CONSIDERATIONS. 143 



Amongst a great number of observations made upon the 

 nervous system of the articulated animals, which have led to 

 the discovery and verification of the laws of relation given 

 above, the genus Blaps is the only one that has formed an 

 exception. The segments of the abdomen are here anchy- 

 losed inferiorly, and above are so encased by the elytra, 

 which are connate, as to be incapable of motion ; yet we find 

 the ganglia repeated in the abdomen, as they would be did it 

 enjoy the power of motion. Probably this is owing to some 

 secondary cause, which modifies the result of the primary 

 causes. 



The nerves are covered, as in Vertebrata, with a neurilema 

 which can easily be separated. This coat is thick upon the 

 ganglia and spinal chords, much thinner on the nerves. The 

 nervous substance appears scarcely to diflfer from that of Ver- 

 tebrata, being formed of two parts, the one, the cortical, is 

 brown, the other, the medullary substance, white. 



In concluding this article, I cannot but express the regret I 

 feel at my utter inability to do justice to M. Straus ; first, 

 from not possessing a sufficient degree of knowledge of ana- 

 tomy in general, and secondly, from a want of sufficient leisure 

 to give to this paper that care which it required. This last 

 must also be my excuse for omitting much interesting matter, 

 especially that which relates to the senses and instinct of these 

 animals. I may here make one remark on the subject of the 

 antennae. M. Straus regards these as the organs of hearing ; 

 and this conjecture certainly receives some support from the 

 fact, that the nerve, supposed to be the auditory nerve of 

 Crustacea, is a branch of the antennal. But surely this is 

 but a slight foundation to build upon ; with equal reason 

 might we assert that the antennal nerve cannot be the auditory 

 nerve, because in the higher animals it always arises from the 

 posterior part of the brain. One thing, however, may be said 

 on this subject. It has been clearly proved that the sense of 

 hearing does not solely depend on the ear, or at least the 

 brain itself is capable of hearing sounds. When the ears 

 were hermetically closed, a patient upon whom the operation 

 of trepanning had been performed, could distinctly hear the 

 ticking of a watch, and even understand conversation at some 

 distance ; but on the aperture of the skull being closed, by 

 placing the hand over it, no sounds could be heard. I will 



