crystalline lens in fishes and quadrupeds. 315 
and exposed to polarised light, it had the appearance shown 
in Fig. 5, in whatever position it was held,”'ffie vr fifghest tint 
being an orange yellow of the first order. By exatfiining 
these sectors #ith sblphate of lime, I found that the glass had 
the same structure as the middle coats of the Crystalline. In 
like manner, it appeared that the sectors, exhibited by press- 
ing a convex lens upon a flat piece of glass, were produced 
by a structure the same as that of the central nucleus of the 
crystalline. The structure of the crystalline lens, in short, 
is similar to that of a plate of glass that gives the unusual 
fringes* bent into a circular shape. Hence it follbws , that the 
central nucleus a?id the external coat are in a state of dilatation, 
while the intermediate coats fire in a state of contraction; and that 
these opposite states are not dependent upon each other ds in crys- 
tallized glass. 
The phenonien ! a%hlch' : have ■nh'w been described are Visible 
also in the crystalline of th d haddock. They appear likewise 
in that of sheep and oxen, but there is here only one series of 
luminous sectors corresponding with the intermediate set in 
the crystalline of fishes; 5 The human crystalline ’Will ho doubt 
display similar properties, but in an inferior degree. 
The cornea both of fishes and quadrupeds, and also the 
human cornea, have an analogous structure ; in which the 
optical axes of all the particles are directed to its centre. Its 
structure is the same as that of the internal nucleus, and it 
produces an effect upon polarised light similar to what is 
shown in Fig. 6. 
The sclerotic coat of fishes has the property of depolarising 
light in separate spots like the diamond, or a mass of crushed 
f See Phil. Trans. iSi 6, p, 65, 66. 
. - ' Tt 
MDCCCXVI 
