Chap, in The construction of Protein 355 



and Fungi, but his results were negative. We must remem- 

 ber, however, that at first the search for formaldehyde was 

 similarly fruitless. 



The theory already alluded to that protein is constructed 

 in the plant from the more complex of the amido-bodies, 

 together with some form of sugar, has been advocated by 

 many observers since 1878, when the fact became known 

 that such amido-bodies are of frequent occurrence in leaves. 

 Borodin found in that year not only that they are formed 

 there, but that a great accumulation of them can be secured 

 by cutting off shoots and keeping them in the dark. Under 

 these conditions no sugar is formed and no protein is made. 



Pfeffer said in 1872 that asparagin is regenerated into 

 protein as starch is formed. We owe a good deal of 

 information on the occurrence of amino- and amido-com- 

 pounds in metabolism to the researches of E. Schulze and 

 his pupils since about that time. 



Many observations confirmatory of Borodin's were made 

 later by other botanists, but no one was able to throw 

 any light upon the mode of interaction of the two 

 groups concerned, nor has the way in which the sulphur 

 and phosphorus of protein are incorporated been discovered. 

 Contributions to our knowledge were made by A. Meyer 

 in 1885 and by Saposchnikoff ten years later, but neither 

 furnished proof of any of these points. Saposchnikoff 

 found that protein can be formed in isolated leaves in 

 the presence of light, particularly if they are supplied 

 with nutritive solutions containing combined nitrogen. 

 A diminution of the light retards the formation of carbo- 

 hydrates as we might expect, but it accelerates that of 

 protein. His experiments led him, however, no further 

 than the conclusion that protein is a secondary product 

 constructed from carbohydrates. 



We may now return to the relation of light to the pro- 

 cess. In 1888 Schimper put forward the view that the 



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