In primary insomnia there is always an increase in the quantity of blood circulating in the brain. This is either absolute or relative. The former is the case when there has been no exhausting disease, hemorrhage, or other debilitating influence in operation, and while, though general good health exists, the amount of blood in the cranium is augmented; the latter, when from any cause the system has become reduced, and when, while this condition prevails, a temporary activity takes place in the cerebral circulation. The first may properly be called active, the latter passive insomnia. In the one there is more blood in the brain than is normally present; in the other, though there may be less blood than in health, the quantity is increased over the amount to which the brain has in a measure accustomed itself. Thus if we suppose the cerebral vessels of a healthy brain to contain ordinarily a pint of blood, and the amount to be increased to a pint and a half, and continued at this standard for several consecutive days, a state of active insomnia ensues. If, on the other hand, this pint should be reduced to a gill by any cause producing general debility, such as hemorrhage, starvation, or disease, and then by some exciting mental emotion, the excessive use of alcoholic liquors, or other influence acting for a considerable period, be increased to half a pint, a condition of passive insomnia would be produced--the latter condition resulting not from a disturbance of the normal relation existing between the _intra_ and _extra_ cranial blood, but of that which has been established by morbific causes, and to which the organism has become habituated. CASE III.--The following is a good example of the active form of morbid wakefulness: