[cameron-brownlee] temperature AND THE FROG 83 



In a number of cases increased breathing was observed, and in 

 the experiments lasting several hours this may have produced marked 

 over-oxygenation. What would be the ultimate effect of this we can- 

 not say. 



Since the different systems separately appear not to be killed 

 under the conditions mentioned, and yet somatic death occurs, we 

 can only attribute this last to an interference with the machinery of 

 coordination between the different systems. Such machinery may 

 be nervous or chemical. The blood affords the most probable channel 

 for the latter. There is no apparent change in the blood though 

 accurate examination of the serum might reveal changes. 



It is tempting to assume that the coordinating mechanism affected 

 is connected with the central nervous system, but it must be remem- 

 bered that the central nervous system remains alive. We have 

 already quoted Becht's results on the heat paralysis of nerve, which, 

 he points out, always precedes that of muscle. The most noticeable 

 external effects in our experiments are on respiration (first a quicken- 

 ing and then a cessation) and heart-beat (similar results). Both of 

 these are probably produced through the central nervous system. 

 Neither is in itself a cause of death. The frog can live for a short 

 time with the heart removed, and, as we shall show elsewhere, can live 

 for several weeks immersed in water, with lung respiration stopped. 



It is to be noted that temperatures which cause unconsciousness 

 invariably prove fatal if maintained for a sufficient time. 



The experiments on R. clamitans indicate that this species is 

 subject to temperature limitations similar to those of R. pipiens. 



The experiments in water give a curve (plotting temperature 

 against time) similar to but steeper than that plotted from those in 

 air. The curve indicates a similar limiting temperature (continuously 

 maintained). We cannot explain the cause of the more rapid fatal 

 effect produced in water. The difference in the results for R. pipiens 

 and those obtained by Babâk and Amerling for R. fusca and R. escu- 

 lenta indicates considerable variation in the resistance offered to high 

 temperature by different species. 



The experiments on exsected muscle show the same important 

 relationship between temperature and time. The similarity of this 

 result for striped muscle and for the whole animal, in spite of the fact 

 that striped muscle survived somatic death in almost all the ex- 

 perim.ents recorded, does not lend support to the theory that the cause 

 of death of the animal is through the central nervous system. 



We cannot account for the cause of death of muscle at moderate 

 temperatures (25°-35°). It does not seem due to such heat-coagul- 

 ation of proteins as would produce heat-rigor at higher temperatures, 



