POISONS. 217 



120 per minute) together with a lessening of their 

 force. On sliglitly increasing the dose, the pulsa- 

 tions become languid, and prolonged pauses super- 

 vene. If the dose is again somewhat strengthened, 

 the pulsations become weaker and weaker, till they 

 eventually cease altogether. The animal, however, 

 is now in a condition of exalted reflex irritability ; 

 for its response to a single stimulus consists not 

 merely, as in the unpoisoned animal, of a single 

 spasm, but also, immediately after this, of a series 

 of convulsive movements somewhat resembling 

 swimming movements destitute of co-ordination. 

 If the strength of the solution be now again 

 increased, a stage of deeper ansesthesiation may be 

 produced, in which the Medusa will only respond 

 to each stimulation by a single spasm. In still 

 stronger solutions, the only response is a single 

 feeble contraction ; while in a nearly saturated 

 solution the animal does not respond at all. But 

 even from a saturated solution Tiaropsis diade- 

 mata will recover when transferred to unpoisoned 

 water. 



4. Strychnia. — The species of covered-eyed Medusa 

 which I shall choose for describing the action of 

 strychnia is C^'anasa capillata, which is most admir- 

 ably adapted for experiments with this and some 

 of the other alkaloid poisons, from the fact that in 

 water kept at a constant temperature its pulsa- 

 tions are as regular as are those of a heart. After 

 Cyana^a capillata has been allowed to soak for ten 

 minutes or so in a weak sea-water solution of 

 strychnia, unmistakable signs of irregularity in the 



