266 CRILE— THE KINETIC SYSTEM. [April 22, 



shorn of its barbs, in an environment of powerful and hostile carni- 

 vora? And yet in such a hostile environment many unprotected 

 animals survive by their muscular power of flight alone. It is evi- 

 dent that the provision for the storage of " adaptive " energy is not 

 the only evolved characteristic which relates to the energy of the 

 body. The more the self-preservation of the animal depends on 

 motor activity, the greater is the range of variation in the rate of dis- 

 charge of energy. The rate of energy discharge is especially high 

 in animals evolved along the line of hunter and hunted, such as the 

 carnivora and the herbivora of the great plains. 



Influences That Cause Variation in the Rate of Output of 

 Energy in the Individual. 

 Not only is there a variation in the rate of output of energy 

 among various species of animals, but one finds also variations in the 

 rate of output of energy among individuals of the same species. If 

 our thesis that men and animals are mechanisms responding to en- 

 vironmental stimuli is correct, and further, if the speed of energy 

 output is due to changes in the activating organs as a result of adap- 

 tive stimulation, then we should expect to find physical changes in 

 the activating glands during the cycles of increased activation. What 

 are the facts? We know that most animals have breeding seasons 

 evolved as adaptations to the food supply and weather. Hence there 

 is in most animals a mating season in advance of the season of maxi- 

 mum food supply so that the young may appear at the period when 

 food is most abundant. In the springtime most birds and mammals 

 mate, and in the springtime at least one of the great activating glands 

 is enlarged — the thyroid in animals and in man shows seasonal en- 

 largement. The effect of the increased activity is seen in the song, 

 the courting, the fighting, in the quickened pulse and in a slightly 

 raised temperature. Even more activation than that connected with 

 the season is seen in the physical act of mating — when the thyroid is 

 known to enlarge materially, though this increased thyroid activity, 

 as we shall show later, is probably no greater than the increased 

 activity of other activating glands. In the mating season the kinetic 

 activity is speeded up ; in short, there exists a state — a fleeting state — ■ 

 of mild Graves' disease; in the early stages of Graves' disease, before 



