of the Canal of PETIT. 237 



the membrane to ZINN; but that distinguished anatomist argued, 

 that this was the corona ciliaris, which he considered as distinct 

 from the membrane of the retina. M. DE BLAINVILLE adopts 

 the opinion of HALLER. But whether or not we suppose the 

 inner membrane of the retina to be continued as far as the 

 crystalline, it is always to be remembered, that after it has 

 quitted the pulpy layer of the retina, it assumes a new form, 

 becoming exceedingly vascular, and has the same title to be 

 considered as a structure distinct from the tunica vasculosa 

 retinae, as the true ciliary processes are from the choroid. I 

 view both as merely appendages, and continuations of the re- 

 spective membranes to which they belong. The intimate depen- 

 dence of the internal ciliary processes on the vascular portion 

 of the retina in the mammalia, may be judged of by the fact 

 stated, that these processes cease to be vascular in birds, where- 

 ever the former no longer has distinct bloodvessels. Finally, I 

 do not think that this continuation of the inner membrane of 

 the retina contributes so essentially towards the formation of the 

 Canal of Petit as does the continuation of the hyaloid mem- 

 brane. 



By the employment of delicate vermilion injections, I find 

 that the ciliary processes of the vitreous humor (the Corona cili- 

 aris of ZINN) abound with bloodvessels. I beg leave to present 

 to the Society numerous preparations illustrative of so interest- 

 ing a point in the anatomy of the eye *. The union be- 







* The preparations illustrative of this and numerous other important points in 

 the structure of the eye, amount to forty-seven. A far greater number was destroyed,, 

 in order to perfect the researches connected with this and the preceding papers. Of 

 those preserved, thirty-six have been deposited in the Anatomical Museum of the 

 Royal College of Surgeons of Edinburgh ; and the remainder, a distinguished ocu- 

 list of this place did me the honour of placing in his own collection. These 

 preparations are intended to illustrate every important fact in the Comparative 

 tomy and Physiology of the Eye. 



