CRUSTACEA. 341 



for some of them undoubtedly proceed from the cineritious portion 

 of the ganglionic swelling, while others, derived from the upper 

 column, not only have no connection with the grey matter, but 

 arise at some distance from the ganglion (fig. 138) : judging, 

 therefore, by the laws at present established in physiology, there 

 seems reason to suppose that the anterior or rather inferior fasciculi 

 are connected with sensation, while the superior constitute the 

 motor tract. 



The reader who is conversant with human physiology will at 

 once perceive that this arrangement is precisely the reverse of 

 that met with in man and other VERTEBRATA : and this consi- 

 deration, apparently of little importance, has given rise to a va- 

 riety of curious speculations ; some anatomists having even gone 

 so far as to assert that all the organs of articulated animals are 

 in reality placed in a similar inverted position. 



(376.) A more interesting inquiry connected with this part of 

 our subject is, concerning the extent to whrch the ARTICULATA 

 are susceptible of pain. Is it really true in philosophy, as it 

 has become a standing axiom in poetry, that 



" the poor beetle, that we tread upon, 



In corporal sufferance feels a pang as great 



As when a giant dies" ? 



This is a question upon which modern discoveries in science 

 entitle us to offer an opinion, and the result of the investigation 

 would seem to afford more enlarged views relative to the benefi- 

 cence displayed in the construction of animals than the assertion of 

 the poet would lead us to anticipate. Pain, " Nature's kind 

 harbinger of mischief," is only inflicted for wise and important 

 purposes, either to give warning of the existence of disease, or as 

 a powerful stimulus prompting to escape from danger. Acute 

 perceptions of pain could scarcely, therefore, be supposed to exist 

 in animals deprived of all power of remedying the one or of 

 avoiding the other. In man the power of feeling pain indubitably 

 is placed exclusively in the brain ; and, if communication be cut off 

 between this organ and any part of the body, pain is no longer 

 felt, whatever mutilations may be inflicted. 



The medulla spinalis, which, as we shall see hereafter, corre- 

 sponds to the ventral chain of ganglia in articulated animals, can 

 perceive external impressions and originate motions, but not feel 

 pain ; hence we may justly conclude that in the Homogangliata, 

 likewise, the supra-oesophageal ganglia, the representatives of the 



