242 DR KNOX on the Philosophical Anatomy 



tery, (which artery is obliterated very early in life), is totally 

 inadequate for its growth and support, even supposing that 

 this vessel should entirely belong to it. But anatomists, anxious 

 to ascertain the secreting vessels of the lens, and of its capsule, 

 have pushed their researches relative to the branch of the cen- 

 tral artery of the retina, which passes through the vitreous hu- 

 mor in the young of mammiferous animals, so far as nearly to 

 have proved, that this vessel is ramified chiefly on the capsule of 

 the crystalline. It is nevertheless true, that a few excessively 

 delicate branches from the artery, seem to belong exclusively to 

 the vitreous humor ; but these are totally inadequate to the se- 

 cretion of so large a mass, proceeding even on the supposition 

 (in all probability incorrect), that the vitreous humor once se- 

 creted, becomes, as it were, a dead body, placed without the 

 circle of the circulation, and no longer subject to decay or re- 

 novation. 



There is still another source whence the fluid composing the 

 vitreous humor might be derived. The branches of the central 

 artery of the retina, which are distributed in a beautiful net- 

 work over the inner tunic of the retina, proceed as far as the 

 zonule of ZINN, and are then lost upon the external parietes 

 of the canal of PETIT, and more particularly on those reduplica- 

 tions of this membranous body which I have called the Internal 

 Ciliary Processes. Still these anastomosing vessels are few, com- 

 pared with the almost innumerable branches the same processes 

 receive from the true or coloured ciliary processes, of which fact 

 I have already spoken. 



Although these researches have as yet been, in a great mea- 

 sure, confined to the eyes of quadrupeds, and animals nearly ap- 

 proaching them in structure, I yet feel assured that the inferences 

 are strictly applicable to the human eye. WALTER, as early as 

 1778, partly describes them in the following words: " Interna 

 superficies membranas choroideae has conducit ad venas capsulse 



