Every experiment and observation, which has been made upon the subject of nutrition, and of the reproduction of parts, clearly demonstrates that nerves and muscles, in common with every other part of the body, derive their structure from the arteries; and it is evident, that upon this structure their several properties must in some measure depend. But M. Galvani’s discovery of a subtile influence, which may be transmitted apparently from one part of an animal to another through foreign media, may reasonably give rise to a conjecture that the phenomena exhibited by nerves and by muscles may perhaps depend more immediately upon some such influence; and reasons exist, which might induce some to suspect that even this is derived from the blood. _Experiments suggested by some opinions of M. Fontana._ From the greatest number of experiments, perhaps, ever made by one physiologist, M. Fontana has been led to conclude, that the venom of the viper, opium, and several other poisons, which he examined, produce no effects whatever, when applied immediately to nerves and muscles alone, but that they destroy life, by exerting their influence upon some subtile principle existing in the blood. Independent of the experiments, published by M. Fontana, on this subject, his opinion respecting the existence of such a principle may be thought to receive no inconsiderable countenance, from the opinions of Harvey and of Mr Hunter, concerning the life of the blood, and from those experiments, by which Mr Hewson has demonstrated, that changes are instantaneously produced upon the coagulability of the blood, by passions of the mind, and whatever else affects the action of the heart and arteries. An experiment made by Dr Alexander of Halifax, and published at this place in the year 1790, in his excellent Thesis, ‘De partibus corporis quae viribus opii parent,’ may at first appear a sufficient refutation of M. Fontana’s opinion. He found that thirty three drops of a strong solution of opium in water, injected into the jugular vein of a large rabbit, destroyed it, as in M. Fontana’s experiments, in four minutes and a half; whereas, the same quantity injected into the crural vein in each leg of another rabbit, with an interval of twenty six minutes between the two injections, although it rendered the animal sleepy and stupid for a few hours, did it no material or permanent injury. Hence, Dr Alexander concludes, that the opium, injected into the jugular vein, did not destroy the animal by acting upon the blood alone, since if it had, the same effect, should have been produced, by introducing an equal quantity into any other vein of the body; but a quantity double of that, which had occasioned death when introduced into the jugular vein, failed to occasion it when introduced into the crurals.