their' mode of action. 409 



been addedj when treated with lime so as to set free 

 their ammonia, emit an odor most closely resembling 

 that of corpses, or the peculiar smell of dunghills. 



By evaporating acids in air containing gaseous 

 contagions, the ammonia is neutralized, and we thus 

 prevent further decomposition, and destroy the pow.- 

 er of the contagion, that is, its state of chemical 

 change. Muriatic and acetic acids, and in several 

 cases nitric acid, are to be preferred for this purpose 

 before all others. Chlorine also is a substance which 

 destroys ammonia and organic bodies with much 

 facility; but it exerts such an injurious and prejudi- 

 cial influence upon the lungs, that it may be classed 

 amongst the most poisonous bodies known, and 

 should never be employed in places in which men 

 breathe. 



Carbonic acid and sulphuretted hydrogen, which 

 are frequently evolved from the earth in cellars, 

 mines, wells, sewers, and other places, are amongst 

 the most pernicious miasms. The former may be re- 

 moved from the air by alkalies ; the latter, by burn- 

 ing sulphur (sulphurous acid), or by the evaporation 

 of nitric acid. 



The characters of many organic compounds are 

 well worthy of the attention and study both of phys- 

 iologists and pathologists, more especially in relation 

 to the mode of action of medicines and poisons. 



Several of such compounds are known, which to 

 all appearance are quite indifferent substances, and 

 yet cannot be brought into contact with one another 

 in water without suffering a complete transformation. 

 All substances which thus suffer a mutual decompo- 

 sition, possess complex atoms ; they belong to the 

 highest order of chemical compounds. For example, 

 amygdalin, a constituent of bitter almonds, is a per- 

 fectly neutral body, of a slightly bitter taste, and 

 very easily soluble in water. But when it is intro- 

 duced into a watery solution of synaptas, (a constit- 

 uent of sweet almonds,) it disappears completely 

 without the disengagement of any gas, and the wa- 



35 



