50 SUPPLEMENT ON 



the socket itself ; c, c, the tunick ; tZ, the pyramidal fasci- 

 culus ; e, the membrane, called by Cuvier the choroid ; /, 

 bundle of fibres, which is drawn in this and the other figures, 

 larger than in its due proportion, the better to display its 

 construction ; g, the nervous chord communicating directly 

 with h, a lobe of the brain. 



To these figures we have added : Fig. 15. The head of a 

 moth with the plumage removed, shewing the cranium horny 

 and granulated, the configurations on the eyes ; and Fig. 16, 

 a vertical section of the same to display the general appear- 

 ance : «, o, the pyramidal fasciculi as attached to the cornea, 

 forming a point where they come in contact with 6, h, the 

 choroid membrane passing through the same, and proceed- 

 ing in the shape of nervous chords or fibres to c, c, the lobe 

 of the brain. 



What are here delineated may be called the grosser parts 

 of this wonderful organ, for besides these, we have these 

 vessels incident to its existence, passing from the first gan- 

 glion called the brain, in various directions, through which 

 the air is conveyed, a fluid which seems indispensable to the 

 energy and application of the whole organ. The utmost 

 powers of the microscope with difficulty disclose to us the 

 largest of these airducts, but their almost infinitely minute 

 ramifications elude all human powers of investigation. Much 

 may be demonstrated to our senses, but much is at the same 

 time left to imagination. 



How little is it that we discover of the grand economy of 

 organized beings ! a very small portion only of its grosser 

 forms. The more minute and curious details defy our most 

 laborious research, and act silently and unseen, save only 

 to their omnipotent mechanic. Limited faculties soon arrest 

 our progress, even in physical science, but the very entrance 

 to metaphysical knowledge is hermetically closed against us ; 

 our utmost researches cannot ascertain, nay, even the most 



