LIGHT BY LIVING ORGANISMS—McDERMOTT. 851 
generally, the presence of a reducing agent, and more particularly, 
probably of an unsaturated fatty-acid radical. 
Lund (#) has recently brought forth some evidence tending to show 
that in the photogenic process in the Lampyride, 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 (*) 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 (?) has studied the hydrolysis products of Noctiluca 
and finds a number of the ordinary physiologic amino acids. Lan- 
kester (°°) remarks that the products of metabolism in Noctluca 
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, hydrogen, 
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 (‘) also calls attention to the — of hydrogen peroxide on 
the fresh tissue. 
