118 THE NATURE OF ANIMAL LIGHT 



Fe(0H)3, kaolin, talc and CaCog. It is not destroyed 

 by any of the enzyme solutions which I have tried. These 

 include such as are widely divergent in action: pepsin 

 HCl, trypsin, erepsin, salivary and malt diastase, yeast 

 invertase, urease, rennin and the enzymes of dried spleen, 

 kidney and liver substances. 



By extracting the dried Cypridinas ground to a pow- 

 der, the solubility of luciferin in non-aqueous solvents 

 could be easily studied, and by adding such reagents as 

 dilute acids, alkalies, neutral salts and the alkaloidal rea- 

 gents to an aqueous solution of luciferin the general bio- 

 chemical behavior of luciferin can be quite accurately 

 stated. For convenience the results of this study are 

 given in Table 8. 



Because the luciferin is almost completely precipitated 

 by saturation with (NH4)2S04, we may conclude that it 

 occurs, in water in the colloidal state. This excludes it 

 from belonging to one of the numerous groups of bio- 

 chemical compounds occurring in true solution and places 

 it among the known groups of colloidal substances, the 

 soaps, proteins, polysaccharides, phospholipins, galac- 

 tolipins (cerehrosides), tannins or saponins. It is not a 

 polysaccharide because nearly completely precipitated by 

 phosphotungstic acid, nor a soap because not precipitated 

 by calcium salts, nor a phospho- or galactolipin because 

 insoluble in benzine, hot or cold. It gives no tannin or 

 saponin tests. Only the protein group remains, and of 

 the eighteen protein classes recognized by the American 

 Society of Biochemists, the general properties of luci- 

 ferin indicate that it should be placed among the natural 

 proteoses, somewhere on the borderland between the pro- 

 teoses and peptones. The fact that luciferin will dialyze, 



