competent to effect the disturbance of its electric equilibrium. M. Du Bois Reymond has stated, that, when the hands are immersed in two basins of water, in communication with the coil of a very delicate galvanometer, and the muscles of one arm suddenly contracted, a current of electricity is developed, and is detected by the movement of the magnetic needles. These researches have been repeated and varied by M. Despretz, who made a report upon them to the French Academy. He found that when a cylinder of platinum, or any other metal, in communication with a galvanometer, was held in each hand, and the fingers of one hand suddenly contracted, so as to grasp the cylinder tightly, the needles of the instrument immediately deviated often as much as 90°. The galvanometer he employed was exceedingly delicate, its wire coil being composed of 1800 convolutions. Unfortunately the sources of fallacy in these very delicate researches are so numerous, that it is scarcely possible to guard against error; and M. Becquerel has expressed his belief that the action of the cutaneous perspiration on the metals of the conductors, will explain these imaginary muscular currents. I confess that I cannot think this conclusion quite just; for when the conductors are held lightly in the hands, no current is detected; it is only when the muscles of one arm or hand

are violently contracted, that the galvanometer needles indicate the disturbance of electric equilibrium.

Although not immediately connected with the subject now under consideration, I could not without regret avoid drawing the attention of the members of the College to the very ingenious and, to my mind, very probable suggestion made eight-and-thirty years ago by our present illustrious president, regarding what may be denominated a mode of economising a portion of the animal heat. From a series of experiments, he found that, as a general rule, the capacity of the fluid excretions for caloric was less than that of the blood from which they were secerned; in other words, that a smaller amount of heat was required to raise them to the same temperature. He thus rendered it probable that, whenever the liver separated bile, and the kidneys urine, from the blood, these new fluids, although possessing the same temperature as the pabulum from which they were formed, yet really contained a less abstract proportion of caloric, and, as a necessary result, a certain amount of heat would be rendered sensible, and must materially aid in preserving the temperature of the body. This opinion, alike remarkable for its beauty and simplicity, has been most unaccountably overlooked by most late writers on physiology, for the experiment on

which it was based remains unaffected by the sources of error which have been shown to invalidate the nearly cotemporaneous hypothesis of Dr. Crawford.

In concluding my remarks on the physiological relations of electricity, I feel that, although a probable, yet by no means a positive, case is made out for its being regarded as the nervous agent, simply from the fact that we have not yet actually intercepted it in its presumed route through the nerves; still, I do not think that all the objections which have from time to time been urged against such a view are by any means tenable. We do not contend for the existence of currents of high tension in the body, and hence the objection that nervous force is stopped by placing a ligature on the nerve, whilst electricity is not, falls to the ground; for, as I have already shown, such currents, if of low tension, and the nerve circulated, are really thus stopped by a ligature. Another objection appears at first sight more plausible: if the trunk of a nerve be divided in a living animal, we know that the limb to which it is distributed becomes paralysed. It has been said that, if the vis nervosa and electricity were identical, the paralysis ought to disappear on uniting the divided ends of the nerve by means of a piece of wire or other conductor of electricity, which is well known not to be the

case. In reply to this and other such objections, the same answer may be given, that it is true, that, although we can prove the existence of electric currents in many of the tissues of the body, yet it is not contended that such currents are really absolutely identical with vis nervosa, but all that is assumed is, that they bear to each other the relation of cause and effect. When an electric current traverses this helix of wire it makes the iron bar placed in its centre a powerful magnet; yet no one contends that electricity and magnetism are, as forces, one and the same thing, but merely that they bear to each other the ratio of cause and effect. If I connect the magnet thus made with another bar of iron by means of a copper wire or any other conductor of electricity, it does not render it magnetic. Nor does any one express surprise at this; because, although electricity can traverse such a conductor, the new force we have developed, magnetism, cannot. Yet this is an analogous case to the objection urged against the idea of nervous force being generated by electricity, because we cannot renew it in a paralysed limb by uniting a divided nerve by means of a piece of wire. I confess I have a presentiment that one of the greatest philosophers of the age was correct when he remarked, if magnetism be a higher relation of force than electricity, nervous power may be one still more exalted and within

the reach of experiment. I am willing to admit that we do not possess a tittle of evidence to prove the existence of electric currents in the nerves themselves, although we know most positively that such currents exist in most other of the animal tissues, and that, further, in certain cases, their existence depends upon the integrity of the nerves: witness the cessation of the gastrohepatic current upon the division of the pneumogastric and sympathetic nerves. Taking for a moment the analogy presented by the electromagnet, a current of electricity of low tension traverses a wire arranged at right angles to the long axis of a bar of soft iron, and it instantly becomes a magnet of immense power. In an instant you see the bundle of iron wire suspended over the bars before me start as it were into life, and, after a few hasty vibrations, assume a fixed position over the poles. There is no visible connection between them; and yet, if I forcibly press one end of the bundle of wire, I feel an obstacle to moving it; and on resuming the force applied, it instantly returns to its position. On allowing the current to cease, the induced power vanishes, and the suspended wires obey the tension of the thread. There is, in fact, a radiant power emanating from the ends of these bars when the electricity traverses the wire coil. The directions of such lines of force are beautifully pointed