INTERNAL ANATOMY OF INSECTS. 65 
the scalpel of a Lyonet and the most powerful lenses 
are adequate to trace the extremities of these vessels ; 
and even with every help, they at last become so incon- 
ceivably slender as to elude the most piercing sight. 
That illustrious anatomist found that the two trachea of 
the larva of the Cossus gave birth to 236 bronchial tubes, 
and that these ramify into no less than 1336 smaller tubes, 
to which, if 232, the number of the detached bronchia?, 
be added, the whole will amount to 1804 branches \ 
Surprising as this number may appear, it is not greater 
than we may readily conceive to be necessary for com- 
municating with so many different parts. For, like the 
arterial and venous trees, which convey and return the 
blood to and from every part of the body in vertebrate 
animals, the bronchia; are not only carried along the in- 
testines and spinal marrow, each ganglion of which they 
penetrate and fill, but they are distributed also to the 
skin and every organ of the body, entering and travers- 
ing the legs and wings, the eyes, antennae, and palpi, and 
accompanying the most minute nerves through their 
whole course b . How essential to the existence of the 
animal must the element be that is thus anxiously con- 
veyed by a thousand channels, so exquisitely formed, to 
every minute part and portion of it ! Upon considering 
this wonderful apparatus we may well exclaim, This hath 
God 'wrought, and this is the work of his hands. 
Though in general there is only & pair of trachea:, yet 
in some larvae a larger number have been discovered. 
a Lyonet 411. » Professor Kidd (Philos. Trans. 
1825. 235.) conjectures that the tracheae, as well as air-vessels, may 
possibly be blood-vessels ; but this hypothesis is inconsistent with the 
fact recently discovered by Dr. Cams, of a circulation, by other 
means, in larvae. See Cams Introd. /<> Comp. Anal. &C\ ii. 400, 
VOL. rv. F 
