POISONS. 233 



there; but, on the whole, I do not think he can 

 fail to be satisfied with the wondeiTully 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 Avords, there is no poison in the above list 

 Avliich has the property, when applied to the Medus?e, 

 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 

 Medusa 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 neiwe-centre. 

 Again, in the second place, we must remember that 

 the method of administering the above-mentioned 

 poisons to the Medusae was very different from 



