POISONS. 233 
there; but, on the whole, I do not think he can 
fail to be satisfied with the wonderfully close adher- 
ence which is shown by these elementary nervous 
tissues to the rules of toxicology that are followed 
by nervous tissues in general. In one respect, 
indeed, there is a conspicuous and uniform devia- 
tion from these rules; for we have seen that in the 
case of every poison mentioned more or less com- 
plete recovery takes place when the influence of the 
poison has been removed, even though this has 
acted to the extent of totally suspending irritability. 
In other words, there is no poison in the above list 
which has the property, when applied to the Meduse, 
of destroying life till long after it has destroyed 
all signs of irritability. What the cause of this 
uniform peculiarity may be is, of course, conjectural; 
but I may suggest two considerations which seem 
to me in some measure to mitigate the anomaly. 
In the first place, we must remember that in the 
Medusze there are no nervous centres of such vital 
importance to the organism that any temporary 
suspension of their functions is followed by im- 
mediate death. Therefore, in these animals, the 
various central nerve-poisons are at liberty, so to 
speak, to exert their full influence on all the ex- 
citable tissues without having the course of their 
action interrupted by premature death of the organ- 
ism, which in higher animals necessarily follows the 
early attack of the poison on a vital nerve-centre. 
Again, in the second place, we must remember that 
the method of administering the above-mentioned 
poisons to the Medusze was very different from 
