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Such stimulation, however, Pilcher and Sollmann believe may be secondary to asphyxia. Nicotin they found to cause intense stimulation of the vasomotor center. Ergot and hydrastis and its alkaloids seem to have no effect on the vasomotor center. Strophanthus acted on this center only moderately, and digitalis very slightly, if at all.
Again a psychologically different effect and yet one often to be preferred results from mild stroking movements, the stroke always to be repeated in the same direction, never up and down. The slow change in the position of the tactual sensations evidently produces a rather strong influence on the equilibrium of nervous impulses, and here again vasomotor reflexes seem to arise easily.
Clearly, then, a restricted area of the brain may, through the controlling influence of the vasomotor nerves, be flushed with arterial blood while neighboring parts remain relatively anaemic.
It may be added that exactly the same tendency to superficial and arrested respiration takes place whenever there is any intense mental concentration, as in severe intellectual work. The arrest of respiration tends to render the blood venous, and thus aids in stimulating the vasomotor centers, raising the blood-pressure in the body generally, and especially in the erectile tissues.
At length, after much work with acids, filtration, and distillation, we determined that a neurotic had been employed, and that its action on the vasomotor system of the nerves was very similar, if not identical, with nitrate of amyl. Further than that, even Tatham, expert in such matters, could not proceed.
Just what creates the intense desire for tobacco to the habitue has not been quite decided, but probably it is a combination of the irritation in the throat, especially in inhalers; of the desire for the rhythmic puffing which is a general cerebral and circulatory stimulant; for the increased vasomotor tension which many a patient feels the need of; for the narcotic, sedative, quieting effect on his brain or nerves; for the alluring comfort of watching the smoke curl into the air or for the quiet, contented sociability of smoking with associates.
Except during the stage when the person is becoming used to the tobacco habit, in which stage the heart is weakened and the vasomotor pressure lowered by his nausea and prostration, the blood pressure is almost always raised during the period of smoking.
Witness the charm of the neuropathic eye with its widely dilated pupil that changes with each emotion, the mobile face, delicate, with a play of color, red and white, that is charming to look at, but which the grim physician calls "Vasomotor instability." There is nothing neutral about this type; she is either very lovely or a freak. So all advice in the matter is of little avail.
Also, atropin sometimes quiets cardiac pain, but it will not steady the heart, may irritate it, and will increase vasomotor tension, although peripheral nerve irritation may be diminished. Hence a fair dose of morphin hypodermicaly with a small dose of atropin, if respiratory depression is feared, is a physiologic method of bettering the condition.
Camphor in doses large enough to cause convulsions stimulated the vasomotor center. In smaller doses it generally stimulated the center moderately, but not always. Even when this center was stimulated, however, the camphor did not necessarily increase the blood pressure. The rise in blood pressure from epinephrin is due entirely to its action on the peripheral blood vessels and the heart.
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