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Updated: June 6, 2025
Stimulation of this centre causes contraction of the blood-vessels. Severing the same part causes paralysis of the vaso-motor nerves and dilatation of the blood-vessels. The conditions of the brain that have been most clearly shown to influence the circulation, are those that can be proved to take an effect on this vaso-motor centre.
There is reason that we should give careful attention to the views of Heerfordt and Zirm, that obstruction to the venous outflow may be the effective cause of the disease. Zirm believes the venous plexus of the choroid is an essential part of the mechanism for the regulation of intra-ocular tension, the necessary vaso-motor control depending on nerve centers situated in the iris. Nerve Control
These phenomena indicate that either the anatomical seat or the mode of generation of emotion, is in closer connection with the cerebral vaso-motor centre than is the seat of ideas. From this positive stand-point we may be permitted to cautiously venture a little further, in the direction of a theory for the precise localization of the organs of emotion.
Such a course is the menstrual crisis, without which even the vaso-motor paralysis is usually unable to determine uterine hæmorrhage.
Again, if the stimulus is less than usual, the vessels dilate, and the supply to the part is increased. Now the vaso-motor center may be excited to increased activity by influences reaching it from various parts of the body, or even from the brain itself. As a result, the nerves are stimulated, and the vessels contract.
The original stimulus may be excessive, and hence necessarily followed by reaction. 2nd. Schiff has shown that galvanization of a cerebro-spinal nerve causes a dilatation of the blood-vessels in the vicinity, as if the vaso-motor force were overpowered by the excessive stimulation of the controlling nerves.
As the stimulation of the vaso-motor nerves causes contraction of the blood-vessels, so their exhaustion or paralysis causes relaxation of these same vessels, consequently, over-distension with blood; and, if the door to hæmorrhage be once opened by the existence of the menstrual nisus, an excessive flow of blood. Such vaso-motor paralysis may depend on one of three circumstances: 1st.
The last theoretical condition would be, excitement of the brain or spinal cord, in a manner analogous to what may be determined by a galvanic current, and followed, therefore, by the same consequence paralysis of vaso-motor nerves, and excessive dilatation of the blood-vessels.
At the very moment, therefore, that the uterine blood-vessels are dilated, and blood is being exhaled into the uterine cavity, an excessive stimulation of the vaso-motor nerves may cause the blood-vessels to contract; the flow is then temporarily arrested, the circulation in the uterus disturbed, and its muscular fibres thrown into cramps. Or the opposite event may occur.
Vaso-motor disturbances and contraction of the pupil on the right side may result from pressure on the sympathetic. Death may take place from rupture, or from pressure on the air-passage. [Illustration: FIG.
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