428 PHYSIOLOGY. 



parts ; and now, as the first stands upon a very low grade in insects, 

 and the second is wholly deficient, consequently a cicatrisation of 

 wounds can never be effected. But if beneath the wounded skin a 

 new one is formed it uninterruptedly covers the wound of the old one, 

 and after moulting the larva appears healed, if the wound be not of a 

 description to affect its life, and thus interrupt all future changes of 

 the skin. 



253. 



In our representation of the metamorphosis we have omitted one 

 phenomenon which was mentioned in earlier parts of the work ( 114 

 127), namely, the simultaneous moulting of the intestinal canal and 

 tracheae, with that of the external integument. Bonnet * and Swam- 

 merdamm f, the first physiologists of their age, especially with respect 

 to the class of insects, maintained this opinion, and from their works 

 it has passed into those of modern physiologists ; whereas Herold, in 

 his history of the development of the butterfly, says, that such a change 

 of the tunic of the intestinal canal never happens, and that in the tracheae 

 it occurs only in the large main stems J. In fact, we must confess that 

 if the stripping of the skin is, as we have above remarked, merely 

 caused by its gradual hardening in the air, and the consequent impos- 

 sibility of the distension of the increasing body, it does not require that 

 we should thence admit of an equally requisite change of the internal 

 tunic of the intestinal canal, nor even of the tracheae, except in their 

 large main stems, into which much air passes, and that, therefore, 

 Bonnet's assertion reposes either upon a false observation, or was per- 

 haps wholly invented by him for the support of his theory of encase- 

 ment. But in opposition to this, independent of the credibility to 

 which a man like Bonnet may lay claim, the testimony of Swammer- 

 damm speaks, and who certainly did not lie, or say more than he saw : 

 he remarks, that at the posterior end of the stripped skin, where it is 

 twisted up and folded, he observed the moulted colon, and that after 

 the moulting of the larva of the rhinoceros beetle the internal tunic of 

 all the tracheae, even to their most delicate extremities, were visible in 

 the stripped integument . I have distinctly observed the same in the 

 moulting of the Libellulce ; in these, not merely the main stems, but 



* Contemplations dc la Nature, torn.ii. p. 48. -f Biblia Nature, pp. 129, 134, 239, &c. 

 $ Pp. 34. and 88. Biblia Naturae, p. 129, b. 



