148 NUNNELEY, ON THE CRYSTALLINE LENS. 
from the circumference to the axis from 555 to ; of an 
inch wide; and, as in all mammalia, the serrations are 
small. Fig. 8, shows a transverse section of a bundle of 
fibres from near the middle of the lens, in which the hexago- 
nal form of the fibres is seen. 
In the cat the fibres do not differ materially from those of 
other mammalia, but are very easily rendered irregular the | 
edge (fig. 9). 
In man the fibres differ but little from those of other 
mammalia. They are shown in fig. 10. 
The fibres are very flexible when in a natural condition, 
but after coagulation very easily broken ; hence they are re- 
presented by Arnold as made up of short portions ; but they 
are certainly long filaments, most of them passing from one 
surface of the lens to the other. The broader surfaces of the 
fibres appear to merely he in close apposition, where the 
layers are superimposed upon each other, and to adhere as 
all soft moist membranes do when in close contact, or, at 
most, to be weakly connected by mucus ; hence the lens far 
more readily separates into concentric layers than do the 
fibres from each other laterally. 
Kolliker describes the fibres to be thin-walled tubes filled 
with a clear viscid albuminous fiuid. In this, I think, he is 
in error, for though I have in some instances examined 
lenses where the central cylindrical filaments appeared to be 
tubular (particularly in the rat), they have been few and 
some days after death; and though sometimes the edges of 
the larger flat fibres present a darker lme, almost like a 
double wall, this is never seen sideways, and is probably only 
the effect of the edge of the fibres upon the hight when not 
fully in focus; while in every instance, whether of mam- 
malia, birds, reptiles, or fish, where the lens has been examined 
immediately after death, the appearance has been so constant 
that I think there can scarcely be a doubt that the filaments 
are really solid fibres—uniformly clear, transparent, and ho- 
mogeneous at first; but by heat, reagents, or decomposition 
soon becoming granular, then separating into granules and 
disappearing. These granules are smaller in birds and mam- 
malia than in reptiles and fish. The whole substance of the 
lens is harder and more dense in the latter classes than in the 
former, particularly in the fish as compared with the bird. 
In the latter the lens is soft and jelly-like throughout; the 
central portion, though more dense than the outer, is not so 
in anything like the same degree as it is in fish, where not 
only is the whole lens more firm, but the central part is m 
many genera of almost stony hardness, bemg difficult to cut 
