566 STRUCTURE OF THE [SECT. 227. 



showing that such membranes, although apparently homogeneous, 

 are yet readily permeable; we can, therefore, easily understand 

 how the non-vascular lens can be supplied with nourishment by 

 substances penetrating from without. The capsule of the lens 

 measures, at its anterior wall, o"005'" to 0008"', but behind the 

 attachment of the zonule of Zinn, where it suddenly becomes at- 

 tenuated, only 0'002'" to 0003" in thickness; it can be readily 

 torn, pierced, or cut, but opposes considerable resistance to a blunt 

 instrument. If an uninjured capsule be pierced, it contracts, by 

 virtue of its elasticity, to such a degree, that the lens not unfre- 

 quently passes out spontaneously. The capsule of the lens presents 

 the same micro-chemical reactions as other vitreous membranes, 

 except that, according to Stralil {Arch. f. phys. Heilk, 1852), it is 

 dissolved by boiling in water. — The epithelium of the capsule of 

 the lens is not situated on the outer side, as Brilcke states, but 

 upon the inner surface towards the lens, and lines the anterior half 

 of the capsule as a simple layer of beautiful, clear, polygonal cells, 

 o , oo6'"to o'Oi"', with round nuclei. At death, its elements readily 

 separate from each other, and become distended into clear, sphe- 

 rical vesicles, many of which burst, and, together with some of the 

 aqueous humour which has penetrated the capsule, constitute the 

 so-called liquor Morgagni, which does not exist at all during life, 

 when the epithelium is accurately adapted to the surface of the 

 lens. 



The lens itself consists throughout, of long, flat, six-sided 

 elements, o - oo25'" to o - oo5'" broad, o - oooo/" to 0-0014'" thick, of 

 clear appearance, great pliability and softness, and of considerable 

 toughness. They are usually designated the fibres of the lens, but 

 they are, in reality, delicate-walled tubes, containing a clear, viscid, 

 albuminoid matter, which oozes out of them in large, clear, irre- 

 gular drops when they are torn ; such drops are always found in 

 large quantities on examining the superficial fibres of the lens, so 

 that these may be called with equal propriety, the tubes of the 

 lens. In a micro- chemical point of view, these tubes are distin- 

 guished by the circumstance, that they become darker and more 

 distinct in all substances which coagulate albumen ; and hence re- 

 agents of this class are excellently adapted for the investigation of 

 the lens, especially nitric acid, alcohol, creosote, and chromic acid ; 

 in caustic alkalies, on the other hand, they quickly dissolve, and 

 are likewise very strongly acted upon by acetic acid. The tubes 

 of the lens are firmer, narrower, and darker in the hard internal 

 layers of the lens than in the softer external parts, where they 



