394 CARNEGIE INSTITUTION OF WASHINGTON. 



The residue of the cell-walls, etc., contained about 16 per cent of the 

 total nitrogen of the leaves. Evidence was obtained that most of the 

 nitrogen in this residue of the cell- walls, etc., belonged to constituents 

 of unruptured cells, or of those from which the contents had not been 

 completely removed, and was consequently protein nitrogen. As a 

 result of this investigation it was found that about one-fourth of the 

 solids of the spinach leaf is protein and that one-fourth of its total 

 nitrogen belongs to non-protein substances soluble in water. 



The dry solids of the spinach leaf are much richer in protein than 

 are any of the cereals, or, in fact, some of the commercial protein con- 

 centrates, such as bran, middlings, etc. If we remember that the cells 

 of leaves are physiologically among the most active that we know, 

 it should not surprise us to discover that the chemical constitution of 

 their contents is much like that of the cells of active animal tissues. 



Since many green foods, such as alfalfa or clover, consist chiefly of 

 leaves and when dried and cured are fed as hay, it seemed desirable 

 to examine the spinach leaves after they had been dried in a current 

 of warm air below 60 and to compare the results obtained with those 

 yielded by the green fresh leaves. 



The proportion of substances soluble in water is a little greater in 

 the dried leaf than in the green, both protein and non-protein sub- 

 stances contributing to this small excess. The distinctly greater 

 amount of proteose found in the extract of the dried leaf compared with 

 the fresh indicates a slight autolysis during drying, but proof that such 

 a change actually occurs can be secured only by comparing the results 

 obtained with parts of the same sample. 



The percentage of the non-protein organic substances extracted 

 from the dried leaves with water is the same as that remaining in 

 solution after precipitating the turbid extract of the green leaves 

 by the addition of one- third volume of alcohol. In both cases the 

 percentage of the total nitrogen soluble in water also is the same. 

 The amount of the colloidal protein obtained from these two sources 

 was likewise nearly the same; hence the results of this comparison 

 justify the conclusion that data obtained with leaves carefully dried 

 at a low temperature closely represent the composition of the leaf in 

 its fresh green condition. 



Dilute alcohol precipitates 43.5 per cent of the spinach nitrogen 

 from the colloidal solution obtained by grinding the fresh leaves 

 with water, and most of this is protein nitrogen. The residue of cell- 

 walls, etc., still contained nitrogen equal to 15.2 per cent of the total 

 nitrogen of the leaf, which for the most part is almost certainly protein 

 nitrogen. As there is good reason to believe that most of this belongs 

 to proteins of the same character as those found in the extract, we shall 

 not go far wTong in assuming that in the fresh leaves at least 58 per cent 



