274 Befcription of the Eye of the Seal. 



yf Description of the Eye of the Seal; by Mr. 

 Hey, of Leeds. 



READ OCTOBER 26, I787. 



IN the debate concerning the immediate organ 

 of vifion, it has been aflerted, and is taken 

 for granted by the beft authors, that the eyes 

 of the feal and porcupine are differently formed 

 from thofe of other animals; having the optic 

 nerve inferted in the axis of the pupil. This 

 difference of ftruiture has been urged as an 

 argument to prove, that the retina is that part 

 of the eye which receives the pidlure, and con- 

 veys to us the idea of external obje<51s. For 

 fince, according to the laws of optics, the pic- 

 ture mull be formed in and about the axis of 

 the pupil; and fince the choroides is wanting 

 at the infertion of the optic nerve, the choroid 

 coat cannot, in thefe animals, receive the com- 

 plete piclure of any objeifl. 



Though the argument fails with refpeft to 

 the animal whofe eye I am about to defcribe, 

 yet I do not mean to exprefs any doubt that the 

 retina is the proper organ of vifion. The pre- 

 ceding obfervation is mentioned as that which 

 excited my curiofity to know, whether this de- 



_-viation 



