I9I4.] CRILE— THE KINETIC SYSTEM. 267 



the destructive phenomena are felt, the kinetic speed is high and hfe 

 is on a sensuous edge. Not only is there a seasonal rhythm to the rate 

 of flow of energy, but there is a diurnal variation, the ebb is at night, 

 and the full tide in the daytime. This observation is verified by ex- 

 periments which show that certain organs in the kinetic chain are 

 histologically exhausted, the depleted cells being for the most part 

 restored by sleep. 



We have seen that there are variations in speed in different spe- 

 cies, and that in the same species speed varies with the season of the 

 year and with the time of day. In addition there are variations also 

 in the rate of discharge of energy in the various cycles of the life of 

 the individual. The young are evolved at high speed for growth, so 

 that as soon as possible they may attain to their own power of self- 

 defense ; they must adapt themselves to innumerable bacteria ; to 

 food, and to all the elements in their external environment. Against 

 their gross enemies the young are measurably protected by their 

 parents; but the parents — except to a limited extent in the case of 

 man — are unable to assist in the protection of the young against 

 infectious disease. 



The cycle of greatest kinetic energy for physiologic ends is the 

 period of reproduction. In the female especially there is a cycle of 

 increased activity just prior to her development into the procreative 

 state. During this time secondary sexual characters are developed — 

 the pelvis expands, the ovaries and the uterus grow rapidly, the 

 mammary glands develop. Again in this period of increasing speed 

 in the expenditure of energy we find the thyroid, the suprarenal and 

 the hypophysis also in rapid growth. Without the normal develop- 

 ment of the ovary, the thyroid and the hypophysis, neither the male 

 nor the female can develop the secondary sexual characters, nor do 

 they develop sexual desire nor show seasonal cycles of activity, nor 

 can they procreate. The secondary sexual characters — sexual de- 

 sire, fertility^may be developed at will — for example, by feeding 

 thyroid products from alien species to the individual deprived of the 

 thyroid. 



At the close of the childbearing period there is a permanent 

 diminution of the speed of energy discharge, for energy is no longer 

 needed as it was for the self-preservation of the offspring before 



