422 
ON THE APPLICATION OF PHYSIOLOGICAL TESTS 
chemical tests for it are peculiarly inadequate. 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, render them better adapted for this purpose than any 
other animals; and the objection ordinarily urged against their use, that the action of 
poisons on them is often different from that of the same substances on the higher ani¬ 
mals, 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 sto¬ 
mach, 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 ex¬ 
tracts was most decided and unmistakable. The effects produced were indeed very dif¬ 
ferent from those caused by digitaline; and we think that we have been able to dis- 
tinguish quite clearly between them. Still, the recognition of the fact that these ex¬ 
tracts 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 evi¬ 
dence. . 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 Staphysagria) 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. On the other hand, although this was not the primary object of our in¬ 
quiries, we may remark with reference to the frog-test for strychnia, that tetanic spasms 
were produced by none of the numerous substances with which we experimented, ex¬ 
cept veratrine and theine. It is of course well known that other agents, and notably 
some of die constituents of opium, produce tetanus in frogs; but on the whole our ex¬ 
periments lead us to hope that this test will hereafter be found of more value than is 
now generally supposed to be the case. 
We have devoted a considerable number of experiments to the solution of the prac¬ 
tical question, whether it be possible to obtain the characteristic effects of digitaline, not 
only from the extracts of liquids to which it had been artificially added, but also from 
extracts of the stomach-contents and vomited matters of dogs poisoned by that sub¬ 
stance. Ihe results of these experiments were perfectly satisfactory; and we think that 
our observations show conclusively that there is no difficulty in obtaining from these com¬ 
plex mixtures physiological effects identical with those of a pure solution of digitaline. 
Far more difficult to decide than the question of practical applicability, is the question 
as to the theoretical accuracy and conclusiveness of the physiological test for digitaline 
and the allied poisons, no this question we do not venture to give a positive answer. 
Our experiments justify, as we think, the hope that this test will be hereafter found of 
very considerable value in aiding in the detection of these substances; but it can be only 
by the combined labours of many observers, and not merely by one series of experi¬ 
ments, that this point can be finally settled. 
Ihe following are the conclusions at which we have arrived, and which are deduced 
from our own experiments in every instance, except where the contrary is expressly 
stated, under heading 2. 
A | ■ Digitaline is one of a small class of substances of which the action on frogs appears 
to oe identical. As the heart is the organ primarily affected by them, they may be 
called cardiac poisons, so far as frogs are concerned. 
_. These suostances are, besides digitaline, the Upas Antiar , the Helleborus viridis , 
and perhaps other species of Helleborus , the Tanghinia vcnenifera , the JDajaJcsch or 
arrow-pcnson of Borneo, the Carroval and Vao , South American arrow-poisons, and the 
Scilla maritima.. Of these we have ourselves experimented only with digitaline, antiar, 
th q Helleborus viridis and the II. niger, and the Scilla; and we believe that we are the 
first observers who have recognized the identity of the action on frogs of the last of these 
plants with that of the other substances placed in this group. Besides digitaline, only 
i w o of them, namely, the Helleborus and the Scilla , are likely to be the subject of medico¬ 
legal investigation m this country, and that but rarely. 
