Some interesting experiments on this point have been recently performed by Professor Miller and Dr. Sticker. The former cele brated physiologist observes,t " It was known that, after the division of a nerve, the portion cut off from communication with the brain retains, for a certain time, its excitability; but the question, how far the continuance of the connection with the brain and spinal marrow is necessary for the longer preservation of the irri tability of the nerves, and whether the muscles retain their irritability when their nerves no longer communicate with the central parts of the nervous system, could not hitherto be an swered with certainty, and had indeed been seldom mooted. Nysten had asserted that the muscles of patients who died a short time after an apoplectic seizure preserved their irratibility, and contracted under the influence of the gal vanic stimulus, although the functions of the brain had been paralyzed.
" I had good reasons, however, for believing that, in such cases, the nerves retain their power only for a short time, losing it entirely after a longer interval; for, in experiments on the re production of the nervous tissue in a rabbit, I had once observed, that the lower portion of the nervus ischiadicus, which I had divided some months previously, had lost all its exci tability; and a similar fact had been before ob served by Fowler. I have since performed, in conjunction with Dr. Sticker, new experiments, which have completely confirmed that suppo sition. To prevent the regeneration of the nerves, and to withdraw more effectually the lower portion from the influence of the brain and spinal cord, a portion of the nerve (the ischiadic) was entirely removed. The experi ments were made only on two rabbits and a dog; yet the results were so constant, that they are quite worthy of dependence.
" Eleven weeks after the division of the nerve in the first rabbit, it was laid bare in its course between the biceps and semitendinosus muscles. Contrary to expectation, and to our mortification, the continuity of the nerve was found to be restored. It was divided anew below the cicatrix ; and it is remarkable that, although the animal uttered a loud cry, the section excited no contraction of the muscles. The lower portion of the nerve was now ex posed to the galvanic stimulus of a single pair of plates, was cut and pulled in every possible way, but not the slightest muscular contraction was excited.
" For the sake of comparison, the nerve of the opposite side was divided, when the animal showed signs of suffering the most severe pain, and violent muscular spasms took place ; and, after the division, very slight irritation of the nerve itself, that is to say, of the lower portion of it, or merely of the muscles, excited strong twitchings, even after death.
" Ten weeks after the division of the nerve in the dog, the ends were found to be reunited. The experiment was performed exactly as in the rabbit, and the result, as to the effect on the nerve, was entirely similar : it had lost all its excitability; but the muscles still contracted slightly when stimuli were applied directly to them immediately after death : however, this remaining irritability was gone, while, in the muscles of the opposite leg, the strongest con tractions could be excited.
" Five weeks after the nerve had been di vided in the second rabbit, we proceeded to examine its state, and were the more interested on account of the short time that had elapsed since its division. The ends were not united ; they were somewhat swollen, and connected with the surrounding cellular tissue. In the other instances, the portion of nerve removed measured about four lines only; here its length was eight lines. No contraction of the muscles could be excited by irritating the nerve either mechanically or by a chemical stimulus, caustic potash, or by galvanism ; nor by irritating the muscle itself, although the rabbit had plenty of vital power. On the left side the muscles were found irritable, as in the other cases, both before and after death.
" The foregoing experiments prove, at least, that when the communication of the nerves with the brain is wholly cut off, they gradually lose the power of exciting the muscles to con traction, while the muscles lose their irritability. The result would, however, have been still more decisive if, in place of a single pair of plates, a small galvanic battery had been em ployed to stimulate the nerves and muscles. That, and that alone, would have enabled us to determine with certainty whether all the power of the muscles, in two of the cases, had been lost. The experiments as they were made, however, prove distinctly enough the necessity of communication with the brain for the pre servation of nervous and muscular power. We may from them conclude also that if, after the division of a nerve, the excitability of the lower portion, and the irritability of the muscles are restored, the nerve has itself been completely reproduced ; and that this has not been the case if the nerve and muscle do not retain their vital properties." I may here observe, that an experiment, si milar to those of Professor Muller and Dr. Sticker, in which Sir Astley Cooper assisted the late Dr. Ilaighton, was made in this coun try many years ago, but never published. The sciatic nerve was divided in a dog. In a few days the lower portion had lost its power of exciting muscular contraction.