It has from time immemorial been generally believed, that no proof of poisoning is more satisfactory than that which is furnished by the effects produced upon dogs, by their swallowing the contents of the stomach of persons who are supposed to have died from poison. Writers on Forensic medicine have, however, adduced several objections to the validity of such a test; some of which are undoubtedly worthy of consideration, while others are the deductions of a theory which receives no support from experience. In the first place it has been stated, that substances poisonous to man, will not always occasion deleterious effects upon animals[204]; this, to a certain extent, is undoubtedly true; some of the _Ruminantia_ appear to be less sensible to the operation of narcotic plants, than carnivorous animals. _Aloes_ are injurious to dogs and foxes. Oxen are said to eat the _Philandria Palustris_, which is pernicious to horses; but we are very much inclined to believe that a poison sufficiently powerful to destroy the life of a man, would if administered in the same state of concentration, destroy that also of an inferior animal. It is in smaller doses only that the difference in the action of such bodies upon various animals becomes evident and appreciable. This opinion is confirmed by numerous experiments. _Mr. John Hunter_, in his evidence[205] on the trial of _Donellan_, in answer to the question, whether any certain conclusion can be drawn respecting the poisonous operation of a substance upon man, from its effects upon an animal of the brute creation, replied, “_As far as my experience goes, which is not a very confined one, because I have poisoned some thousands of animals, they are very nearly the same; opium, for instance, will poison a dog similar to a man; arsenic will have very near the same effect upon a dog, as it would have, I take it for granted, upon a man; I know something of the effects of them, and I believe their operations will be nearly similar._” If any farther confirmation of this opinion were required, how extensively and satisfactorily has it been afforded by the late experiments of _M. Orfila_.[206] _Mr. Hunter_ also, on the memorable trial above mentioned, explained a source of fallacy which attends such experiments upon animals; he is asked “whether there are not many things which kill animals almost instantaneously, that will have no detrimental or noxious effect upon a human subject, such, for instance, as spirits?” He replies that a great deal depends upon the manner of conducting the experiment, and that by forcing an animal to drink, the liquor often passes into the lungs. See _Appendix_, _p._ 272. _Orfila_, in his valuable work on poisons, instituted a series of experiments upon this subject, with the intention of determining the value of an experiment so generally accredited; from which he is led to conclude, 1st. That the practitioner should never attempt by force to make an animal swallow the suspected