200 



EYE. 



from the lenticular. They never present the 

 stellated appearance frequently observed when 

 the texture of the opaque lens opens in the cap- 

 sule as it does when macerated in water, nor the 

 uniform horny or the milky blue appearance of 

 common lenticular cataract. The opacity in 

 capsular cataract exists in the shape of irregular 

 dots or patches, of an opaque paper-white ap- 

 pearance, and when touched with the needle are 

 found hard and elastic, like indurated cartilage, 

 the spaces between the specks of opacity fre- 

 quently remaining perfectly transparent. 



It appears to be generally assumed by writers 

 on anatomy that a watery fluid is interposed 

 between the body of the lens and its capsule, 

 from an incidental observation of Morgagni 

 when discussing the difference in density be- 

 tween the surface and centre of the lens; hence 

 it has been called the aqua Morgagni. The 

 observation of this celebrated anatomist, in his 

 Adversaria Anatomica, which has led to the 

 universal adoption of this notion, is, however, 

 merely that upon opening the capsule he had 

 frequently found a fluid to escape. " Deinde 

 eadem tunica in vitulis etiam, bobusque sive 

 recens, sive non ita recens occisis perforata, 

 pluries animadverti, illico humorem quendam 

 aqueum prodire : quod et in homine observare 

 visus sum, atque adeo credidi, hujus humoris 

 secretione prohibita, crystallinum siccum, et 

 opacum fieri fere ut in extracto exsiccatoque 

 crystalline contingit." He does not, however, 

 subsequently dwell upon or insist upon the 

 point. I do not believe that any such fluid 

 exists in a natural state, but that its accumula- 

 tion is a consequence of loss of vitality ; the 

 water combined with the solid parts of the lens 

 escaping to the surface and being detained by 

 the capsule, as occurs in the pericardium and 

 other parts of the body. In the eyes of sheep 

 and oxen, when examined a few hours after 

 death, not a trace of any such fluid can be 

 detected, but after about twenty-four hours it 

 is found in considerable quantity. In the 

 human eye a fluid sometimes accumulates in 

 the capsule, constituting a particular form of 

 cataract, which presses against the iris, and 

 almost touches the cornea ; but such eyes are, 

 I believe, always unsound. From this erro- 

 neous notion of an interposed fluid between 

 the lens and its capsule has arisen the adop- 

 tion of an unsustained and improbable conclu- 

 sion, that the lens has no vital connexion with 

 its capsule, and consequently must be produced 

 and preserved by some process analogous to 

 secretion. Respecting this matter I have ob- 

 served, in the paper above alluded to, " The 

 lens has been considered by some as having no 

 connexion with its capsule, and consequently 

 that its formation and growth is accomplished 

 without the assistance of vessels; such a notion 

 is so completely at variance with the known 

 laws of the animal economy, that we are justi- 

 fied in rejecting it, unless supported by un- 

 questionable proof. The only reasons which 

 have been advanced in support of this conclu- 

 sion are, the failure of attempts to inject its 

 vessels, and the ease with which it may be 

 separated from its capsule when that mem- 



brane is opened. These reasons are far from 

 being satisfactory; it does not necessarily 

 follow that parts do not contain vessels, be- 

 cause we cannot inject them; we frequently 

 fail when theie can be no doubt of their exist- 

 ence, especially where they do not carry red 

 blood. I have not myself succeeded in in- 

 jecting the vessels of the lens, but I have not 

 repeated the trial so often as to make me 

 despair of accomplishing it, more especially 

 as Albinus, an anatomist whose accuracy is 

 universally acknowledged, asserts, that after a 

 successful injection of the capsule of the lens, 

 he could see a vessel passing into the centre of 

 the lens itself. Lobe, who was his pupil, 

 bears testimony to this. The assertion that 

 the lens is not connected with its capsule, I 

 think I can show to be incorrect; it has been 

 made from want of care in pursuing the inves- 

 tigation, and from a notion that a fluid exists 

 throughout between the lens and its capsule. 

 When the capsule is opened, its elasticity 

 causes it to separate from the lens ; especially 

 if the eye be examined some days after death, 

 or has been kept in water, as then the lens 

 swells, and often even bursts the capsule and 

 protrudes through the opening, by which the 

 connexion is destroyed. I have however satis- 

 fied myself that the lens is connected with its 

 capsule (and that connexion by no means 

 slight) by the following method. I remove 

 the cornea and iris from an eye, within a few 

 hours after death, and place it in water, then 

 with a pair of sharp-pointed scissors I divide 

 the capsule all round at the circumference of 

 the lens, taking care that the division is made 

 behind the anterior convexity, so that the lens 

 cannot be retained by any portion of the cap- 

 sule supporting it in front. I next invert the 

 eye, holding it by the optic nerve, when I find 

 that the lens cannot be displaced by agitation, 

 if the eye be sufficiently fresh. In the eye of 

 a young man about six hours dead, I found 

 that, on pushing a cataract needle into the lens, 

 after the anterior part of the capsule had been 

 removed, I could raise the eye from the bottom 

 of the vessel, and even half way out of the 

 water, by the connexion between the lens and 

 its capsule. It afterwards required consider- 

 able force to separate them, by passing the 

 needle beneath the lens, and raising it from its 

 situation. I believe those who have been in 

 the habit of performing the operation of ex- 

 traction, have occasionally encountered consi- 

 derable difficulty in detaching the lens from 

 its situation after the capsule had been freely 

 opened, this difficulty I consider fairly refer- 

 able to the natural connexion just noticed." 

 When the lens enclosed in its capsule is de- 

 tached from the hyaloid membrane, the con- 

 nexion between it and the capsule is destroyed 

 by the handling, and, in consequence, it moves 

 freely within that covering, affording to those 

 who believe that there is no union between the 

 two surfaces fallacious evidence in support of 

 that opinion, which, if not sustained by better 

 proof, should be abandoned. Dr. Young in- 

 sists upon the existence of the natural con- 

 nexion by vessels and even by nerves between 



