( 231 ) 



XVI. Inquiry into the Structure and probable Functions of the 

 Capsules forming the Canal of PETIT, and of the Marsupium 

 Nigrum, or the peculiar Vascular Tissue traversing the Vitre- 

 ous Humor in the Eyes of Birds, Reptiles, and Fishes. By 

 ROBERT KNOX, M. D. F. R. S. ED., and Conservator of the 

 Museum of Ihe Royal College of Surgeons. 



(Read March 15. 1824J 



THE following additional observations on the comparative 

 structure of the eye-ball, are intended chiefly to illustrate the 

 philosophical anatomy and physiology of the capsules forming the 

 Canal of PETIT, and of the Marsupium Nigrum ; yet as I have 

 here taken notice of several other points in the comparative ana- 

 tomy of the eye, the memoir may be considered as supplemen- 

 tary to those formerly read to this learned Society, and which it 

 did me the honour to insert in its Transactions *. I have stated 

 in the first of those essays, that I had been led to inquire into 

 the structure of the Eye, partly as connected with researches 

 into the comparative anatomy of all the organs of sense, but 

 more particularly with a view to elucidate the nature and distri- 

 bution of the nervous system. I did not presume to think that 

 any remarkable peculiarities in the structure of this most inter- 

 esting organ, had escaped preceding anatomists ; but though I 

 found this to be true, in so far as regards the structure of the 

 eye in most of the mammalia, it yet appeared that the same or- 

 gan in other vertebral animals had by no means been investiga- 

 ted, or at least described, with the same care. 



* Vol. x. Part i. p. 43. 

 VOL. X. P. II. G g 



