Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

the one side is manifested on both sides alike. The mode of arrangement appears to vary in certain parts ; for instance, as in vision, as a very peculiar contrivance is seen in the commissure of the optic nerve. Here the two inner portions of each probably divide : the one part continues in its course, while the other crosses over to its neighbor. In this way the sum total of the field of vision is represented on each side of the brain. To a degree, therefore, it must be true that the actions of the body have a definite source in the gray matter of the brain, as anato- my and pathology show. From these facts we should expect that a severing of the pedunculi cerebelli on the one side would determine a motion towards the opposite — a fact which actually occurs ; " for of all the singular physiological effects which can be produced, there is none more remarkable or instructive than the continued whirling, revolving, or rolling motions of an animal thus injured," says a distinguished naturalist of the present day. If, then, (as it seems plausible to suppose,) the peripheric nerves of all the body and limbs are one pole, while the brain is the other pole, — i.e. the former the positive and the other the negative pole of the electro-nerve circuit, — we can in some measure see why the actual transition from pleasure to pain can be so near and sudden. An impression can be made on any part of the body with more or less pleasure to a certain pitch ; but beyond that point, pain immediately ensues, which, if suf- ficiently increased, can be followed with palsy: this, if in- creased still greater, can be followed with death. If a very minute or delicately thin piece of metal be placed in a glass tube, and a large electric current be now passed through it by bringing it in the circuit of an active battery, the metal will then be likely to be instantly dissolved, and the circuit might not be readily completed by that route again. Dr. Smee says that what is true in this respect of such a pole is true also of liquid poles, and of intervening fluids. Where repair is con- stantly necessary, as it is in the brain, a very strong impression would more than equal the ordinary supply; and this action through that delicate combination and medium might thus be stopped.