Toxicology is that division of Forensic Medicine which takes into consideration the modes and actions of poisons upon the living body, the treatment of their effects upon the body, and the methods of detecting them when occasion requires. =Definition of a Poison.=--Neither the law nor medicine defines a poison. The popular definition is to be avoided, viz., that, a poison is a substance capable of acting injuriously on the body when taken or administered in a small dose. Husband defined a poison as “_any substance which, introduced into the system or applied to the body, is injurious to health and destroys life, irrespective of temperature or mechanical means_.” Taylor and Stevenson define a poison as “_a substance which when absorbed into the blood is, by its direct action, capable of seriously affecting health or destroying life_.” There are substances, however, which do not require absorption into the blood in order to exert their deleterious action, _e.g._ the corrosive acids and alkalies; but, although the chief action is a local one in most cases, some absorption does take place and is evidenced in systemic effects, and are so classified as poisons differing from powdered glass, which acts mechanically only and is not a poison in the true sense of the word. Winter Blyth considers that “_a substance of definite chemical composition, whether mineral or organic, may be called a poison if it is capable of being taken into any living organism, and causes, by its own inherent chemical nature, impairment or destruction of function_.” According to Luff a poison is “_a substance which, either by its direct action upon the skin or mucous membranes, or after its absorption into the blood, is capable of injuriously affecting health or destroying life_.” Letheby defines a poison as “_anything which otherwise than by the agency of heat or electricity is capable of destroying life, either by chemical action on the tissues of the living body, or by physiological action from absorption into the system_.” The law does not recognise the manner in which the substance acts, nor the result; the legal standpoint is the _intent_ of the administrator qua administrator. The law is as follows: “_Whosoever shall administer or cause to be administered or taken by any person any poison or other destructive thing with intent to commit murder shall be guilty of a felony_” (24 and 25 Vict. c. 100, sec. 11). Section 22. “_Whosoever shall unlawfully apply or administer to or cause to be taken by, or attempt to apply or administer to, or attempt to cause to be administered to or taken by, any person, any chloroform, laudanum, or other stupefying or overpowering drug, matter, or thing, with intent, in any of such cases, thereby to enable himself or any other person to commit, or with intent, &c., to assist any other person in committing any indictable offence, shall be guilty of felony._”