238 DR KNOX on the Philosophical Anatomy 



tween the true ciliary processes, and the ciliary processes of the 

 vitreous humor, is chiefly vascular. Branches of the central 

 artery and veins of the retina likewise anastomose with those re- 

 ceived from the external ciliary processes : but such anastomo- 

 sing vessels are comparatively few. 



These dissections have explained to me a number of inter- 

 esting facts in the philosophical anatomy of the eye, which pre- 

 viously I could not understand, as they seemed totally uncon- 

 nected one with another. 



The Canal of Petit, as has been stated, is formed by two 

 layers or membranes quite distinct from each other. It is not 

 of much importance whether we view these as merely a conti- 

 nuation of the hyaloid and of the inner membrane of the retina, 

 (as I consider them really to be), or as being of a totally different 

 nature from these membranes. 



I have said in my former paper on the Comparative Anato- 

 my of the Eye (p. 19.), that, " from the internal surface of the 

 transparent ciliary body just described (the Zonule of ZINN) is de- 

 tached a membrane, which being inserted into the capsule of the 

 lens, somewhat more posteriorly or central, thus contributes to 

 complete the triangular-shaped Canal of Petit." But the pre- 

 parations I have now the honour to shew to the Society, de- 

 monstrate that the membranes forming the internal and external 

 parietes of the Canal of Petit, unite anteriorly with the capsule 

 of the lens, and ivith each other, occasionally by a very acute angle ; 

 and that it is from this point that a membrane seems to be trans- 

 mitted over the whole posterior surface of the capsule of the lens ; 

 but this membrane has nothing to do with the canal itself*. 



* We shall return to this fact more particularly in a future part of the memoir. 

 The descriptions usually given of the structure and formation of the Canal of Petit, by 

 anatomical writers and lecturers, are frequently quite unintelligible. 



