Vi4 POISONS, CONTAGIONS, MIASMS. 



CHAPTER XV. 



On Poisons, Contagions, and Miasms. 



A great many chemical compounds, some derived from inorganic 

 nature, and others formed in animals and plants, produce pecu- 

 liar changes or diseases in the living animal organism. They 

 disturb the vital functions of individual organs ; and when their 

 action attains a certain degree of intensity, death is the conse- 

 quence. 



The action of inorganic compounds, such as acids, alkalies, 

 metallic oxides, and salts, can in most cases be easily explained. 

 They either destroy the continuity of particular organs, or they 

 enter into combination with their substance. The action of sul- 

 phuric, muriatic, and oxalic acids, hydrate of potash, and all 

 those substances which produce the direct destruction of the 

 organs with which they come into contact, may be compared to 

 a piece of iron, which can cause death by inflicting an injury 

 on particular organs, either when heated to redness, or when in 

 the form of a sharp knife. Such substances are not poisons 

 in the limited sense of the word, for their injurious action depends 

 merely upon their condition. 



The action of the proper inorganic poisons is owing, in most 

 cases, to the formation of a chemical compound by the union of 

 the poison with the constituents of the organ upon which it acts ; 

 it is owing to an exercise of a chemical affinity more powerful 

 than the vitality of the organ. 



It is well to consider the action of inorganic substances in 

 general, in order to obtain a clear conception of the mode of 

 action of those which are poisonous. We find that certain 

 soluble compounds, when presented to different parts of the body, 

 are absorbed by the blood, whence they are again eliminated 



