48 DR. R. ANGUS SMITH ON 



I have already published some of my ideas on that con- 

 dition of the atmosphere which may be called diseased. 

 I have not believed that carbonic acid and sulphuretted 

 hydrogen were capable of producing the results so fre- 

 quently attributed to them, but agreed rather with the 

 more ancient theory " of a conversive force in matter, to 

 change the nature of things, by turning them into its own, 

 when by immediate contact one body alters the properties, 

 and changes the natural inward form and constitution and 

 disposition of another, and works it to conformity to itself, 

 draws it into its own likeness, impressing its own cha- 

 racter upon it, and communicating to it its own form and 

 nature ^' *. 



In examining this subject, I passed air for several months 

 through water, but did not obtain those decisive results 

 which I sought. I then passed air through salts of lead, 

 obtaining results which have been already published some 

 years ; in these, however, the organic matter was not 

 estimated. When, however, the air was passed through a 

 highly coloured and highly oxidized body, such as per- 

 manganate of potash, the influence of the organic matter 

 became evident, and the relative condition of certain atmo- 

 spheres was estimated. 



By none of these methods, however, was the actual sub- 

 stance which has been so often sought really obtained. Its 

 indications were viewed telegraphically ; it was not handled 

 or seen in a separate state. I therefore exposed blood to 

 putrefaction, and caused air to bubble through it, obtain- 

 ing in this way a more concentrated but a similar action. 

 The air was then passed through a salt of lead as before. 

 This time chloride of lead was used : it was desirable to 

 use no organic acid, and no acid capable of oxidizing the 

 organic substances. Carbonic acid came over in great 

 abundance, and sulphuretted hydrogen. The sulphuretted 

 * From 'An Hypothetical Notion of the Plague,' by Mr. Place, 1721. 



