OF RESPIRATION. 391 



air, Reaumur and Bonnet * among the earlier naturalists, and 

 Treviranus among the modems, have made experiments upon this 

 point. According to Bonnet, the oil inserts itself within the spiracle, 

 and by that means still more impedes respiration. Treviranus, who 

 stopped only the posterior spiracles of the caterpillar of Cossus Ugniperda 

 with oil, observed a trembling^ and raising of the last abdominal 

 segment, but which, however, soon disappeared, after which the cater- 

 pillar exhibited no further morbid symptom. The same was the case 

 with a green locust, the thoracic spiracles of which were stopped with 

 oil : at first the legs appeared to become weaker and motionless, but it 

 subsequently recovered. My opinion is that this phenomenon of a 

 partial laming can present itself only immediately after the closing of 

 the spiracle, for subsequently air will pass from other spiracles into 

 those tracheae whose orifices have been closed, particularly as all the 

 tracheae stand in immediate connexion together, at least in the majority 

 of insects. It is only so long as the organisation is deprived of this 

 auxiliary assistance, that symptoms of lameness can appear. But even 

 without this assistance, it is scarcely advisable to seek in animals which 

 stand only upon a central grade of organisation for the uniform pheno- 

 mena observable in the more regulated conditions of life of the superior 

 animals. How long a time cannot insects pass beneath water or in 

 spirits of wine without respiring, and yet recover from their stupor ! 

 In the latter they indeed speedily die, but I know many instances of 

 beetles having been immersed in spirits of wine for twelve hours, and, 

 upon being removed from it, recover all their functions. But it is 

 much more fatal for insects to inspire air impregnated with the fumes 

 of evaporated spirits of wine ; it is true that here they die more slowly, 

 but at the latest in the course of half an hour, and when once thoroughly 

 made torpid, they do not again recover. 



230. 



The mechanism of respiration in insects which live in water is not 

 in general diiferent from that of those which live constantly in the air. 

 But this observation refers especially to those only which breathe even 

 in this medium through spiracles, whereas the process in those which 

 breathe through gills is somewhat different. 



Those water insects which breathe through spiracles must come to 



* Contemplations de la Nature, t. ii. 



