THE CATALASE CONTENT OF LUMINOUS AND NON-LUMINOUS INSECTS COMPARED1 ACCORDING to Dubois2 and others the production of light by luminous organisms is an oxidative process. If this is true then it would seem that oxidation should be correspondingly more intense in luminous insects than in non-luminous insects. It has been shown that the catalase content of the different muscles of animals is proportional to the amount of oxidation in these muscles and that the catalase is increased or decreased under the same conditions under which oxidation is increased or decreased. This and

similar evidence would seem to indicate a close relationship between the catalase content of a tissue and the amount of oxidation in that tissue If oxidation is more intense in luminous than in non-luminous insects then the catalase content per unit of weight of luminous insects should be greater than that of non-luminous insects. The object of this investigation was to determine if the catalase content per unit of weight is greater in a luminous insect, such as the firefly (Photinus), than it is in non-luminous insects, such as moths, butterflies, honey-bees and bumblebees.

Method.-After the insect was weighed it was ground up with sand in a mortar. This ground material was added to 50 c.c. of hydrogen peroxide in a bottle and as the oxygen gas was liberated from the hydrogen peroxide by the catalase it was conducted through a rubber tube into an inverted burette previously filled with water. In this way the amount of oxygen liberated in ten minutes from 50 c.c. of hydrogen peroxide was collected. The volume of oxygen was read off directly from the burette, where it had displaced the water. After this volume had been reduced to standard atmospheric pressure the resulting volume

1 From the Physiological Laboratory of the University of Illinois. From experiments carried out at Nela Research Laboratory.

was taken as a measure of the catalase content of the insect. Knowing the weight of the insect, the amount of catalase per 30 milligrammes of material was calculated. The calculation was made on the basis of 30 milligrammes of material, because it was found that three of the fireflies used weighed approximately 30 milligrammes. The hydrogen peroxide was prepared by diluting commercial hydrogen peroxide with an equal volume of distilled water. A full description of the method may be found in a previous publication.

Experiments.-Three fireflies previously ground up in a mortar with sand were introduced into a bottle containing 50 c.c. of hydrogen peroxide and the amount of oxygen liberated in 10 minutes was determined. Ten such determinations were made with an average of 118 c.c. of oxygen per 30 milligrammes of firefly. Similarly a moth ground up in sand was introduced into 50 c.c. of hydrogen peroxide and the amount of oxygen liberated determined. The average amount of oxygen liberated by moths was 8 c.c. of oxygen per 30 milligrammes of material. Determinations were also made using honey-bees, bumble-bees, and butterflies. The amount of oxygen liberated in none of these determinations exceeded 25 c.c. of oxygen per 30 milligrams of material. "

Conclusions.-The catalase content of a luminous insect where oxidation is presumably more intense is greater than that of a nonluminous insect where oxidation is less intense.

UNIVERSITY OF ILLINOIS

W. E. BURGE

EFFECT OF SMELTER GASES ON INSECTS1 Ir is often claimed that the waste gases, particularly sulphur dioxide, thrown off during the process of smelting copper, lead and some other ores, have a very decided influence on the number of insects in the vicinity of the smelters. Some believe that few if any

1 Contribution from the laboratories of the American Smelting and Refining Co., department of agricultural investigations.

insects can live in such regions because of the baneful effect of the gases, others believe that insects are unusually abundant there, particularly in regions where more or less injury has been done to vegetation under conditions that formerly existed in some of the smelters. Bees are thought to be particularly susceptible to these gases and it is often claimed that their numbers are so reduced in smelter regions as to seriously affect the fruit crops because the flowers are not properly fertilized. There is no basis whatever for any such claims or beliefs. For several years I have spent all or part of each summer in studying the insects in regions where smelters are located and, for purposes of comparison, in similar adjacent regions, and in no instance have I been able to detect any differences in the number of insects or in the extent of insect injury, due to the presence of smelter gases.

