The phenomena of sleep and coma as the result of a poison acting as a depressant of motor nerve force afford food for some interesting speculations, which, however, as more concerning the psychologist, the writer can only glance at here. It is evident that in the highest of psycho-motor centres, the organs of thought and of consciousness, the paresis of the lower centres assumes the form of sleep, and paralysis that of coma. Sleep, as a partial, and coma, as a complete, obliteration of thought and consciousness must, therefore, be intimately connected with motor nerve function, sleep being a reduction, coma a suppression of the function, or a suspension of thought. Ideation, to use J. S. Mill's very appropriate term for the thought process, appears to be effected by motor nerve currents or, at all events, to be accompanied by them and suspended with their suspension. The thinking principle, the nous within us, is no doubt more than mere nerve action, but it can, apparently, not manifest its presence without motor nerve cells in healthy action. Every thought, though not synonymous, is evidently synchronous with a current of motor nerve force, and it is not improbable that, by means of these currents, that silent transference of thought is effected from brain to brain, which modern psychology has demonstrated to be not only possible but actual under certain conditions. But further speculation on these interesting mysteries it would be out of place here to indulge in.
F. Action on Sensory Centres and the Reflexes.
The sensory sphere remains comparatively unaffected in mild cases, and in the early stages of more serious ones, but when paresis has deepened into paralysis, sensation becomes ever more blunted, and with the advent of coma, of course, quite extinct. Reflexes, both superficial and deep ones, are also completely abolished at this period of the poisoning process, and the nerves of special sense do not react against any, even the strongest possible stimulation. The eye stares vacantly into a glaring light held close before it, and the widely dilated pupil shows no sign of reaction. The ear also appears deaf to any noise, and strong ammonia vapour is inhaled through the nose like the purest air, whilst pricking, beating, and even burning the skin elicit not a quiver of a muscle.