234 JELLY-FISU, STAR-FISH, AND SEA-URCHINS. 



that which we employ when administering them to 

 other animals ; for, in the case of the Medusie, the 

 neuro-muscular tissue is spread out in the form of 

 an exceedingly tenuous sheet, so that when the 

 animal is soaking in the poisoned water every por- 

 tion of the excitable tissue is equally exposed to its 

 influence ; and that the action of a poison is greatly 

 modified by such a difference in the mode of its 

 administration has been proved by Professor Gamgee, 

 who found that when a frog's muscle is allowed 

 to soak in a solution of vanadium, etc., it loses 

 its irritability, while this is not the case if the poison 

 is administered by means of the circulation. 



I may farther observe that in the case of all 

 poisons I have tried, the time required for recovery 

 after the animal is restored to normal water varies 

 immensely. The variations are chiefly determined 

 by the length of time during which the animal has 

 been exposed to the influence of the poison, but 

 also, in a lesser degree, by the strength of the solu- 

 tion enployed. To take, for instance, tlie case of 

 caffein or chloroform, if Sarsicie are transferred to 

 normal water after they first cease to move, a few 

 seconds are enough to restore their spontaneity; 

 wdiereas, if they are allowed to remain in the 

 poisoned water for an hour, they may not move 

 for one or two hours after their restoration to un- 

 poisoned water. In consequence of such great varia- 

 tions occurring from these causes, I was not able 

 to compare the action of one poison with that of 

 another in respect of the time required for effects 

 of poisoning to pass away. 



