1865.] for certain Organic Poisons. 271 



substance believed to contain the poison on the animal experimented on 

 be identical with the known effects of that poison upon the same animal, 

 and that these effects be capable of being produced by no other agent or, 

 at any rate, only by a limited number of other agents. 



In this spirit we have conducted a series of investigations, with reference 

 to the detection of digitaline and of certain allied substances. We selected 

 that poison, not only because of the interest which attaches to it at the 

 present time, but also because the chemical tests for it are peculiarly in- 

 adequate. The animals which we employed in all our experiments were 

 frogs. Their sensibility to small quantities of poison, the fact that they 

 are but little liable to be affected by fear or other accidental circumstances, 

 and the independence of their organs, which makes it possible to determine 

 with accuracy the nature of the effects produced, have rendered them better 

 adapted for this purpose than any other animals ; and the objection ordi- 

 narily urged against their use, that the action of poisons on them is often 

 different from that of the same substances on the higher animals, has no 

 validity when the question of physiological evidence is looked at from our 

 point of view. 



It has been expressly denied, by those who have advocated the use of 

 physiological tests, that animal extracts, such as those obtained from the 

 contents of the human stomach, or from vomited fluids, could in themselves 

 be poisonous to the lower animals. We thought it desirable, however, to 

 make some direct experiments upon this point; and, to our surprise, we found 

 that in almost every instance the toxic action of such extracts was most 

 decided and unmistakeable. The effects produced were indeed very dif- 

 ferent from those caused by digitaline ; and we think that we have been 

 able to distinguish quite clearly between them. Still, the recognition of 

 the fact that these extracts exert a poisonous action, independently of the 

 presence of any of the ordinary toxic agents, must have an important 

 bearing upon the application of physiological evidence. Unless some 

 points of difference should hereafter be discovered, it will render impossible 

 the detection of many vegetable substances (among which we may mention 

 lobelia, emetina, veratrum viride, and delphinium staphisagria) by their 

 physiological effects. And it makes invalid (at least so far as frogs are 

 concerned) all evidence of this kind, in which the state of the heart is not 

 more particularly described than has hitherto been the case, so far as 

 the frog-test for strychnia is concerned ; on the other hand, though this 

 was not the primary object of our inquiries, we may remark that tetanic 

 spasms were produced by none of the numerous substances with which we 

 experimented, except veratrine and theine. It is of course well known 

 that other agents, and notably some of the constituents of opium, produce 

 tetanus in frogs ; but on the whole our experiments lead us to hope that 

 this test will hereafter be found of more value than is now generally sup- 

 posed to be the case. 



We have devoted a considerable number of experiments to the solution 



