the luciferin-luciferase reaction really represents a catalytic oxidation of similar nature. As Dubois (1914 a) expresses it, we are dealing in luminous organisms with "1° une luminescence; 2° une chemiluminescence; 3° une oxyluminescence; 4° une zymoluminescence.
"Ou si l'on bien admettre que les zymases sont encore quelque chose de vivant, une Biozymoöxyluminescence." Perhaps it is not really necessary to admit that the enzymes are living in order that we may adequately visualize the nature of the photogenic process.
In the next chapter the properties of the three principal substances, luciferin, oxyluciferin and luciferase, will be studied more carefully.
CHAPTER VI
THE CHEMISTRY OF LIGHT PRODUCTION, PART II
Since Radziszewski's experiments on the oxidation of oils in alcoholic solutions of alkali, most of the early workers on Bioluminescence tacitly assumed that the oxidizable material was fat or a fat-like substance. Support was given to this view by the occurrence in cells of granules or globules from which the light was seen to come. We now know that these bodies are not fat droplets and that neither luciferin nor luciferase are soluble in such fat solvents as ether, chloroform, benzol or benzine. Phipson's description of the properties of noctilucin are too crude and inaccurate to be considered. Dubois did not study the chemical properties of luciferin and luciferase from Pyrophorus, the first form with which he worked, except to point out that Pyrophorus luciferase was destroyed on heating and was precipitated by alcohol while the Pyrophorus luciferin was not so affected. Luciferin was found only in the luminous organ of Pyrophorus, not in the blood; luciferase probably exists throughout the animal.[8]
[8] Private communication from R. Dubois.
Pholas luciferin.—In a series of papers since 1887 Dubois has studied the chemical properties of Pholas luciferin and Pholas luciferase. He finds the luciferin to be destroyed above 70° C., to dialyze slowly, to oxidize with light production in the presence of Pholas luciferase, KMnO4, H2O2, hæmatine and H2O2, BaO2, PbO2, hypochlorites, and the blood of various marine mollusks and crus
tacea. It is insoluble in fat solvents but forms a colloidal solution in water from which it is precipitated unchanged by picric acid, alcohol at 82°, and (NH4)2SO4. It is not precipitated by NaCl, MgSO4 or acetic and carbonic acids, except in presence of neutral salts. It forms an insoluble alkali albumin with NH4OH. Dubois (1887 a) stated at one time that it could be crystallized and has spoken of it as belonging to several different classes of substances, proteose, nucleoprotein, albumin. Most recently he describes luciferin as a natural albumin having acid properties. It occurs only in luminous, not in non-luminous animals, and is found in all parts of the mantle, especially the siphons. It does not occur in non-luminous parts of the mollusk. No photographs of luciferin crystals have ever been published.