=Insects.=--The author devoted considerable time, in the autumn of 1882, to observations on the effect of certain alkaloids on the common blow-fly, thinking it possible that the insect would exhibit a sufficient series of symptoms of physiological phenomena to enable it to be used by the toxicologist as a living reagent. If so, the cheapness and ubiquity of the tiny life during a considerable portion of the year would recommend it for the purpose. Provided two blow-flies are caught and placed beneath glass shades--the one poisoned, the other not--it is surprising what a variety of symptoms can, with a little practice, be distinguished. Nevertheless, the absence of pupils, and the want of respiratory and cardiac movements, are, in an experimental point of view, defects for which no amount or variety of merely muscular symptoms can compensate. From the nature of the case, we can only distinguish in the poisoned fly dulness or vivacity of movement, loss of power in walking on smooth surfaces, irritation of the integument, disorderly movements of the limbs, protrusion of the fleshy proboscis, and paralysis, whether of legs or wings. My experiments were chiefly made by smearing the extracts or neutral solutions of poisons on the head of the fly. In this way some of it is invariably taken into the system, partly by direct absorption, and partly by the insect’s efforts to free itself from the foreign substance, in which it uses its legs and proboscis. For the symptoms witnessed after the application of saponin, digitalin, and aconitine, the reader is referred to the articles on those substances. In poisoning by sausages, bad meat, curarine, and in obscure cases generally, in the present state of science, experiments on living animals are absolutely necessary. In this, and in this way only, in very many instances, can the expert prove the presence of zymotic, or show the absence of chemical poison. The Vivisection Act, however, effectually precludes the use of life-tests in England save in licensed institutions. Hence the “methods” of applying life-tests described in former editions will be omitted. § 29. =Effect of poisons on the heart of Cold-blooded Animals.=--The Vivisection Act does not, however, interfere with the use of certain living tests, such, for instance, as the testing of the action of poisons upon the recently extirpated hearts of cold-blooded animals. [Illustration: Williams’ Apparatus.]