. VIII. EFFECT OF CARBONIC ACID. 157 



insects were submitted, in the same way, to the influence 

 of cold. The tube being placed in ice, the light had not 

 ceased even at the end of fifteen or twenty minutes, though 

 it was more feeble, and not intermitting. When with- 

 drawn from the tube and placed on the hand, the animals 

 became as brilliant as ever. The same effect was obtained 

 with the posterior luminous segments. The tube contain- 

 ing the glow-worms and thermometer being placed in a 

 freezing mixture, whose temperature was 5 Reaumur [ = 

 20-75 Fahr.] the animals ceased to shine, and appeared 

 motionless in about eight or ten minutes ; but when they 

 were withdrawn and placed on the hand, life returned, and 

 with it light. If,' during the time they are in the tube at 

 5 Reaumur [ = 20-75 Fahr.] their segments be broken 

 by a pointed wire, a transient and very feeble light appears. 

 This fact is likewise confirmed by the observation that their 

 isolated posterior segments or luminous matter cease to 

 shine at this temperature. If the luminous matter thus 

 cooled be withdrawn and re-warmed, it recovers its billian- 

 cy for an instant, and the light before becoming extinct 

 acquires, as usual, a red colour when the heat has been too 

 strong. 



Effect of Carbonic Acid. I put, at the same time, into 

 two small equal-sized bell glasses ten glow-worms, and an 

 equal number of segments detached from other similar in- 

 sects. Then, after having filled the two glasses with mer- 

 cury, I introduced some carbonic acid. In a few minutes, 

 the light entirely disappeared, but without any remarkable 

 difference being observed between the segments and the 

 entire insects. When I introduced a little air, all reco- 

 vered their luminosity; and, by adding some bubbles of 

 oxygen, the effect took place more rapidly and brilliantly. 

 Glow-worms, which appeared dead in carbonic acid, re- 

 turned to life and motion on the introduction of oxygen. 



