INORGANIC POISONS. 351 



slightest injurious action upon the organism ; yet it contains a 

 very large quantity of arsenic, and approaches very closely in 

 composition to organic compounds. 



These considerations enable us to fix with tolerable certainty 

 the limit at which the above substances cease to act as poisons. 

 For since their combination with organic matters must be regu- 

 lated by chemical laws, death will inevitably result, when 

 the organ in contact with the poison finds sufficient of it to 

 unite with atom for atom ; whilst if the poison is present 

 in smaller quantity, a part of the organ will retain its vital 

 functions. 



All substances administered as antidotes in cases of poisoning, 

 act by destroying the power which arsenious acid and corrosive 

 sublimate possess, of entering into combination with animal mat 

 ters, and of thus acting as poisons. Unfortunately no other body 

 surpasses them in that power, and the compounds which they 

 form can only be broken up by affinities so energetic, that their 

 action is as injurious as that of the above-named poisons them- 

 selves. The duty of the physician consists, therefore, in his 

 causing those parts of the poison which may be free and still un- 

 combined, to enter into combination with some other body, so as 

 to produce a compound incapable of being decomposed or digested 

 in the same conditions. Hydrated peroxide of iron is an in- 

 valuable substance for this purpose. 



When the action of arsenious acid or corrosive sublimate is 

 confined to the surface of an organ, those parts only are destroyed 

 which enter into combination with it ; an eschar is formed, and 

 is gradually thrown off. 



Soluble salts of silver would be quite as deadly a poison as 

 corrosive sublimate, did not a cause exist in the human body by 

 which their action is prevented, unless their quantity is very 

 great. This cause is the presence of common salt in all animal 

 liquids. Nitrate of silver, it is well known, combines with ani- 

 mal substances, in the same manner as corrosive sublimate, and 

 the compounds formed by both are exactly similar in the character 

 of being incapable of decay or putrefaction. 



When nitrate of silver in a state of solution is applied to skin 

 or muscular fibre, it combines with them instantaneously ; ahi- 

 17 



