EYE. 



193 



which is very feeble; it thus becomes godronne. 

 If the crystalline be removed from its capsule 

 without injuring the membrane which forms 

 this canal, these godronne folds are not formed by 

 inflation or only in a very slight degree, but the 

 canal becomes larger. It is in man commonly 

 a line and a quarter, a line and a half or two lines 

 in breadth, and not larger in the ox." An- 

 nexed is a representation of this canal of Petit 

 on a large scale. 



Ji. 115. 



Fig. 116. 



As the nature of the connection between 

 the choroid and the hyaloid membrane, the 

 formation of the posterior chamber of the 

 aqueous humour, and the structure of this 

 canal of Petit, have been the subject of contro- 

 versy, I venture to introduce here an extract 

 on this subject from the paper published by 

 me in the Medico-Chirurgical Transactions. 



" If the sclerotic, choroid, iris, and retina 

 be removed one or two days after death, leaving 

 the vitreous humour with the lens embedded 

 on its anterior part, we observe a number of 

 stria on the vitreous humour, converging 

 towards the circumference of the lens, cor- 

 responding in number, size, and form to the 

 ciliary processes, giving the same appearance 

 collectively that the circle of ciliary processes 

 or corpus ciliare does on the choroid, and nar- 

 rowed towards the nasal side as the corpus 

 ciliare is. This appearance has been noticed 

 by most authors, but some describe it as 

 arising merely from the marks left by the 

 ciliary processes, while others consider these 

 stria of the same nature as those productions 

 of the choroid, and call them the ciliary pro- 

 cesses of the vitreous humour ; it is the corona 

 cifiaris of Camper and Zinn. If we remove 

 the black pigment with a camel-hair pencil, we 

 leave those productions on the vitreous humour 

 more distinctly marked than when covered by 

 the colouring matter, and presenting all the 

 characters above stated, commencing behind 

 with a well-defined margin, and terminating 

 anteriorly by attachment to the capsule of the 

 lens, the furrows between them capable of 

 receiving the ciliary processes of the choroid, 

 and the folds calculated to be lodged in the 

 corresponding furrows of these processes. The 

 annexed figure is a representation of the vitreous 

 humour of the human eye thus treated. 



" If the cornea and iris be removed from a 

 human eye within a few hours after death, a 

 dark circle surrounding the lens, between it 

 and the anterior extremities of the ciliary pro- 

 cesses, may be observed : this is the part of 

 the corona ciliaris of the vitreous humour to 

 which the ciliary processes of the choroid do 

 not extend, which appears dark on account of 

 its perfect transparency ; the converging stria 

 are evident, even on this part where the ciliary 

 processes are not insinuated, interrupting the 

 view if we attempt to look into the bottom of 

 the eye by the side of the lens. It is, in my 

 opinion, therefore certain, that part of the 

 vitreous humour enters into the formation of 

 the posterior chamber of the aqueous humour. 

 The demonstration of this fact is, however, 

 attended with difficulty, because the flaccidity 

 arising from even slight evaporation of the 

 fluids of the eye permits the ends of the ciliary 

 processes which present themselves in the 

 posterior chamber of the aqueous humour to 

 fall towards the circumference of the lens, and 

 appear attached there. For myself I can say 

 that having made the dissection in the way just 

 pointed out, the eye of course in water, and 

 beneath one of those globular vessels which 

 I formerly described, I could see to the bottom 

 of the eye through the space in front of the 

 vitreous humour, between the ciliary processes 

 and the margin of the lens ; this space is, 

 however, perhaps larger in some individuals 

 than in others. Each fold of the corona ciliaris 

 of the vitreous humour seems to consist of two 

 layers of hyaloid membrane, capable of being 

 separated one from the other byinflation, and ad- 

 mitting of communication with each other round 

 the lens. It appears to me that the canal of Petit 

 or canal godronne is formed in consequence of 

 these folds receiving the injected air one from 

 the other ; it is, however, generally described 

 as being formed by the membrane of the 

 vitreous humour splitting at the circumference 

 of the lens, one layer going before and the 

 other behind that body, the canal existing 

 between these two layers and the capsule of 

 the lens. That the capsule of the lens has no 

 share in the formation of the canal of Petit, I 

 conclude from filling this canal with air, and 

 allowing the part to remain for some days in 

 water, and then with great care removing the 

 lens included in its capsule ; this I do not find, 

 however, causes the air to escape from the cells, 

 but leaves them presenting nearly the original 

 appearance ; and after the air has escaped, I 

 can pass a small probe all round in this canal, 



o 