During the last three years the Department of Agricultural investigations of the American Smelting & Refining Co. has carried on extensive series of experiments to test the effect of sulphur dioxide on various kinds of vegetation. As insects are often covered over by the cabinets when they are placed over the plots of grain or other vegetation for fumigating, I have had many opportunities to watch their behavior when subjected to known quantities of sulphur dioxide.

The cabinets used in these experiments were about six feet square and five feet high and were made of celluloid with a light framework of wood. Through these cabinets a current of air carrying a known quantity of sulphur dioxide was driven by means of electric fans. Every precaution was taken to see that the concentration of the gas was constant in all parts of the cabinet throughout the experiment. The time of fumigation varied from half an hour to two or three hours. In every experiment a check cabinet where conditions were exactly similar, except for the absence of the sulphur dioxide, was used. The following sets of definite experiments and observations were made in 1916.

A number of honey bees were placed in a cabinet where SO, was being introduced, the

strength being 1 part of SO, to 1 million parts of air. During the half hour that they were submitted to the fumigation the bees behaved in the same way as did other bees placed in the check cabinet where no gas was being introduced.

In another experiment bees, butterflies, grasshoppers and mosquitoes were placed in the cabinet where 5 parts of SO, to 1 million parts of air was being introduced. The experiment was continued for one hour during which time the insects behaved in a normal way, some of the grasshoppers feeding during much of the time as contentedly as they would have fed outside of the cabinet. When the cabinet was removed the insects flew or hopped away and none showed any ill effects due to the confinement for one hour in this concentration of the gas.

At another time while fumigating some alfalfa plants with a very high percentage of SO2, 25 parts of the gas to 1 million parts of air, I watched a number of insects that were on the plants in the cabinet. The alfalfa weevils, adults and larvæ, went on with their work undisturbed. Flies, mosquitoes, leafhoppers, grasshoppers and ladybird beetles, behaved in a perfectly normal way and at the end of the hour over which the experiment extended, it could not be seen that the fumigation had had any effect on them.

As the concentration of gas in the last experiment was several times as high as we should ever find in the field even quite near the smelters, it is safe to say that the sulphur dioxide given off by the smelters has no effect whatever on the insects in that region.

It is true that SO, generated by burning sulphur in a room or other enclosed spaces is sometimes recommended for killing insects. But this is used at the rate of 2 lbs. of sulphur for every 1,000 cubic ft. of space. At sea level and at 20° C. or 68° F. this would give a concentration of gas equal to 24,009 parts of gas to one million parts of air. Even at this rate with prolonged fumigations the insects are not always all killed!

STANFORD UNIVERSITY

R. W. DOANE

would deny the validity of this assumption, let us consider the typical compounds of old-fashioned organic chemistry in regard to whose molecular structure we already know much-at the very least we may speak definitely of the relative positions of the atoms within their molecules. Among such compounds we find the striking phenomenon of isomerism. Numerous isomers, substances of precisely the same chemical constituents and differing only in the relative order in which the atoms are placed in the molecule, have been prepared. In the case of complex substances, if it were worth while, millions of such isomers could be prepared. Yet these isomers will keep for years, and probably would for centuries, without changing into one another. In these inert organic compounds the atoms are so persistently retained in definite positions in the molecule that in one part of the molecule atoms may be substituted for other atoms and groups for groups, sometimes through reactions of great violence, without disturbing the arrangement of the atoms in some other part of the molecule. It seems inconceivable that electrons which have any part in determining the structure of such a molecule could possess proper motion, whether or

bital or chaotic, of any appreciable ampli

tude. We must assume rather that these

electrons are held in the atom in fixed equilibrium positions, about which they may experience minute oscillations under the influence of high temperature or electric discharge, but from which they can not depart very far without altering the structure of any molecule in which the atom is held.

