130 The Ciliary Muscle and Mort Eee Cine 
capsule, but the colloid mass is not a part of the capsule, it is some- 
thing superadded to it. 
I am aware that some good observers deny this origin of these 
intracapsular fibrous webs, which are not optically distinguishable 
from a connective substance. They ask how can a connective sub- 
stance be the derivative of an epithelium, and they maintain that 
in all these cases the capsule has not been entire, but it has had 
some rent through which these fibrous webs have intruded them- 
selves from without. I cannot yield to this opinion, because I 
have found such webs on the inner surface of capsules, which I could 
not doubt were entire and where their intrusion was impossible, 
and because I have, as I believe, been able to trace the evolution of 
the fibrous tissue from the epithelial cells through intermediate 
phases. A normal lens-fibre, which all allow is the final phase of 
a capsular epithelial cell, differs hardly less from its initial phase 
than do some of the elements of these fibro-nucleated webs. 
The posterior half of the capsule has not any epithelial lining, 
but its inner surface frequently exhibits polyhedral marks which 
have been mistaken for an epithelium. ‘They really express the 
hexahedral, oblique cross-sections of the swollen posterior ends of 
the lens fibres. 
The tissue composing the lens itself consists in greatest part of 
long, flat ribbon-like fibres. These have two wide surfaces and 
four narrow ones meeting in two thin bevelled edges, which give to 
their cross-sections a hexahedral figure. The fibres are really long 
tubes filled with the protein substance, to which chemists have 
given the name Globulin. When the fibres are broken across, it 
transudes in the form of globules from their ends. It often ac- 
cumulates in large masses between the layers of fibre in lenses, which 
have been hardened with chromic acid. 
A nucleus is present in the superficial fibres near the edge of 
the lens, but the deeper fibres are more sparingly nucleated. The 
fibres cohere very closely by their flat surfaces, and still more in- 
timately by their bevelled edges. ‘These latter in some vertebrates 
are serrated, which renders their union still more secure. This 
serration is very coarse in fish and in some chelonia, much finer in 
snakes, so fine in frogs that the edges appear only as if slightly 
frayed, and absent from the human lens-fibres. 
The other constituent of the lens is the interstitial tissue, a 
formless substance present in a very minute quantity in the axis of 
the lens, and in those extensions of it called the central or axial 
planes. In young persons the retractive index of this substance . 
agrees with that of the fibrous tissue; hence their lenses are free 
from the internal refleaions which the lenses of elderly persons 
exhibit, and which give these an opalescence which an incautious 
observer may readily mistake for a cataractous opacity. 
