CHAPTEE XXV 

 SALTS OP THE HEAVY METALS 



Iw general the action of the salts of the heavy metals may he 

 described as local and systemic or general. 



Local Action. With the exception of the salts of Arsenic and 

 Antimony, the local action of the heavy metals is due to the fact that 

 they form chemical compounds with the proteids of the tissues with 

 which they come into contact. 



When solutions of dissociable salts of heavy metals are added to 

 proteid solutions, a precipitate of the albuminate of the metal is 

 formed. This precipitate may be a dense, tough, insoluble mass 

 in some eases, or in others it may be less dense, and soluble in an 

 excess of the proteid. (Salts of mercury.) Those which form in- 

 soluble precipitates only destroy tissues when in strong concentra- 

 tion and consequently serve as superficial caustics, while in dilute 

 solutions they are astringents. On the other hand, those which 

 penetrate deeply are powerful caustics but not astringents. 



The salts of the heavy metals produce their astringent action in 

 one of three ways, according to Dixon — " The sohible salts of the 

 metals may form albuminates and liberate free acid ; the metal may 

 be locally absorbed, so constricting the part, and reducing the secre- 

 tions; and lastly, insoluble salts like those of Bismuth may cover 

 and mechanically protect the surface." 



The local action is largely due to the dissociated metal or 

 metallic oxide ion, although the salts of the stronger acids owe part 

 of their action to the acid set free when the salt combines vrith the 

 proteid, because in this combination an albuminate is formed and 

 the acid freed. This action is more noticeable when strong solutions 

 are used and may be so pronounced as to make the action more irri- 

 tant than astringent. 



A certain tolerance to the corrosive action may be acquired if 

 small doses or weak solutions are used at first. This cannot be satis- 

 factorily explained l)ut may be well illustrated by the tolerance to 

 arsenic of the arsenic eaters of Tyrol. 



All metallic salts are antiseptic, due to their power of coagulating 

 the proteids of the bacterial cells. 



Systemic Action. This action depends upon the absorption of 

 the metals into the body and the fact that they must be absorbed 

 as the ion. .SoUmann says, "All metals are practically equal in 



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