NUTRITION. 393 



tremely minute granules and somewhat larger spherical particles of 

 insoluble matter. Only occasionally can a fragment of the disinte- 

 grated chloroplasts be seen. Apparently the fluid passmg the filter 

 contains practically nothing except the soluble and the amorphous, 

 colloidal constituents of the cell contents. If the grinding is thorough 

 enough the filtered fluid may contain all the contents of the cells, while 

 the sohds retained by the paper are seen to consist only of the walls 

 of the cells and the various ducts. 



Addition of alcohol equivalent to one-fifth of this filtered mixture 

 produces a bulky dark-green precipitate which separates, leaving a 

 green, slightly turbid solution. After separating this precipitate with 

 the centrifuge, the further addition of alcohol to one-third of the volume 

 of the original extract yields another large green precipitate and a 

 solution which can be easily filtered clear. On washing these green 

 precipitates with strong alcohol, chlorophyll and other substances are 

 easily removed, lea\dng an almost colorless residue. \^Tien this is 

 treated with ether a deep yellow extract is obtained which on evapora- 

 tion leaves a semi-solid, fatty residue. The precipitates thus washed 

 when air-dry are nearly colorless, friable products containing about 

 14 per cent of nitrogen, calculated ash-free. 



A considerable part of the first precipitate is not soluble at room 

 temperature either in an aqueous or in a 60 per cent alcoholic solution 

 containing 0.2 to 0.3 per cent sodium hydroxide, although such solu- 

 tions readily dissolve most types of proteins. If, however, the temper- 

 ature of such an alcoholic solution is raised to boiling, nearly all this 

 precipitate dissolves. When the resulting solution is neutralized 

 mth acid, most of the dissolved substance is precipitated and is then 

 readily soluble at room temperature in a very slight excess of either 

 acid or alkali. The second precipitate, which we call the "colloidal 

 protein" is almost completely soluble in cold, dilute aqueous alkalies. 



At least 40 per cent of the total spinach nitrogen belongs to this 

 colloidal protein, about one-third to substances which are soluble in 

 water, and a comparatively small part of the other fourth of the nitro- 

 gen belongs to chlorophyll, phosphatides, etc., soluble in strong alcohol, 

 and presumably a part of the remainder to nucleic acid. 



Since this colloidal protein is so readily precipitated by a relatively 

 small proportion of alcohol, while at the same time most of the chloro- 

 phyll, phosphatides, etc., which were pre\'iously insoluble in pure ether, 

 become soluble therein, it seems possible that within the cell these and 

 possibly other substances exist in chemical union as a complex which 

 forms a colloidal solution extremely sensitive to the action of alcohol. 

 If this is so, the solubility and other properties of the constituents of 

 this complex give no idea of their chemical or physical properties as 

 they are combined within the cell. 



