LETTER XXXV. 
EXTERNAL ANATOMY OF INSECTS, 
CONTINUED. 
THE TRUNK, AND ITS PARTS AND ORGANS. 
AS the head of insects is the principal seat of the organs 
of sensation, so is the trunk of those of motion; and in it 
are contained the muscles by which they are moved: it 
may therefore be regarded as the great centre of motion, 
and as the main support and prop of the two other pri- 
mary sections of the body—the head and abdomen, be- 
tween which it is situated—it may be deemed the most 
important part of the insect, the key-stone of the whole 
structure. In treating upon it, for the greater clearness, 
I shall consider its substance, general form, proportions, 
composition, internal processes, and members. It will first, 
however, be hecessary to assign my reasons for the no- 
menclature of its parts that I have adopted. 
Had the entomological world been universally agreed 
upon this subject, and there was an established system 
of Orismology*, I should have proposed no alteration 
* For the reason which induced the authors to use this word in- 
stead of Terminology, before employed, see Vor. I. Pref. p. xv—. 
They are cratified to see that M. Latreille has adopted this term in 
the work quoted on the other side, p. 194. 
