but it appears from the experiment of Mr Kite, that this is by no means the case, when the functions of the brain are suspended by hanging, or drowning[12]. Dr Whytt’s experiment on this subject is one of the most decisive with which I am acquainted. He found, that opium operates much more slowly in destroying the heart’s motion in frogs, deprived of their brain and spinal marrow, than it does when these animals ate entire. Several of my own experiments, though not made expressly with this view, gave the same result with those of Dr Whytt. M. Fontana tells us, he has discovered the heart of the wheel polypus to be a voluntary muscle. It was probably this discovery which led him to try the effects of his will upon his own heart. For the success of his experiment, we have the testimony of his friend Dr Gerardi, Professor of Anatomy in the University of Parma, who, in a very learned little Dissertation on the Origin of the Intercostal Nerve, published in the Journal de Physique for September last, makes the following short mention of it; ‘Je ne dois point oublier de vous dire que M. Fontana a la faculté d’accélérer, ou de retarder à volonté son pouls, sans aucune contraction sensible des muscles.’ The direct experiments, by which I was first led to adopt the opinion that the heart might be affected by the mechanical irritation of its nerves, were made upon very young cats and rabbits; some with the assistance of my friend Dr Physick, now settled in Philadelphia; others in presence of several other gentlemen studying at this university. It appeared very decidedly from two or three of these experiments, that the contractions of the heart were quickened by irritating the brain at the origin of the spinal marrow. In others again, the result was by no means so clear. But it should be recollected that the evidence of one accurate, and positive experiment, is not in the least invalidated by twenty unsuccessful ones, especially upon animals of warm blood; where the irritability of their muscles is so very fleeting, and the result liable to variation from so many, as yet, unknown causes. The irritability of the arteries, for example, is now completely established, yet Haller’s experiments led him to deny it. And even those of the accurate Verschnir, to whom we are indebted for unquestionably the best series of experiments upon this subject, failed of success (as we are told by Dr Dennison, in an excellent Thesis confirming their truth,) when repeated before some of the Faculty here. Immediately, therefore, on discovering the superior powers of zinc, and molybdena, in exciting contractions, I began again to repeat with these metals the experiments on the nerves passing to the hearts of frogs; but for a long time without satisfying either myself, or others, whether any effect was really produced. At length, however, I was so happy as to succeed completely. On the 18th of March last, in presence