THE CHEMISTRY OF LIGHT PRODUCTION 121 



solubility in alcohols, acetone, esters, etc., and non-diges- 

 tibility by trypsin or erepsin, which have almost universal 

 proteolytic power. 



The best known class of proteins soluble in alcohol is 

 the prolamines of plants, but the prolamines are insoluble 

 in water and in absolute alcohol. Zein, the prolamine of 

 coni, is soluble in 90 per cent, ethyl, methyl, and propyl 

 alcohols, in glycerol heated to 150° C, and in glacial acetic 

 acid. Recently Osborne and Wakeman (1918) have de- 

 scribed a protein from milk having solubilities similar 

 to those of gliadin, the prolamine of wheat. Welker 

 (1912) has described a substance, obtained from Witte's 

 peptone, giving the biuret, Millon, and Hopkins-Cole tests, 

 which is soluble in water and absolute alcohol but not in 

 ether, and it is possible that others of the peptones are 

 soluble in absolute alcohol. On the other hand, some 

 proteins in the absence of salts form colloidal solutions 

 in strong alcohol from which they may be precipitated by 

 an appropriate salt. As the absolute alcohol extract of 

 Cypridince was made from dry material containing the 

 salts of sea water, some salt was present, but there is 

 always the possibility of sol formation. 



If we extract dried Cypridince, which have previously 

 been thoroughly extracted with benzine or ether, with 

 800 c.c. of boiling absolute alcohol for an hour, filter 

 the alcohol extract through blotting paper and hardened 

 filter paper, quickly evaporate the filtrate to dr^mess 

 on the water bath, and dissolve the residue in a small 

 quantity of water saturated with COo,* we obtain a 

 yellow opalescent solution which gives a bright light 

 with luciferase. This solution contains some protein 



• To make the solution slightly acid and prevent oxidation of the 

 luciferin. 



