



"The isolated Gastrocnemius of R. fusca survives a temperature 

 of — 2-9°C., without completely losing its irritability. The death-point 

 lies at -3'0°C., just as in the case of R. esculenta. 



"With lower temperatures rigor mortis sets in immediately after 

 thawing, and more i-apidly the lower the muscle has been cooled. 



"The muscle of R. fusca remaining in the animal and normally 

 perfused survived a temperature of -4*06° and was still irritable after 

 thawing. Its death-point lies between -4-1° and -4-2°C. 



"Perfused muscle therefore survives a temperature at least one 

 degree lower than does isolated muscle." 



*Lehrbuch dcr Physiologie des Menschen, Leipzig, 1901, Bd. I, S. 308. 



f'Die Wiedcrbelebung des Hcrzens nach dem Eintritt volkommener Ilerz- 

 muskelstarre." Pfluger's Arcliiv., 45, .503 ff. 1889. 



f'Der Gefriertod dcr Muskcln," Zentralb. f. Physiol., 23, 297, 1909. 



* Inaugural Dissertation: "Der Kaltetod des isolierten und durchbhiteten 

 Froschmuskels." Gottingen, 1912. 



