NUTRITION. 



395 



of the spinach nitrogen, or 21.2 per cent of the spinach soHds, belongs 

 to this protein. 



The protein extracted from the dried leaves by alkahne alcohol, 

 and which is unquestionably the same as that precipitated from the 

 aqueous extracts of the fresh leaves by the addition of alcohol, con- 

 tained a little smaller proportion of the total spinach nitrogen than 

 did the colloidal protein obtained from the water extract of the fresh 

 leaves, but this deficit was made up by a correspondingly larger pro- 

 portion of water-soluble proteins, possibly formed by autolysis during 

 drying. 



We have not taken into account its possible contamination with 

 insoluble non-protein nitrogenous compounds. Doubtless the nuclei 

 of the cells contain nucleic acid, but either the amount of this is so 

 small, or else its properties are so different from the nucleic acids with 

 which we have been familiar, as to yield negative results with such 

 tests as were employed. Assuming that the undetected non-protein 

 nitrogenous substances contain too small a proportion of the spinach 

 nitrogen to have importance for this preliminary investigation, we 

 can state the proportion of the spinach nitrogen among the various 

 groups as given below: 



Stated in terms of percentage of the dry solids of the spinach leaf, 

 the proportions of the different proteins (NX 6.25) obtained from the 

 fresh and dry leaves respectively were as follows : 



