MIDWINTER 129 



as well as retrospective reference; it is the crouch 

 before the leap. Many an organism has learned 

 the lesson, se reader pour mieux sauter. The 

 repose of winter gives us the rebound of spring. 



On the moor a few hundred feet lower down there 

 are scattered birch trees with bare limp branches 

 on the pendulous tips of which the sun has hung 

 diamonds; what a story they have to tell us of 

 the precarious tenure of peripheral organs (as the 

 birch leaves fell the grouse molted its claws!); of 

 the usefulness of surrendering vulnerable organs; 

 of the economy of the organism, for the leaves in 

 their withering gave back to the tree all that they 

 had that was worth keeping; and of the prepara- 

 tions made many months ago within the well- 

 protected buds for the foliage and flowers of the 

 distant spring. 



From the external aspect the big fact is that the 

 rate of chemical reactions is increased by rise of 

 temperature, since that means increase in the rate 

 of molecular movements. It is true that what is 

 called van HofFs Law of the effect of temperature 

 on chemical reactions does not seem to fit very 

 well for the changes that go on in living creatures, 

 probably because these are such heterogeneous 

 systems, in which physical and chemical processes 

 become intricately mixed up; but the broad fact 

 is that the effect of warmth is to increase, and the 

 effect of cold to decrease, the rate of vital activity 

 or metabolism. Moreover, in spite of glacier-fleas 

 and small creatures from hot springs, the great 



