8 4 8 



ANIMAL HEAT. 



Numerous observations have been made, chiefly by Pflliger and his 

 pupils, upon the effect of changes in external temperature upon the 

 respiratory exchange of animals in normal and abnormal conditions. 

 The results of some of the most important experiments will now be 

 given } 



It will be seen from the above table that the respiratory exchange 

 decreases with a rise in external temperature, until a point about 35 

 is reached, when an increase in the metabolism occurs. 7 The response 

 to a change in temperature is, in the case of small mammals, almost 

 immediate. 8 Thus, within two minutes of a change from 30 to 18, 

 a mouse increased its output of carbon dioxide by 74 per cent. ; within 

 one minute of a change from 33 0- 25 to 17'5 the increase was 60 per 

 cent. The response to an increase in temperature does not take place 

 so quickly ; thus, within two minutes of a rise from 18 to 34 '5, 

 the decrease in the output of carbon dioxide was 18 per cent. ; 

 within one minute of a rise from 17 to 32, the decrease was 5 

 per cent. The power of maintaining a constant mean temperature is 

 readily tested in this manner, as the following example will show 

 (Pembrey) : 



1 See also the preceding article on " Chemistry of Respiration." 

 * Ztschr.f. ioL, Miinchen, 1878, Bd. xiv. S. 57. 

 *Arch.f. d. ges PhysioL, Bonn, 1877, Bd. xiv. S. 92. 



4 Ibid., 1877, Bd. xv. S. 603. 



5 Ztschr.f. EioL, Munchen, 1878, Bd. xiv. S. 51. 



6 Arch de bioL, Gand, 1887, tome vii. p. 274. 



7 See also Page, Journ. PhysioL, Cambridge and London, vol. ii. p. 228 ; and 

 "Chemistry of Respiration," this Text-book, vol. i. p. 712. 



8 Pembrey, Journ. PhysioL, Cambridge and London, 1894, vol. xv. p. 401. See also 

 "Chemistry of Respiration, " this Text-book, vol. i. 



