SOURCES OF TERRESTRIAL ENERGY 



phosis is directly effected. To cite Dr. Carpen- 

 ter's conclusions, as epitomized by Mr. Spen- 

 cer : " The transformation of the unorganized 

 contents of an egg into the organized chick is 

 altogether a question of heat : withhold heat 

 and the process does not commence ; supply 

 heat and it goes on while the temperature is 

 maintained, but ceases when the egg is allowed 

 to cool. ... In the metamorphoses of insects 

 we may discern parallel facts. Experiments 

 show not only that the hatching of their eggs 

 is determined by temperature, but also that the 

 evolution of the pupa into the imago is simi- 

 larly determined, and may be immensely ac- 

 celerated or retarded according as heat is arti- 

 ficially supplied or withheld." The phenomena 

 thus briefly cited are to be classed under the 

 general head of organic stimulus — and in a 

 wide sense, one might almost say that all stim- 

 ulus is the absorption of vital energy which 

 was originally solar. Sunlight stimulates ani- 

 mals indirectly, as in the case of actiniae which 

 are made more vivacious when neighbouring 

 sea-weed, smitten by sunbeams, pours oxygen 

 into the water in which they move ; and also 

 in the case of hard-worked men who gain 

 vigour from the judicious use of vegetable nar- 

 cotics. The waves of motor energy which the 

 human organism absorbs in whiffs of tobacco- 

 smoke are but a series of pulsations of trans- 



333 



