340 Dr Knox on the Com/parative Anatomy of the Eye. 
horse. Lastly, In most fishes, it is completely rudimentary, and 
is reduced to a mere ligament. 
2. When examined by the microscope, it puts on the same 
appearance as the iris, and presents the same arrangement of par- 
ticles. Now, the iris is avowedly muscular, or at least possesses 
the power of extensive motion ; and this at the least must be 
granted, even supposing the celebrated sphincter, and radiated 
fibres of the iris to be a pure fiction. 
3. The anatomist has only to examine the ciliary muscle in 
the eyes of birds, and in the fallow-deer, to be satisfied, that whe- 
ther the ciliary circle be muscular or not, it cannot possibly be 
a ligament. 
Lastly, In most birds, and in many of the mammalia, as in 
the quadrumanous and canine animals, numerous nerves can 
readily be demonstrated, proceeding to the ciliary muscle, and 
distributed throughout its substance. Now, every one knows, 
that ligaments are not supplied with nerves, or at least that the 
nervous fibrils proceeding to them, are so minute as entirely to 
escape the observation of the anatomist ; but the circular body, 
which hitherto hath been called the Ciliary Ligament, is abun- 
dantly supplied with nerves, in a ratio proportioned to the ac- 
commodating powers of the eye. In birds these nerves are very 
numerous, almost equalling in number the branches distributed 
to the iris. In the deer, and in apes, they may be very readily 
traced. The supply of nerves to the ciliary muscle in the eye 
of the horse is less abundant, though still very distinct ; but in 
fishes, where the ciliary muscle has altogether disappeared, or as- 
sumed the form and functions of a ligament, these nerves do not 
exist. This accords with the facts of pathological anatomy, 
which teach us, that wherever the nerves supplying an extremi- 
ty are wanting, the muscular system of that extremity has also 
disappeared. 
Whilst describing the sclerotica and transparent cornea. Dr 
Knox has endeavoured to unravel the true anatomical connec- 
tions of these membranes ; the reflected membrane of the cho- 
roid investing the inner surface of the sclerotic ; the mode of 
union between the sclerotic and cornea, and the existence of a 
reflected membrane from the latter covering the anterior surface 
of the iris in fishes, and in most birds. In the mammalia, the 
