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XXXVITI. On the Anatomical and Optical Structure of the 
crystalline Lenses of Animals, particularly that of the Cod. 
By Sir Davip Brewster, LZ.D., F.R.S., V.P.RS. Ed. 
[ With a Plate. ] 
[From the Philosophical Transactions for 1833, p. 323-332; 
with additions. ] 
AVING observed very singular phzenomena in the cry- 
stalline lenses of fishes and quadrupeds when exposed to 
polarized light, I was led to examine their anatomical struc- 
ture, with the view of ascertaining if it had any relation to 
these optical appearances. Leeuwenhoek and Sattig had pre- 
viously made some progress in this research, but their methods 
of observation were ill fitted for so delicate an inquiry, and 
experience soon convinced me that the structure of the lens 
could not be thoroughly investigated either by the microscope 
or the scalpel. 
Anatomists had long regarded the crystalline lens as com- 
posed of concentric laminz, and these laminze of minute fibres; 
but M. Soemmerring, in his work on the Human Eye, pub- 
lished in 1804, regards this structure as the effect merely of 
maceration in alcohol, and maintains that it does not exist in 
the recent or the living eye*. This decision, which its author 
has supported by many plausible but unphilosophical and in- 
efficient arguments, appeared to set aside all the results which 
had been obtained by preceding inquirers, and rendered it 
necessary for me to adopt a new mode of investigation, which 
should not be liable to the same criticism. 
The crystalline lens of the cod, like almost all globular 
lenses, has the form of a prolate spheroid, the axis of revolu- 
tion being a little longer than the equatorial diameter. ‘This 
axis is the axis of the eye, or of vision. 
The body or substance of the lens is inclosed in an exceed- 
ingly thin and transparent membrane, called its capsule; and 
this membrane is so elastic that when it was stretched upon a 
plate of glass, the extended portion polarized a blueish white 
tint of the first order. If we puncture the capsule, a thickish 
fluid flows from the opening ; ; but upon removing the capsule 
altogether, this fluid is found to constitute only the outer coat 
of the lens, the substance of the lens growing denser and 
harder as we approach to the centre of it. 
The body of the lens is not connected with the capsule, as 
* “Lens, post mortem ita tractata, etiamsiin segmenta spheerica, laminas 
et fibras dehiscat, tamen minime inde sequitur lentem recentem seu vivam 
ex ejusmodi fibris, lamellis et segmentis spheericis conflari, aut per vitam 
lentis sanz fabricam zeolitidi ullo modo similem esse.”—pp. 67, 68. 
Third Series. Vol. 8. No. 46. March 1836. ee 
