'182 PHYSIOLOGY. 



certainty than that in insects similar organs are found, to those whereby 

 the higher animals, and particularly man, feels, and that there- 

 fore, by means of these organs, insects likewise perceive the presence 

 and quality of the external objects which their body touches. But we 

 know, upon the other side, by means of direct observations, that insects 

 do feel, and we may therefore deduce from the preceding opinion, 

 founded upon analogy and these observations, that the nerves of insects 

 are likewise the organs of sensation. 



Observations confirmatory of the presence of sensation in insects- 

 daily offer ; we have but to look at some creeping insect, and observe how 

 it convinces itself of the presence of an object by touching it with its 

 antennae, and then carefully avoiding it ; and besides, insects that are 

 reposing are disturbed from their repose by any ungentle touch, and 

 upon a repetition of the disturbance quit the spot ; and lastly, pupa, 

 upon the least touch, and by their rapid and serpentine motions, 

 instantly evince a feeling of displeasure. In many pupae the sensation 

 of inimical influence is so delicate as scarcely to be credible ; the mere 

 opening of a box in which they may have been placed disturbs them, 

 and, indeed, some of the slightly clothed pupa of the Coleoptera, whose 

 natural situation is beneath the earth or in dark situations, instantly 

 move, and with considerable force, if a ray of light be allowed to fall 

 upon them, but they are peculiarly sensitive to bright sunshine. 



But we are most distinctly convinced of the sensation of insects upon 

 impaling them for the collection. Even the mere pressure of the pin 

 produces unpleasant sensations, which the insect expresses by the rapid 

 and painful motion of its limbs ; upon its point proceeding still further 

 the expression of disagreeable feeling increases by its more rapid and 

 unnatural contortions, and I have frequently observed, that at the mo- 

 ment when probably the pin passed through the ganglion, and when the 

 insect appeared as it were suddenly lamed by its excessive pain, it 

 extended all its limbs, and even its oral organs, and then ceased for 

 some seconds all motion. This motion continues for some space of 

 time, frequently from a week to a fortnight, as long as the insect is 

 teased, but it does not appear to happen in repose, or if the insect be 

 enclosed in a dark situation, at least I have observed many instances 

 in which, under such circumstances, the insect did not move. Hence, 

 as well as from the subordinate sensibility of the nervous system of the 

 lower animals, we may conclude that insects thus impaled no longer 

 feel any pain, and that their motion is produced merely by their emlea- 



