The _theorie d'epuisement_ of Jaccoud (Erschopfungs-theoric) also denies the possibility of Brown-Sequard's idea of prolonged spasm of the vessels of the centres. It imagines that powerful peripheral excitements exhaust the irritability of the nerve, and through that of the centres, and induce a state of unimpressibility--analogous to that which exists in a nerve or nerve-centre, which is included in the circuit of a constant current. The nervous force is wasted, and, until an opportunity of repose is afforded to the centre, the faculty of impressibility cannot again revive. I must say that of these two theories I decidedly incline to that of Handfield Jones (though I imagine that in reality the cases are extremely rare, if there be any, in which the change in the centres is really only functional and non-organic), I prefer the idea of paralyzing shock to that of exhaustion from over-excitement, from a consideration of the nature of that form of peripheral influence which has been specially mentioned by authors as competent to produce this sort of "reflex" affections, namely, intense and persistent cold. It seems to me a mere abuse of words to speak of this as an agent that could exhaust the nerve by over-stimulation; it must surely exhaust it in a much more direct manner than this, namely by the direct physical agency of withdrawing heat from the nerve, and spoiling its physical texture, _pro tanto_. If such an effect as that which must thus be produced on the nerve, and through it on the centre, is to be looked on as a case of over-stimulated function, then, it seems to me, there is no meaning in language, and no possibility of attaining to clear ideas on the subject of nervous influence. NOTE III. ARSENICAL TREATMENT OF VISCERALGIÆ. Since writing the above chapter on the Treatment of Neuralgia, I have had two fresh and very striking examples, in private practice, of the power of arsenic to break the morbid chain of nervous actions in angina pectoris.