There is a popular notion that if the feet are cold the head must be hot, and by keeping the extremities warm with wraps the “blood is drawn from the head,” and its temperature reduced. Those who have on the one hand studied the phenomenon of fever, and on the other noted the physical condition of races and individuals who habitually leave the extremities unclothed, will know that this theory of the distribution of heat is only partially true. Heat depends on the due supply of nutrient elements to the tissues. It is the expression or result of the process of local feeding. If a part is active it will be heated. When the feet are left bare the complex muscular apparatus of the extremity, which in a stiff shoe scarcely works, is called into vigorous action, the arch of the foot plays with every step, and each toe performs its share in the act of progression. This promotes growth and calls for nutrition, whereby the heat is maintained; whereas if it be simply packed away as a useless piece of organism, no amount of external heat will warm it. Work is the cause and counterpart of heat throughout the body.
The same principle applies to the head. No amount of external cooling will reduce the temperature, no drawing away of the blood by artificial expedients will permanently relieve the sense or obviate the fact of heat if the organ within the cranium is excessively or morbidly active. The brain is a peculiarly delicate and complicated organ, requiring more prompt and constant nutrition than any other part of the body, because the constituent elements of its tissue change more rapidly than those of any other in proportion to the amount of exercise. Moreover, the brain is always acting during consciousness, and even in sleep it is seldom wholly at rest, as we know from the occurrence of dreams. The faculty of nutrition is highly developed in the organ or it could not so continuously, and on the whole healthily, discharge its functions, even when other parts of the body, or the system as a whole, are suffering from disease. When the head is heated there is nearly always a local cause for it, and the remedy must be addressed to the seat of the malady. The temporary expedient of “drawing away the blood” by applying heat to the extremities is useful as far as it goes, and may suffice to enable the organ to rid itself by the contraction of its blood-vessels from a surplus charge of this fluid, but in the absence of special causes the _reason_ of the “heat of head” is undue exercise or disturbance of nutrition in the brain itself. Perhaps the seat of the over-work and consequent heating may have been limited to a particular part of the head; for example, the apparatus of sight, or hearing, as when the head becomes heated by reading too long or in a strong light. The point to understand is that when the head is physically hot it is the seat of too much or disorderly nutrition, and either the amount of brain or sense-power exercised must be reduced or the mode of action changed, and the particular part of the apparatus of perception or thought which has been too severely taxed relieved.