But there still remains another source of fallacy connected with these experiments, to which considerable importance has been attached. It has been said that the acrid humours ejected from the stomach of a person labouring under a _spontaneous_ disease, may kill an animal. _Morgagni_[207] relates a very remarkable instance, in illustration of this fact. A child having died of a fever was opened, when a quantity of green bile was found in the stomach, which changed the colour of the scalpel to violet; having dipped the point of the knife into this bile, two pigeons were wounded with it, and they soon died in convulsions. The bile was then mixed with some bread, and given to a cock, which also died in the same manner. From this general view of the subject before us, the forensic physician will be enabled to appreciate its just value, and to apply the indications it may furnish, in each particular case, without the risk of error. In some instances such experiments may prove nothing, in others they may afford only equivocal results, but which may add something to the general weight of circumstantial evidence; while others, again, may furnish proofs so unquestionable, as to leave no doubt upon the subject; such was the case in the instance of _Michael Whiting_[208], who was convicted of administering corrosive sublimate to his brothers-in-law, when it appeared in evidence that a portion of the poisoned dumpling was given to a sow, who in consequence became sick, and remained ill for several days.
We have now disposed of the several questions connected with the subject of poisoning, which must be regarded, in their forensic relations, as being of the highest importance. In considering the subjects, generally, there must necessarily remain doubts, many of which will be considerably diminished, or entirely removed, upon their application to particular cases; still, however, the nature of medical evidence upon such occasions must be frequently regarded as only sustaining high probabilities, and the professional witness may exclaim with _Hoffman_[209] “_Ardua sane provincia ei imponitur cui determinandæ ejusmodi quæstiones exhibentur._”
Poisonous substances have been very differently arranged by different authors, each appearing to have adopted a classification best suited to promote the particular views and objects of his own pursuit; thus, the botanist and chemist, engaged in the examination of the physical characters by which poisons may be individually distinguished and identified, have very judiciously erected their system upon the basis of natural history. The pathologist, whose leading object is the investigation of the morbid effects which follow the administration of these agents, with equal propriety and justice prefers a classification deduced from a generalization of the symptoms they are found to occasion; while the physiologist, who seeks to ascertain through what organs, and by what mechanism they destroy life, may be reasonably expected to arrange the different poisons under divisions corresponding with the results of so interesting an inquiry.