CHAP, v The Discovery of Chetnosynthesis 369 



he employed a culture fluid containing nothing but inorganic 

 compounds, the most suitable being ammonium sulphate, 

 common salt, and magnesium carbonate. Hueppe made a 

 similar observation in 1887. 



The work of Heraeus and of Hueppe formed the starting- 

 point of the discovery. It was carried much further by the 

 researches of Winogradsky, who cultivated the organisms 

 with great care in various media, both Liquid and solid. 

 Using the former he found they flourished in a solution 

 containing ammonium sulphate, potassium phosphate, and 

 basic magnesium carbonate. He obtained better results 

 when he used as a basis a preparation of gelatinous silica 

 with which he incorporated a sterilized solution of the 

 sulphates of ammonium, magnesium, and potassium, with 

 some carbonate of sodium. The necessity for the presence 

 of the carbonate was due to the formation of the nitrous 

 and nitric acids by the microbes ; this he found was met 

 in the soil by the presence of calcium carbonate. 



Winogradsky succeeded in cultivating the organisms on 

 another solid medium containing mineral compounds in 

 a basis of 1-5 per cent, of agar-agar. 



In such media the organisms increased with great rapidity, 

 such multiplication involving, of course, a manufacture of 

 organic substance from the inorganic materials supplied to 

 them. Like his predecessors, Winogradsky found that they 

 were injured by the presence of organic nutrients of even 

 so lowly a form as potassium tartrate. In the absence of 

 all such organic substances the growth was so great that 

 he could estimate the formation of organic material quanti- 

 tatively. 



It was clear that the gain of carbon which his cultures 

 showed could only have taken place at the expense of the 

 carbonates of the nutritive media, or of the carbon dioxide 

 of the air. His quantitative analyses showed that the latter 

 certainly contributed to the process, which, as we have 



GREEN A a 



