Hence, we are almost driven to accept the pituitary and pineal glandular bodies as the separate organs, which separately produce the two necessary reagents, they being the only glandular bodies whose position would enable them to perform this function. This hypothesis is substantially supported by the position of these organs in the center of the cerebrum and their anatomical structure and connection with the sensory tracts.
The fact that these organs are exceedingly small, weighing only a few grains, is more in favor of the hypothesis than against it, because the actual quantity of energy involved and needed in brain operation, as compared with that involved in muscular operations, is exceedingly minute. The actual quantity of nervous energy required to maintain the conscious state in a human being for a period of twelve hours, if expressed as mechanical energy, would probably be less, possibly very much less, than the millionth part of a horsepower minute.
It is on these grounds that we base the hypothesis that these two small cerebral glandular organs are the factories which produce the chemical reagents whose combination is necessary to evolve the nervous energy which gives to the cerebrum its power of cognition, its power of maintaining the conscious state, its power of using the nervous system as a means of communication for obtaining cognitions or knowledge of external relations, and all of its powers of cogitation, cognition and re-cognition of internal relations. These are the principal, if not the only functions of the cerebrum.
Returning now from our digression to the pituitary and pineal organs, these bodies, like many other parts of the living body, like all parts, except the involuntary organs, are unable to operate continuously. The involuntary vital organs, heart, lungs, etc., apparently never tire of their work; never need a period of idleness, in which to recuperate. But this is not true of voluntary organs, processes and functions. It is not true of the power of cognition, of the power of maintaining the conscious state.
***Excerpt from Charles John Reed: The Law of Vital Infusion and the Phenomenon of Consciousness