Belladonna, stramonium, and Indian hemp likewise produce congestion of the brain and wakefulness. The latter, under the name of hashish,[137] is still used in the East to bring on a state of delirium, and, if rumor is to be credited, has its votaries in this country. Tea and coffee act in a similar but far less powerful manner. As one of the results of experiments with these substances, instituted upon myself, I found that the circulation of the blood was rendered more active.[138] Their influence in preventing sleep is well known to the generality of people, and this effect is doubtless entirely due to their action upon the heart and blood-vessels by which the amount of blood in the brain is increased. In persons of fair and thin skins, who are not accustomed to the use of either of these beverages, the face can be seen to flush after they have been taken; and I have frequently met with persons in whom their use was always followed by suffusion of the eyes, and a feeling of fullness within the head. Their power to increase the force and brilliancy of our thoughts, and to sustain the mind under depressing influences, has long been recognized, and is to be ascribed to the same cause as that which prevents sleep. * * * * * 4th. _Wakefulness is also caused by functional derangements of certain organs of the body, whereby an increase in the amount of blood in the brain is produced._ Under this head are embraced those cases of sleeplessness due to exalted sensibility of the nervous system. They are chiefly met with in persons of feeble constitution. The slightest impression made upon the skin, or any other organ of sense, is converted into a sensation out of all proportion to the exciting cause. There is thus a condition of general hyperæsthesia which greatly tends to the prevention of sound and refreshing sleep. The following case illustrates very well the phenomena of the state in question: