10 



selves, and in the higher animals, we may reasonably con- 

 clude, when we see tissues of similar appearance pro- 

 fusely distributed about the reservoirs of aliment, in lower 

 forms of being, that these are the instruments of a similar 

 operation just as when we see that from different points 

 along the nervous trunk, there proceed branches ^oing to 

 parts subservient to the motions of the creature, we can- 

 not make much mistake in calling these latter expansions of 

 the nervous tissue nerves of motion. 



So far, some analogy in insects with man's structure 

 really obtains ; but when we come to enquire into their 

 probable possession of nerves of sensation also, let us see 

 how the case lies. First, we have no right to say that it is 

 necessary they should feel at all. Granting sensation how- 

 ever, that is conceding the point to be proved, we should 

 be exceedingly embarrassed to assign particular nerves 

 as their nerves of sensation. The other functions above 

 alluded to must, as we have seen, be executed in insects 

 equally as in man. As to sensibility, however, or its amount, 

 it could not, in the first place, have been assumed from 

 any abundance of nerves ; but the nerves in insects are few, 

 and the duties which those nerves seem to discharge having 

 been inferred from functions actually performed, and from 

 the visible distribution of the nervous matter, the resi- 

 duary legatee, Sensation, will come poorly off, unless we 

 assume that it may be imparted by the same nervous 

 material, wherever found, which has so many other 

 claims to satisfy. So much, then, for the probability 

 of Sensation in insects, from an examination of their system 



* Swammerdara, who has done so much for entomology, car- 

 ried insect anatomy to a perfection which, before his lime, seemed 

 impossible, and is therefore held in the highest reverence among 

 entomologists; not that I would venture, before the learned Society 

 of which I am a member, to aver my belief in all his discoveries. 

 A great deal of uncertainty as well as instruction must ever attach 

 to reasonings founded upon comparative anatomy ; only think of 

 differences of opinion as to whether a particular organ in an insect 

 should be called its spleen or liver. 



