450 INDUCTION. 



These three sets of instances admit of heing treated accord- 

 ing to the Method of Agreement. In all of them the metallic 

 compounds are brought into contact with the substances which 

 compose the human or animal body ; and the instances do not 

 seem to agree in any other circumstance. The remaining 

 antecedents are as different, and even opposite, as they could 

 possibly be made ; for in some the animal substances exposed 

 to the action of the poisons are in a state of life, in others 

 only in a state of organization, in others not even in that. 

 And what is the result which follows in all the cases ? 

 The conversion of the animal substance (by combination 

 with the poison) into a chemical compound, held together 

 by so powerful a force as to resist the subsequent action 

 of the ordinary causes of decomposition. Now, organic life 

 (the necessary condition of sensitive life) consisting in a 

 continual state of decomposition and recomposition of the 

 different organs and tissues ; whatever incapacitates them for 

 this decomposition destroys life. And thus the proximate 

 cause of the death produced by this description of poisons, 

 is ascertained, as far as the Method of Agreement can 

 ascertain it. 



Let us now bring our conclusion to the test of the Method 

 of Difference. Setting out from the cases already mentioned, 

 in which the antecedent is the presence of substances forming 

 with the tissues a compound incapable of putrefaction, 

 (and a fortiori incapable of the chemical actions which con- 

 stitute life,) and the consequent is death, either of the whole 

 organism, or of some portion of it ; let us compare with these 

 cases other cases, as much resembling them as possible, 

 but in which that effect is not produced. And, first, " many 

 insoluble basic salts of arsenious acid are known not to 

 be poisonous. The substance called alkargen, discovered 

 by Bunsen, which contains a very large quantity of arsenic, 

 and approaches very closely in composition to the organic 

 arsenious compounds found in the body, has not the slightest 

 injurious action upon the organism." Now when these 

 substances are brought into contact with the tissues in 

 any way, they do not combine with them ; they do not arrest 



