A Russian naturalist has made a series of measurements, by a thermo-electric method, of the temperature of insects. A few of his results are noticed below. The temperature of the human body, it will be remembered, is essentially the same in the tropics and in the polar zones. Insects at rest have a temperature essen-, tially the same as that of the surrounding air in ordinary conditions of heat and of humidity. Under usual conditions the temperature of an insect rises with that of the surrounding air, only more slowly. When the air is very moist the insect's temperature may rise more rapidly than that of the air. When the insect begins to move, its temperature rises and continues to rise until the motion ceases. This rise of temperature continues till at about 38 deg. C. (102.2 deg. P.) a heat paralysis sets in. The paralysis is only temporary; it ceases as the temperature falls once more. Below 0.5 deg. C. (31 deg. P.) insects are perfectly without motion. The temperature must, in general, be raised to 12 deg. C. (53.6 deg. P.) before the wings are moved. For one species Saturnia pyri the highest temperature compatible with life is 115 deg. P. This is about the temperature that is fatal to vegetable life. For some time past prussic acid has been considered' to be the most deadly poison extant. Mr. Lascelles Scott, of Little Ilford, England, however, has now discovered a far more deadly poison the substance scientifically known as di-methylarsine cyanide, or more familiarly as cyanide of cacodyl. Three grains of this substance diffused in a room full of people would kill all present, so powerful is it. So deadly is this poison, that it is highly dangerous to handle it. It is a white powder melting at 33 deg. and boiling at 140 deg. When exposed to the air it emits a slight vapor, to inhale which is death. Mr. Lascelles Scott has experienced the deadly nature of this poison, for while he was assisting Sir B. W. Richardson in the compilation of his work "On the Causes of the Coagulation of the Blood," he tried its effect upon animals. One-millionth part of cyanide of cacodyl in the atmosphere of an airtight cage killed a dog almost instantaneously, and then its power was by no means exhausted, for a second, third, and fourth dog placed in the same cage, instantaneously die'd from the effect of that single infinitesimal dose. Although so little of the properties of this poison are known, it was first made many years ago. Cadet, the famous French chemist, by combining acetate of potassium with white arsenic, produced a fuming liquid which, although he did not know it, was oxide of cacodyl. The German chemist Bunsen combined this with cyanogen, a radical of prussic acid, and made cyanide of cacodyl, the formula of which is AsMe.Cy.
This article was originally published with the title "Science Notes" in SA Supplements 57, 1470supp, 191 (March 1904)