Very interesting scientifically and suggestive practically is another correspondence which I believe to be new, between the mode of spontaneous activity in youth and that of labor in the early history of the race. One of the most marked distinctions between savage and civilized races is in the longer rhythm of work and relaxation. The former are idle and lazy for days, weeks, and perhaps months, and then put forth intense and prolonged effort in dance, hunt, warfare, migration, or construction, sometimes dispensing with sleep and manifesting remarkable endurance. As civilization and specialization advance, hours become regular. The cultured man is less desultory in all his habits, from eating and sleeping to performing social and religious duties, although he may put forth no more aggregate energy in a year than the savage. Women are schooled to regular work long before men, and the difficulty of imposing civilization upon low races is compared by Bücher[8] to that of training a eat to work when harnessed to a dog-cart. It is not dread of fatigue but of the monotony of method makes them hate labor. The effort of savages is more intense and their periods of rest more prolonged and inert. Darwin thinks all vital function bred to go in periods, as vertebrates are descended from tidal ascidian.[9] There is indeed much that suggests some other irregular rhythm more or less independent of day and night, and perhaps sexual in its nature, but not lunar, and for males. This mode of life not only preceded the industrial and commercial period of which regularity is a prime condition, but it lasted indefinitely longer than the latter has yet existed; during this early time great exertion, sometimes to the point of utter exhaustion and collapse, alternated with seasons of almost vegetative existence. We see abundant traces of this psychosis in the muscle habits of adolescents, and, I think, in student and particularly in college life, which can enforce regularity only to a limited extent. This is not reversion, but partly expression of the nature and perhaps the needs of this stage of immaturity, and partly the same instinct of revolt against uniformity imposed from without, which rob life of variety and extinguish the spirit of adventure and untrammeled freedom, and make the savage hard to break to the harness of civilization. The hunger for fatigue, too, can become a veritable passion and is quite distinct from either the impulse for activity for its own sake or the desire of achievement. To shout and put forth the utmost possible strength in crude ways is erethic intoxication at a stage when every tissue can become erectile and seems, like the crying of infants, to have a legitimate function in causing tension and flushing, enlarging the caliber of blood vessels, and forcing the blood perhaps even to the point of extravasation to irrigate newly growing fibers, cells, and organs which atrophy if not thus fed. When maturity is complete this need abates. If this be correct, the phenomenon of second breath, so characteristic of adolescence, and one factor in the inebriate's propensity, is ontogenetic expression of a rhythm trait of a long racial period. Youth needs overexertion to compensate for underexertion, to undersleep in order to offset oversleep at times. This seems to be nature's provision to expand in all directions its possibilities of the body and soul in this plastic period when, without this occasional excess, powers would atrophy or suffer arrest for want of use, or larger possibilities world not be realized without this regimen peculiar to nascent periods. This is treated more fully elsewhere.