390 PHYSIOLOGY. 



a stoppage of the spiracles has been observed, were either dead or upon 

 the point of death. But that the function of respiration may be long 

 interrupted in pupa, is attested by a number of experiments, and, 

 therefore, it is not at all improbable that the pupa may have exhibited 

 signs of life even when its spiracles were stopped up. 



The earliest physiologists, viz. Malpighi and Reaumur, instituted 

 experiments upon the effects of stopping the spiracles with oil or gum, 

 and obtained the result, that if the stoppage were long continued, it 

 would cause the death of the insect. More recently, Moldenhawer *, 

 in proof of his view that the spiracles were not the orifices of the 

 respiratory organs, made many experiments by stopping them with oil, 

 and the result obtained from his investigations was, that not merely 

 stopping the spiracles, but even merely brushing it over with oil, was fatal 

 to the insect system. But this is not the case. G. R. Treviranus f , 

 who repeated many of his experiments, observed death to ensue only 

 upon the stoppage of all its spiracles, and not when the body or portions 

 of it were brushed over with oil; and indeed upon the complete stoppage 

 of all the spiracles, it was some hours before death was produced. This 

 was the case with insects found under water. But the effects of the 

 stoppage were very various : caterpillars lived longest ; perfect insects 

 were sooner killed ; some, even upon a partial coating of oil, for instance, 

 a wasp, the breast and venter of which was covered with oil of almonds, 

 died in a few minutes. But as it is precisely upon the breast and 

 ventral portions that the orifices of the spiracles are placed, we may pre- 

 sume that they were stopped in this experiment. That it does not prove 

 fatal to cover some only of the spiracles, is proved by an experiment 

 upon a Meloe, the ventral spiracles of which were closed. Its preceding 

 activity remained almost unaltered, for the spiracles of the breast, which 

 Treviranus does not indeed know in insects, remained free, and through 

 these the beetle could breathe \. 



Whereas it has been observed upon the covering of some of the 

 spiracles only, namely, those lying upon the same segments, there 

 ensued a partial laming of that portion of the body thus deprived of 



* Beitrage zur Anatomic der Pflanzen, p. 309. 



t Biologic, vol. iv. p. 151. 



t Das organische Leben, p. 257. The majority of observations here made upon the 

 situation of the spiracles in the several orders is erroneous, as the description we have given 

 above will prove. 



