146 NUNNELEY, ON THE CRYSTALLINE LENS. 
essentially of the same character, flattened, ribbon-like’ 
filaments, arranged side by side, so as to make a continuous 
layer, and connected, or interlocked together at their sides 
by serrations, which pass mutually into each other, just as 
the cranial bones do at the coronal and sagittal sutures. 
These serrations are by no means usually so uniform in size 
or number as they have been figured by Sir D. Brewster,* 
and they appear to me to be produced much in the same way 
as those in the cranial bones are, by the development and 
pressure of the fibres laterally against each other, and to 
result from the granules, of which the fibres are ultimately 
made up, pressing into the interstices of each neighbouring 
fibre ; for they are most distinct in the fibres of the hardest 
lens, and the serrations are largest and boldest where the 
granules are the largest. They are better marked where the 
filiform character is best developed, as in the middle rather 
than at the axis or margin of the lens, and the serrations 
become particularly developed by those reagents, which have 
a corrugating effect upon the fibres, as chromic acid and 
sulphuric ether. 
The fibres pass from one surface of the lens to the other, 
but whether every individual fibre does so, as stated by 
Brewster, is, I think, very doubtful; indeed, it is scarcely 
possible that all those near to the axis should do so, and, I 
think, many may be seen towards either pole becoming so 
attenuated as to be lost in, and amalgamated with, neigh- 
bouring fibres, the serrated edges and individual character 
being entirely lost. Each fibre is considerably broader at its 
middle than at its ends, towards which it gradually tapers, so 
that the greater width of the diameter of the lens over that 
of the axis is rather caused by the increase laterally in the 
middle of the fibres than by an additional number of fibres at 
this part. The depth or thickness of the fibres does not vary 
like the width, it appears pretty uniform in all the layers; 
hence, while the outer fibres are broad and ribbon-lke, the 
inner are almost cylindrical when separated, and when seen 
closely packed together in a bundle they appear hexagonal. 
This has doubtless led some observers into the error of de- 
scribing them as hollow tubes. Leeuwenhock described the 
number of layers as 2000 in the lens of a cod, and Sir D. 
Brewster calculated the number of fibres in each layer of the 
lens of a cod at 2500, and of the serrations in each fibre as 
* If a lens (of the cod, for instance) be strongly coagulated and then 
well dried, and a layer of the fibres be seen, the serrations are more uniform 
and regular than if a single detached fibre be seen or they are in the recent 
state. 
