LECT. VIII. INFLUENCE OF POISONS. 169 



In this condition, we may strongly irritate the thorax of the 

 insect without succeeding in producing phosphorescence. 

 In order that this effect should take place, it is necessary 

 to touch the luminous segments themselves; the irritated 

 points then glow, and the light thus produced, goes on ex- 

 tending itself over the untouched portion of the segments. 

 If we perform this experiment by putting the insect upon 

 the stage of the microscope, we can judge still better of the 

 production and diffusion of the light. In order to succeed 

 in this experiment, it should be made in the dark, and no 

 light should be allowed to fall on the object. We perceive 

 an extremely rapid oscillatory movement in the parts of the 

 phosphorescent matter, and at the same time they become 

 luminous. 



Influence of Poisons. I have frequently tried the effect 

 of nux vomica and opium, on the phosphorescence of these 

 insects. For example, I dissolved 0-265 gramme of the 

 extract of opium, or of the alcoholic extract of nux vomica, 

 in 61 grammes of water, and placed the glow-worms in 

 bell-glasses, filled with solutions thus prepared, and inverted 

 over similar liquids. By proceeding thus, there was no 

 contact with air. The results of a great number of ex- 

 periments induce me to conclude, that the insects die, in 

 the solution of nux vomica, eight or ten minutes sooner 

 than they would in water. On the contrary, in the solution 

 of opium, the phosphorescence continues eight or ten 

 minutes longer than in water. I hope to be able to return 

 to this object of our study, which I have now only glanced 

 at, and which requires a greater number of experiments. 



I will add, that those glow-worms which had ceased to 

 shine in water, shone anew on contact with the air; whilst 

 those which had been submitted to the action of nux vomica, 

 or of opium, shone no more and died. Hence, the action 



