CAUSES MODIFYING THE ACTION OF POISONS tered in a" large 'dose, produces a local corrosive action, and may result in instantaneous death from shock, but in a smaller dose it may prove fatal "by acting on the heart, while in still smaller doses it acts on the spinal nervous system and the brain. 2. Form.—Under this head will have to be considered—(a) Physical State; (b) Chemical Combination; (c) Mechanical Combination. (a) Physical State.—Poisons administered in the form of gases or vapours act at once and most energetically. Poisons in the form of solutions act much more rapidly than powders. Poisons in the form of solids act 'very slowly, because they are difficult to be absorbed and, in some cases, may prove quite harmless. (b) Chemical Combination.—The action of a poison depends upon the solubility or insolubility resulting from a chemical combination. Thus, silver nitrate and hydrochloric acid are both strong poisons when taken separately but, when combined, form an insoluble salt of silver chloride which is almost innocuous. Similarly, baryta X^ariuni dioxide) and sulphuric acid act as poisons, if administered separately but, in combination, form an insoluble salt, barium sulphate, which has "no poisonous Affects on the system. In the same way strong acids and alkalies, when administered together, are rendered inert by their neutralizing effect. 'It should be borne in mind that certain poisons which are almost " insoluble in water may become dissolved in the acid secretion of the stomach, and are then readily absorbed into the blood. For instance, lead carbonate, white precipitate and copper arsenite, which are insoluble in water, are thus rendered sufficiently soluble for absorption through the mucous membrane of the stomach. - - , r, - - ' (c) Mechanical Combination.—The' action of a poison may T>e altered very much if combined mechanically with inert substances. For instance, a small dose of a concentrated mineral acid produces a corrosive action, but the same dose, largely diluted with water, may be taken internally with impunity. A heavy poisonous powder, when mixed with water, will settle down at the bottom of a vessel, and the victim fails to take it; while it would have been swallowed had it been taken with a fluid of nearly the same specjfiq gravity as that of the powder. For this reason arsenic - is usually mixed with milk, tea, coffee or cocoa -\frhen administered < for homicidal pur- poses. Alkaloids, when taken with animal -charcoal, are rendered more or less inert. < *' , - 3. Mode of Administration.—The rapi<ilty of -the action of a poisdii depends upon the mode in which it is'intrdduced into the system. ThuSj a poison acts most rapidly when inhajed in;?a gaseous or vaporous form or introduced into the blood current by injection'into a-vein, V>y injection,-or by application to an o^en wound. < -Next in rapidity is the of a poison which is*applied to, a serous surface, niext when introduced i cellular tissue, and .a&ext when applied - to a mucous membrane. The rapid is the action of a poison applied to the- unbroken skin. In this case a drug dissolved in oil acts more rapidly than a watery solution. A poison ingested into the stomach acts more rapidly than when injected, into the rectum, since the absorptive power of the stomach and '- intestine is greater than that of'the large intestine and rectum. is eliminated a,s rapidly(as* it 4s absorbed, no poisonous to-occur*, On li^e/G^3^;teEtd, if, tfee irate of absorp^w of eliiiii&ation, rthe potsexk tei$fe % accumulate in 'the cumulative action. For, £xafmpfe, mercury, lead,.