2 INTERNAL ANATOMY OF INSECTS. 



ticular apparatus ; nutrition is effected through a stomach 

 and intestines ; the analogue of the Hood prepared by 

 these organs pervades every part of the body, and from 

 it are secreted various peculiar substances ; generation 

 takes place, and an intercourse between the sexes, by 

 means of appropriate organs ; and lastly, motion is the 

 result of the action of muscles. Some of these functions 

 are, however, exercised in a mode apparently so dissimi- 

 lar from what obtains in the higher animals, that upon 

 a first view we are inclined to pronounce them the effect 

 of processes altogether peculiar. Thus, though insects 

 respire air 9 they do not receive it by the mouth., but 

 through litttle orifices in the sides of the body ; and in- 

 stead of lungs, they are furnished with a system of air- 

 vessels, ramified ad injinitum, and penetrating to every 

 part and organ of their frame ; and though they are nou- 

 rished by a fluid prepared from the food received into 

 the stomach, this fluid, unlike the blood of vertebrate 

 animals, is white, and the mode in which it is distributed 

 to the different parts of the system, except in the case of 

 the true Arachnida, in which a circulation in the ordi- 

 nary way has been detected, is altogether obscure. 



In order that you may more clearly understand the 

 variations that occur in insects, and in what respects 

 they differ amongst themselves, and from the higher ani- 

 mals, in the vital functions and their organs, I shall con- 

 sider them as to their organs of sensation, respiration, 

 circulation, nutrition, generation, secretion, and muscular 

 motion. 



Organs of Sensation. The nervous system of animals 

 is one of the most wonderful and mysterious works of 



