LIGHT BY LIVING ORGANISMS McDEEMOTT. 351 



generally, the presence of a reducing agent, and more particularly, 

 probably of an unsaturated fatty-acid radical. 



Lund ( 42 ) has recently brought forth some evidence tending to show 

 that in the photogenic process hi the LaHnryridse, there is an actual 

 using up of some material by oxidation, with the deposition of a 

 crystallin waste product in the tissues, forming to so-called urate or 

 reflecting layer, and states that it appears that there is present a 

 substance related to if not identical with some of the derivatives from 

 nucleic acids. His work is also strongly in support of the oxidation 

 hypothesis, or at least that the process requires the presence of oxy- 

 gen, even if it be not a simple oxidation. He suggests that the reduc- 

 tion of osmic acid may be due to the presence of a "reductase;" the 

 latter, however, might still be dependent on an unsaturated fatty- 

 acid radical for its activity. Coblentz ( 5a ) also* notes the expenditure 

 of the photogenic substance, without regeneration. 



All attempts to isolate and analyze the active substance have failed. 

 When the luminous organs of the firefly are treated with alcohol or 

 ether in an atmosphere of hydrogen, the liquid acquires a yellow 

 color, but no light emission occurs when it is exposed to the air or 

 treated with hydrogen peroxide. Lecithin does seem to exist in the 

 insect in small amount. 



Emmerling ( 20a ) has studied the hydrolysis products of Noctiluca 

 and finds a number of the ordinary physiologic amino acids. Lan- 

 kester ( 39a ) remarks that the products of metabolism in Noctiluca 

 are albuminoid and fatty granules. 



The interesting fact that the photogenic tissue of luminous life 

 forms preserves after desiccation the power to evolve light on the 

 application of water in the presence of air or oxygen, has long been 

 known, and it at once suggests other known instances of the preserva- 

 tion of biologic activity by drying, as exemplified by the yeasts and 

 ferments. By drying the photogenic tissue of Photinus pyralis over 

 sulphuric acid in hydrogen or a hydrogen vacuum, dry material has 

 been prepared which has retained its photogenic activity apparently 

 without loss when kept in sealed tubes for over 18 months. Indeed, 

 there seems to be no good reason why, under these circumstances, it 

 should deteriorate. In its conduct toward various chemical sub- 

 stances, the dried tissue, after moistening, does not differ essentially 

 from the live insect or the freshly detached luminous organ. It glows 

 on moistening in the air, somewhat brighter on moistening in oxygen, 

 and but dimly or not at all when moistened in nitrogen, lrydrogen, 

 and carbon dioxide. Moistened with 3 per cent hydrogen peroxide 

 instead of water, the dried tissue produces a much brighter light than 

 with water alone, accompanied by the decomposition of the peroxide. 



Lund ( 42 ) also calls attention to the effect of hydrogen peroxide on 

 the fresh tissue. 



