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 *firmed it by many appropriate experimental facts,—namely, that the salts of the same base produce the same actions, independently of the acids with which they are combined. The law, however, is a more general one, as given above, and was stated in former editions of the present work. It applies not only to bases, but likewise to acids, such as the hydrocyanic, oxalic, arsenious, and arsenic acids, and also to neutral organic principles which act through the blood, such as picrotoxin, colocynthin, elaterin, and narcotin.

The same author considers it to be also a probable conclusion from a variety of experiments on the salts of various bases, that ''those salts which are isomorphous, or possess the same crystalline form, are closely allied in action''.

4. The effect of mixture depends partly on the poisons being diluted. Dilution, by prolonging the time necessary for their being absorbed, commonly lessens their activity; yet not always; for if a poison which acts through the blood is also a powerful irritant, moderate dilution will enable it to enter the vessels more easily: a small dose of concentrated oxalic acid acts feebly as an irritant or corrosive; moderately diluted, it quickly enters the blood and causes speedy death. The effect of mixture may depend also in part on the mere mechanical impediment interposed between the poison and the animal membranes. This is particularly obvious when the mass containing the poison is solid or pulpy; for then the first portions of the poison that touch the membrane may cause an effort of the organ to discharge the rest beyond the sphere of action,—if, for example, it is the stomach,—by vomiting. The effect of mixture in interposing a mechanical impediment is also well illustrated where the substance mixed with the poison is a fine, insoluble powder, capable of enveloping its several particles. Thus it is that small, yet poisonous doses of arsenic may be swallowed and retained with impunity, if mixed with finely powdered charcoal, magnesia, and probably cinchona-bark, or the like. Besides diluting and mechanically obstructing their application, the admixture of other substances may alter the chemical nature of poisons, and so change their action.

It is important to keep in view, that the influence of mixture may be exerted in consequence of the cavity into which a poison is introduced being at the time filled with contents. Some of the most powerful and unerring poisons may in such circumstances altogether fail to produce their usual effect, if speedily vomited. Thus Wibmer notices the case of a man, who swallowed an ounce and a half of arsenic after a very hearty meal, had merely a severe attack of vomiting with subsequent colic, and got quite well in four days. And a still more pointed instance has been briefly mentioned by Dr. Booth of Birmingham, where an ounce of corrosive sublimate was swallowed after a full meal without any material ill consequence, vomiting having been speedily induced.