104 THE BIOLOGY OF THE SEASONS 



planes of unconscious, instinctive, intelligent, and rational 

 life. 



The biggest fact in the Biology of Summer is perhaps the 

 most obvious one, that it is then that life comes nearest, or, 

 what comes to the same thing, is most exposed to the source 

 of all mundane energy the sun. Thus the Biology of 

 Summer has for its central problem the influence of heat 

 and light upon life. Now there is heat that burns, as we 

 see in the Steppe vegetation after the dry season ; and there 

 is light that kills, notably in the case of the disease germs 

 or Bacteria which a forenoon of clear sunshine destroys 

 so beneficently ; but the general fact, demonstrable by 

 numberless experiments, is that the heat and light of 

 Summer renew the energies of living creatures. Indeed, we 

 all depend from year to year on the power that green plants 

 have of inducing the sunlight to help them to make food 

 for us. 



At the very opposite end of the scale for there is a long 

 gamut of life from wheat plant to man is it not true that 

 seeking the sun and seeking more life are synonymous for 

 some of us ? It is well known that the pulse-register or 

 sphygmograph proves that the sunshine vivifies the system. 

 Quite irrespective of warmth and comfort, quite apart from 

 the delights of the holiday mood, of being free, of hearing 

 the birds sing, and seeing the flowers in bloom, the sunlight 

 quickens the pulse and man's life. 



" O solemn-beating heart 

 Of nature ! I have known that thou art 

 Bound unto man's by cords he cannot sever. 

 And what time they are slackened by him ever, 

 So to attest his own supernal part, 

 Still runneth thy vibration, fast and strong, 

 The slackened cord along ! " 



And if in man so often with a slackened cord the sun- 

 light still awakens response, how much more in the animals 



