LECT. VIII. MUTILATED INSECTS. 163 



water, and inverted over the hydro-pneumatic trough. In 

 twenty minutes, the insects ceased to glow ; but immedi- 

 ately after the introduction of some bubbles of air, they re- 

 turned to life, and again became luminous. I repeated this 

 several times, with the same insects. I repeated the expe- 

 riment with water, which I had previously boiled for two 

 hours. In this liquid, the insects evolved light during ten 

 or twelve minutes only. It is remarkable, that with other 

 liquids than those which act chemically upon the substance 

 of the insect, the duration of the phosphorescence should be 

 different. In alcohol and ether, the phosphorescence lasts 

 a little longer than in water ; in oil, on the contrary, its 

 duration is less. It is necessary to proceed in the way I 

 have here indicated, and not to confine oneself to placing 

 the insects in the liquid contained in a capsule. In each 

 of these last experiments, I believe that the duration of the 

 phosphoresence ought to be, in part, attributed to the air, 

 which always remains adherent to the insect. 



I tried another experiment, which, I think, I ought to 

 describe to you, before deducing from the preceding, their 

 necessary consequences. I separated the segments of se- 

 veral very lively glow-worms, and then crushed and rubbed 

 them in a small agate mortar. By treating them thus, the 

 matter of the segments at first appeared very luminous ; but 

 after a few seconds, the phosphorescence diminished, and 

 then entirely ceased. This result was accelerated, when 

 the mortar was moderately warmed. I placed at the bot- 

 tom of a bell-glass, one portion of the triturated substance 

 of the segments, and at the moment when it ceased to shine, 

 I filled the glass with mercury, inverted it over the trough, 

 and introduced oxygen. On contact with this gas, I saw 

 once, and only once, amidst numerous experiments which 

 I made, a very faint light, but which ceased in an instant. 

 In another experiment, in which the triturated matter also 



