302 



HUMAN BIOLOGY 



indicates the efficiency of the life process at any given tem- 

 perature. At the bottom the generahzed curve for the 

 growth of plants indicates that at 50°f. the ordinary plant 



O'F 5' 10' 15' Z.0' Z5' 30'-3S' W 45' so' SS' (O' ts' 70' JS' ^O' S5' ?0' ^S lOO'F 



Mental 

 Energy 



Mental and 

 Physical Energy 

 Combined 



Physical Energy 

 Health 



Absorption of 



Oxygen by 



Crayfish 



Rate of Fission 

 of Infusoria 



Growth of 

 Plants 



Fig. I. Mean Temperature and Vital Processes. 



(From Huntington's Civilization and Climate, ed. 3, Yale Univ. Press.) 



makes no growth; at S5° growth is very shght, and at 60° 

 slow; but at higher temperatures it rapidly increases and 

 reaches a maximum at 85°. Above that level the rate of 

 growth rapidly diminishes and the plants die if the tem- 

 perature for night and day together averages above ioo°f. 

 In this curve, as in the others of Figure i, all conditions of 

 humidity, air movement and sunHght have been averaged 

 together, so that they neutrahze one another, and the 

 resultant curve represents only the effect of temperature. 



