An equally devoted pursuer of the same branch of science was the late Dr. Marshall Hall, whose name posterity will rank with those of Harvey, Hunter, Jenner, and Bell. During the whole course of his long and useful life he was a most careful and minute observer; and no fact, however apparently insignificant, escaped his attention. His important discovery of the diastaltic nervous system, by which his name will long be known amongst scientific men, originated in an exceedingly simple circumstance. When investigating the pneumonic circulation in the Triton, the decapitated object lay upon the table; and on separating the tail and accidentally pricking the external integument, he observed that it moved with energy, and became contorted into various forms. He had not touched a muscle or a muscular nerve; what then was the nature of these movements? The same phenomena had probably been often observed before, but Dr. Hall was the first to apply himself perseveringly to the investigation of their causes; and he exclaimed on the occasion, “I will never rest satisfied until I have found all this out, and made it clear.” His attention to the subject was almost incessant; and it is estimated that in the course of his life he devoted not less than 25,000 hours to its experimental and chemical investigation. He was at the same time carrying on an extensive private practice, and officiating as lecturer at St. Thomas’s Hospital and other Medical Schools. It will scarcely be credited that the paper in which he embodied his discovery was rejected by the Royal Society, and was only accepted after the lapse of seventeen years, when the truth of his views had become acknowledged by scientific men both at home and abroad.