The human psychism, possessed of notable complexity, has as its forerunners other organic forms conditioned by nature’s macrocycles, such as the seasons and the passage from day to night. Numerous variations modify the psychism’s internal and external conditions. There are variations of temperature, luminosity, as well as the climatic changes of each season. All organisms are subject to a greater or lesser degree to the determinism of the natural cycles. The human being is not as conditioned as other species by organic cyclicity, and its psychism achieves modifications and an ever-increasing independence. A very clear case is the exercise of sex, which, in contrast to the other species, is independent of the seasonal cycles.
In the mechanisms of consciousness. there are different rhythms, as demonstrated by the diverse bioelectric discharges that show up in the electroencephalogram. The centers have their own particular rhythms and the levels of consciousness have evident work cycles. When vigil completes its time of daily work, it “lowers” its activity and one begins to enter the period of sleep. Thus the period of sleep compensates the period of vigilic work. The metabolic cycles and the general vegetative rhythms operate within the mechanics of the different levels of consciousness.
The human being’s major cycle is given by the vital time, which is completed as the individual goes through the different existential stages: birth, childhood, adolescence, youth, first and second maturity, elderliness, senectitude and death. In each stage there is a transformation of the psychism according to organic needs, interests, possibilities offered by the environment, etc. Finally, the psychosomatic cycles and rhythms show important modifications, in accordance with the changes of direction that take place at the moments when each vital stage begins, and declines.