such as tend to prove the impossibility or improbability of suicide:—9. To the existence of a motive or inducement on the part of the prisoner, such as his having a personal quarrel with the deceased, or a hatred of him,—his succeeding to property by his death, or being relieved of a burthen by it,—his knowing that the deceased was with child by him. Upon many of the particulars now enumerated, important evidence may be derived from the medical part of the investigation; and not unfrequently such evidence can be collected or appreciated only by means of a medico-legal inquiry. 1 and 2. On the first two articles, suspicious conduct or conversation on the part of the prisoner before the crime, and the possession or purchase of poison by him, little or nothing need be said. The medical witness may of course be asked whether the conduct or conversation proved betokens an unusual acquaintance with poisons and their effects. And his opinion may be referred to regarding the nature of suspected articles found in the prisoner’s possession. As to the purchase of arsenic under the false pretence of poisoning rats, it may be observed, that a great deal more stress is usually laid on such evidence than it seems to deserve; for there are few houses, in the country particularly, which are not more or less infected by them. On the other hand, too little weight is attached to the circumstance of the purchaser not having warned his household of poison being laid. Such conduct ought in my opinion to be accounted extremely suspicious; for so far as I have remarked, the fear with which unprofessional persons regard the common poisons is such, that I can hardly believe any master of a house would actually lay poison without warning the servants and other inmates of his having done so. 3. The next article, which relates to the proof of the administration of poison, will require some details. Direct proof of the administration of poison by the actual giver is very rarely attainable, that part of the transaction being for the most part easily concealed. The proof of this point is justly accounted, however, a very important part of the evidence; nay, on some recent trials in this country the prosecution has failed apparently for want of such evidence, although the case was complete in every other particular. It is generally constituted by a chain of circumstances, and these are often strictly medical, as will now be shown by a few examples.