380 LOUIS PASTEUR 



this effect as general. It would be perfectly logical to ex- 

 tend the results of which we are speaking to all plants, and 

 to believe that the proteic matter of vegetables, and per- 

 haps of animals also, is formed exclusively by the activity 

 of the cells operating upon the ammoniacal and other 

 mineral salts of the sap or plasma of the blood, and the 

 carbo-hydrates, the formation of which, in the case of the 

 higher plants, requires only the concurrence of the chemical 

 impulse of green light. 



Viewed in this manner, the formation of the proteic 

 substances, would be independent of the great act of re- 

 duction of carbonic acid gas under the influence of light. 

 These substances would not be built up from the elements 

 of water, ammonia, and carbonic acid gas, after the decom- 

 position of this last; they would be formed where they are 

 found in the cells themselves, by some process of union 

 between the carbo-hydrates imported by the sap, and the 

 phosphates of potassium and magnesium and salts of am- 

 monia. Lastly, in vegetable growth, by means of a carbo- 

 hydrate and a mineral medium, since the carbo-hydrate is 

 capable of many variations, and it would be difficult to 

 understand how it could be split up into its elements before 

 serving to constitute the proteic substances, and even cel- 

 lulose substances, as these are carbo-hydrates. We have 

 commenced certain studies in this direction. 



If solar radiation is indispensable to the decomposition 

 of carbonic acid and the building up of the primary sub- 

 stances in the case of higher vegetable life, it is still pos- 

 sible that certain inferior organisms may do without it and 

 nevertheless yield the most complex substances, fatty or 

 carbo-hydrate, such as cellulose, various organic acids, and 

 proteic matter; not, however, by borrowing their carbon 

 from the carbonic acid which is saturated with oxygen, but 

 from other matters still capable of acquiring oxygen, and 

 so of yielding heat in the process, such as alcohol and acetic 

 acid, for example, to cite merely carbon compounds most 

 removed from organization. As these last compounds, and 

 a host of others equally adapted to serve as the carbon- 

 aceous food of mycoderms and the mucedines, may be pro- 

 duced synthetically by means of carbon and the vapour of 



