The Birmingham age-herald., 1911-06-25
HOW FREELY
 MAKES LIGHT
Insect Is Living Lamp and Produces
 Flame by Oxidation

From the American Naturalist
 That the fiiref1ies are lamps not only in the sense that they give light, but also in that they produce this light by oxidation, that Is by practical combus- tion, albeit very slow, seems to be proved by investigations by practical combus- ton, albeit very slow, seems to be proved by investigation by F. Alexander Me Dermott and Charles G. Crane. of the Hygienic Laboratory of the United States Public Health and Hospital Service in Washington. The authors note that all though there are about 25 species of these insects in the United States, little work has been done in the microscopical study of their light-producing organs The au- thors find that these organs are traversed by tubes continuous with those used for breathing and that there is every evil dence that air is drawn into the organs by the insect to produce light by oxida- ton. Three species altogether were ex- amined. In all the lumious organ is divided into two distinct layers, the inner one being white and opaque, and serving as reflector. and the outer being vel Jewish and translucent, and containing the actual light-producing mechanism The luminous organs are penetrated from the' interior of the insect outward by innumerable tubes, which ramifs within the true luminous tissue, running diagonally outward and finally uniting with the breathing tubes or windppes with which they are apparently identical We read.
 'The entire system suggests that the air is drawn in through the breathing tracheae and forced through the fine passages in the true photogenic tissue. where the oxygen of the air is consumed in biologic oxidation. In the sections of pyrais there are clearly seen bundles of muscle f1bers on either side of the cen- ter line of the insect, which pass com .pletely through the abdomen, almost yer tically, and are attached to the exterior chitin at the top and bottom. At about the same point other muscle fibers pass inward from the point of maximum width at each side; these fibers have not been traced to their full extent, but they ap- pear to pass upward and toward the cen ter near the dorsal side of the insect.
 Tt may be well here to call attention to certain differences between photuris and photinus. as shown by the cross sections of the insects, While the thick ness of the refecting layer is about the same in both species, the layer of true photogenic tissue Is much thinner both actually and in comparison with the re- hecting layer. in photuris than in pho tinus: this difference is clearly seen. This
 
 when considered in connection with the slight differences in the quality of the emitted light, and in the modes of emis- sion of the two species.
 That the photogenic process Is an oXl- dation is scarcely to be doubted, in view of the work which has been done al ready.
 Tt seems possible that the rehectng layer fulfills a twofold purpose-that of refecting the light outward and thus in- creasing it's intensity In the desired direc- tion, and of protecting the insect itself from it's own radiations. It has recently been shown by Coblentz that the pyralis and other Lampyridae contain a fluores- cent material, and a number of observers have shown that fluorescent materials injected into a living animal show a higher degree Of toxicity when the ami nal subsequently is exposed to light than if it be left in the dark.