OTT Cee Crystalline Lens in Man. 221 
Separated by a wide interval from Crampton’s muscle in the eagle, 
as I have already said, in many smaller birds it appears on a cursory 
examination to be a continuation of the posterior fibres of this, yet 
on careful scrutiny always shows that it has distinct attachments. 
In many birds there is an accessory muscular slip attached ante- 
riorly to a prolongation of the same tendinous band from the 
cornea into which the inner ends of the fibres of Crampton’s muscle 
are inserted, and in some birds this muscular slip exceeds that 
which stretches from the sclerotic to the choroid. The contraction 
of either or of both these muscular slips would tend to drive the 
choroid forwards upon the sclerotic, and to tighten it upon its 
contents. They are tensors of the choroid and the homologues of 
the human ciliary muscle. 
The pecten, which before the ciliary muscles were known was 
once considered as the agent of accommodation, is not any longer 
considered so. I shall have occasion to refer to it in my next 
lecture. 
Reptiles have an iris very like that of birds. The primitive 
muscular fibres of the striped sort are extremely fine; they also 
exhibit divisions and a plexiform arrangement. They are also dis- 
posed in two sets, one circular, the other radiating, which difter 
from those of birds mainly in their minor development. Crampton’s 
muscle I have not found in any reptile’s eye, but all which I have 
examined, embracing several chetonia and many lizards and snakes, 
have a striped tensor of the choroid passing between the sclerotic 
and this coat, occupying the same posterior position as its homo- 
logue in the bird, and also functionally corresponding with human 
ciliary muscle. 
I have hitherto been baffled in every attempt to decipher the 
details of the muscular front of the accommodative apparatus in 
batrachia. The quantity and blackness of the pigment in the frog’s 
eye offers insuperable difficulties. An unstriped sphincter pupille 
is generally demonstrable. It is composed of long spindle-cells 
enclosing an elongated cylindrical nucleus with some granular pig- 
ment. How far it extends outwards, and whether any circular 
fibres reach the periphery of the iris, as in birds and reptiles, I am 
unable to say. Radial bundles of spindle-cells resembling those of 
the sphincter are also certainly present. 
Aris AND GALE Lectures II. 
The conjunctiva is a thin membraniform web of areolar tissue 
with an external epithelium. The structure of the palpebral part 
differs slightly from that of the ocular. The former is tougher, the 
latter has a looser texture. The palpebral partis beset with simple, 
