OP RESPIRATION, 387 



therefore, the rigid spiral filament which encircles all tracheae is 

 especially adapted to its constant distension, precisely as is the case 

 with the cartilaginous tracheae of the superior animals. Consequently, 

 by means of the elasticity of this filament, the trachea spontaneously 

 distends upon the distension of the abdomen, the compression of which 

 had decreased its compass ; and possibly it is as much distended beyond 

 its natural size, by the introduction of air upon inspiration, as it had 

 been previously contracted by the contraction of the abdomen, at least 

 Comparetti's experiments * upon locusts opened alive appear to indicate 

 as much, but it cannot be kept constantly contracted or distended 

 beyond its usual size owing to this filament. 



In general the respiratory motion is very unequal ; it is either 

 quicker or slower, according to the state of excitement or repose of the 

 entire system. It appears also to vary considerably in the several 

 orders. Sorg observed t in Lucanus Cervus from twenty to twenty-five 

 contractions in a minute, whereas in Locusta mridissima J there were 

 from fifty to fifty-five, and in Deilephila Euphorbia only twenty. 

 In a cockchafer, whose elytra I had cut half off, I could detect no 

 pulsation at all, even with the greatest attention, and by means o? a 

 lens, so long as it remained inactive and as it were asleep ; but upon 

 taking it into my hand, the warmth of which aroused it, pulsations 

 were to be seen, at first, it is true, very irregular, both in intensity and 

 the interval that elapsed between them, but it at last breathed regularly 

 when preparing for flight, and there were now about twenty-five 

 contractions in a minute ; but the abdomen after each contraction 

 gradually decreased, never subsequently distending so widely as at first, 

 but likewise it compressed itself more and more, so that there was an 

 equal ratio between the decrease of its dilatation and the increase of its 

 contraction. Shortly before taking flight it moved its whole body as it 

 were convulsively, the head was protruded and withdrawn, pro- and 

 mesothorax were also loosened from each other and again brought 



o o 



together, and, lastly, the valve of the cloaca was widely opened, and it 

 appeared to struggle during its violent respiration as if desirous of 

 disencumbering itself of an oppressive load. But all its endeavours 



* Obs. Anat. de Aura Interna comp. p. 290, according to Treviranus's Biologic, vol. 

 iv. p. 161. 



t Disquisit. Physiol. circa Respirat. Insectoram et Vermium, p. 27. 

 I Ibid. p. 46. Ibid. p. 66. 



c c 2 



