On wakefulness Author:William Alexander Hammond Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III. THE EXCITING CAUSES OF WAKEFULNESS. Every cause capable of increasing the amonnt of blood ordinarily circulating through the brain may give ri... more »se to wakefulness. As these causes are more or less under the control of the individual, it is important that they should be fully considered. An increased amount of blood is attracted to the brain, and wakefulness is produced: 1st. By long-continued or excessive intellectual action, or any powerful emotion of the mind.—Every organ of the body, the condition of which admits of being ascertained by ocular examination, invariably contains more blood in its tissues when in a state of activity than when its functions are temporarily suspended. We are hence, a priori, justified in assuming that the law is equally applicable to the brain, but we are not forced to rely entirely upon reasoning from analogy. It has been shown already that during sleep the circulation of blood within the cranium is at its minimum, both as regards quantity and rapidity, and that as soon as the individual awakes there is an immediate afflux of this fluid to the cerebral tissues. All of us are familiar with the facts that, during severe mental labor, or while under the influence of some exciting emotion, the vessels of the head and neck become distended, the head feels full, the face is flushed, and the perspiration of the parts in question is increased in quantity. Within certain limits the more blood there is in the brain the more actively its functions are performed, and so well known is this fact that some persons, who require to exercise the several faculties of the mind to an extreme degree, make use of stimulating ingesta for the purpose of accomplishing the object in view. A moderate degree of cerebral activity is undoubtedly beneficia...« less