From the preceding considerations we may, we think, conclude:
1st. That unless the brain and spinal cord had been already exhausted or on the point of exhaustion previous to the menstrual crisis, this alone would be insufficient to exhaust them.
2d. That the degree of exhaustion in the cerebro-spinal system, necessary to determine vaso-motor paralysis, is very great, and much transcends that likely to be induced by the mental exertion required in the ordinary curriculum of a girl's school.
3d. That therefore, when vaso-motor paralysis, as indicated by uterine hæmorrhage, has occurred apparently in consequence of such mental exertion, it is really due to some other conditions existing with this.
Of these we have already insisted upon two—sedentary position and deficiency of physical exercise.
Authors have less frequently analyzed the effects of another circumstance so often accompanying the intellectual exertions of school life, namely, the morbid emotional excitement that is incident either to the period of adolescence or to the injudicious educational régime. To precisely appreciate these effects, it will be necessary to push a little further the analysis already commenced, of the mode of activity exhibited by different portions of the brain during the evolution of thought or of emotion.
Among all the obscurities that overhang this subject, a few facts are, nevertheless, demonstrated. The first that concerns us is the existence of the vaso-motor centre, whose situation and functions have been already described. The second is the localization of the function of thought in the circumvolutions of gray matter on the surface of the cerebral hemispheres—fact that we have already assumed to be sufficiently demonstrated. The third class of facts include those, also insisted upon, that indicate a peculiar influence of the emotions upon the circulation and the vaso-motor nerves. In some cases these are stimulated, and the blood-vessels spasmodically contract, the cheek pales, the hands and feet grow cold, chills creep down the back—even nausea may occur from interference with the circulation of the brain; or else the cheek flushes, the temples throb, the heart beats more rapidly, when, from temporary paralysis of these same nerves, the blood-vessels are suddenly dilated.
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.
It is well known that at the base of the brain are collected certain masses of nervous matter, that constitute nervous centres or cerebral ganglia, that are in very intimate connection, on the one hand, with nerves of special sense, as the optic[42] and olfactory,[43] on the other with nerves of general sensation and motion.[44] To this intricate part of the brain, these centres, converge the nerve-fibres collected in the spinal cord and medulla oblongata, and from them radiate other fibres that pursue a divergent course, and finally terminate in the gray matter of the cerebral hemispheres. Thus, the brute impressions brought from the periphery of the body, are conveyed to special foci of concentration, thence to be transmitted to the gray matter at the surface of the brain, and become material for thought. Conversely, impulses generated in the nerve-cells devoted to the elaboration of thought, pass through these same intermediate stations before they acquire sufficient consistency to affect the motor-nerves, and, through them, the muscular osseous apparatus of the body. Before a sensory impression can become a thought, or a voluntary impulse express itself by motion, each must be converged toward these centres, whence it afterwards radiates, along divergent fibres, directed now above, to the surface of the brain, now below, on a longer course, to the surface of the body.