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Rh is under the control of the will; but, at the same time, it may be excited to discharge by drugs that act on the nervous centres. Thus strychnia throws the muscles of an animal into terrible tetanic convulsions by acting on its nervous centres; but it causes a torpedo to discharge a quick succession of shocks till the creature is exhausted. Again, an electric organ shows fatigue, and it needs time to rest and recover. Lastly, the organ is the seat of chemical changes.

There are many other phenomena that time will not permit me to mention. If we could get a supply of live torpedoes or of electric eels, and have some means of keeping them alive, I can conceive a course of Christmas lectures of surpassing interest; or we might get over the difficulty of having the live animals in the lecture-room by delivering the lectures in Cairo instead of in London, where no doubt the thunderer would be willing to show his powers. May we, however, hazard an explanation of the nature of these organs and of their relation to muscle and gland? In the case of torpedo, gymnotus, and the skate, the nerve ending is evidently analogous to