Let us therefore consider whether the physicists on their part offer any irrefutable arguments in favor of an atomic model of the type of Bohr's. In an atom of the simplest type, composed of a single positive particle and a single electron, if

these fail to merge with one another until their centers are coincident—and it is universally assumed that they do not so merge

only two explanations are possible: either the ordinary law of attraction between unlike charges (Coulomb's law) ceases to be valid at very small distances, or the electron must be in sufficiently rapid motion about the atom to offset the force of electric attraction. The first of these explanations is the one which I have adopted. The second, which has been adopted largely because it appears to save Coulomb's law, is the one which has led to Bohr's atomic model, in which the electron revolves in definite orbits about the central positive particle. Now it has frequently been pointed out, and indeed it was well recognized by Bohr himself, that this model is not consistent with the established principles of the electromagnetic theory, since in the classical theory a charged particle subjected to any kind of acceleration must radiate energy, while, according to the Bohr hypothesis, radiation occurs only when an electron falls from one stable orbit into another. Since, however, the equation for electromagnetic radiation is one of the more abstruse and less immediate deductions of the classical theory, it might

be possible by slight modifications of the

fundamental electromagnetic equations to reconcile them with the non-radiation of

the orbital electron. I wish therefore to

point out a far more fundamental objection to the theory of the revolving electron, due to the fact that Bohr has been forced to assume that this revolution must continue even down to the absolute zero of temperature."

If, in Fig. 1, the circle represents the orbit of an electron B revolving about the positive center A, and if C represents a charged particle in the neighborhood, then if the electron exerts any influence what

4.

FIG. 1.

B

soever upon the particle C, the latter will be set into sympathetic motion, and a part of the energy of the atom at the absolute zero will be contributed to the particle C, contrary to the most fundamental principles of thermodynamics. Therefore, unless we are willing, under the onslaught of quantum theories, to throw overboard all of the basic principles of physical science, we must conclude that the electron in the Bohr atom not only ceases to obey Coulomb's law, but exerts no influence whatsoever upon another charged particle at any distance. Yet it is on the basis of Coulomb's law that the equations of Bohr were derived.

In spite of this and other similar serious objections to Bohr's atomic model, I should not wish to minimize the importance of his work. He has been the first to present any sort of acceptable picture of the mechanism by which spectral series are produced, and especially he has traced a relation between two important constants of nature, Rydberg's fundamental frequency, and the Planck constant h which plays so important a part in modern physical theory. I should therefore be loath to suggest an abandonment of the extremely interesting leads which Bohr's theory has suggested, nor do I think this necessary,

2 It will be noted that this objection applies with equal force to the Planck oscillator which maintains energy even at the absolute zero.

for I believe that relationships similar to those obtained in Bohr's theory may be obtained, even if we substitute for the orbital atom of Bohr a static atom, and, moreover, I believe that by making this substitution we may not only obtain a model of the atom which is consistent with known chemical facts, but also one which does not require the abandonment of the principal laws of mechanics and electromagnetics. I should state at once, however, that I do not claim for the atomic model, which I am about to sketch in rough outline, the same finality that I would claim, for example, for the molecular model of methane which I have previously offered. It is rather a suggestion of the direction in which we may work towards the solution of a problem of extraordinary difficulty with the most hope of ultimate success. It is evident to any one familiar with the extreme complexity of the spectra of some substances that many years must elapse before anything approaching to a final explanation of such baffling phenomena can be expected. All we can do at present is to suggest certain directions of investigation which may lead ultimately towards the desired end. With this understanding, you will not consider it too presumptuous if I start by discussing not the structure of the complicated system that we call the atom, but rather the structure of the electron itself, or, if you prefer, the structure of the field of force about the electron.

If we postulate, at small distances, the nonvalidity of Coulomb's law of force between the centers of two charged particles, we are doing nothing that is really new. In the older conception of the electron as a charged sphere of definite radius, the sphere being itself held together 3 I refer here and elsewhere to my paper "The Atom and the Molecule," J. Am. Chem. Soc., 38: 762, 1916. See also Proc. Nat. Acad., 2: 586,

1916.