S62 POISONS, CONTAGIONS, MIASMS. 



mal substances dissolved in any liquid are precipitated by it, and 

 rendered insoluble, or, as it is usually termed, they are coagu- 

 lated. The compounds thus formed are colorless, and so stable, 

 that they cannot be decomposed by other powerful chemical 

 agents. They are blackened by exposure to light, like all othei 

 compounds of silver, in consequence of a part of their oxide oi 

 silver being reduced to the metallic state. Parts of the body 

 united to salts of silver no longer belong to the living organism, 

 for their vital functions have been arrested by combination with 

 oxide of silver ; and if they are capable of being reproduced, 

 the neighboring living structures throw them off in the form of an 

 eschar. 



When nitrate of silver is introduced into the stomach, it meets 

 with common salt and free muriatic acid ; and if its quantity is 

 not too great, it is immediately converted into chloride of silver 

 — a substance absolutely insoluble in pure water. In a solution 

 of salt or muriatic acid, however, chloride of silver does dissolve 

 in extremely minute quantity ; and it is this small part which 

 exercises a medicinal influence when nitrate of silver is ad- 

 ministered : the remaining chloride of silver is eliminated from 

 the body in the ordinary way. 



Without solubility, or the power of being carried to every part 

 of the circulation, no substance possesses activity in reference to 

 the animal organism. 



The soluble salts of lead possess many properties in common 

 with the salts of silver and mercury ; but all compounds of lead 

 with organic matters are capable of decomposition by dilute sul- 

 phuric acid. The disease called painter's colic is unknown in all 

 manufactories of white lead in which the workmen are accustomed 

 to take as a preservative sulphuric acid lemonade (a solution of 

 sugar rendered acid by sulphuric acid). 



The organic substances which have combined in the living 

 body with metallic oxides or metallic salts, lose their property of 

 imbibing water and retaining it, without at the same time being 

 rendered incapable of permitting liquids to penetrate through their 

 pores. A strong contraction and shrinking of the surface is the 

 general effect of contact with these metallic bodies. But cor. 

 rosive sublimate, and several of the salts of lead, possess a pecu- 



