The characteristic mental symptoms are not only formed at the last stage in the future generation but our forefathers had infested these symptoms from the very beginning during the acute stage of a disease. Any physical condition of the body, be it be healthy or unhealthy, has its associated mental condition. We have observed that different people behave differently in different kind of fevers.
All the curative activities as well as adjustment to the surrounding by the brain respond whenever there is some changed conditions. Not only in the case of diseases, but also during the normal living. It even tries to adjust the body conditions to minute temperature changes of surroundings. During dry summer, it helps the body to cool down through sweating. Even hunger, thirst, sleepiness etc are symptoms being produced by the same segment of the brain that create fevers, pains etc.
The mechanism to determine the act of changed condition is a process to compare the present body condition with the previous body condition. The present body condition is readily available to the brain but the blue print of previous body condition must have been preserved at some area of the body. Also, the brain keep updating the data of previous body condition by replacing it with the present body condition after a lapse of some critical time intervals. These critical time intervals are different for different act of the body.