Dr Knox on file Compiifdiwe Uinatomp (^the 'Eye, 
the power of changing the position of its parts by some means 
or other, and these must be placed either within it, or exteriorly 
to it. It would be tedious tb enumerate all the Various opinions 
which have been entertaihed on this subject, most of which have 
either been directly refuted by an appeal to facts, or, from be- 
ing evidently defective and imperfect, have been suffered to fall 
into merited oblivion. Every one knows that this futictioh has 
by some been assigned to the iris ; by others to the ciliary liga- 
ment; to the ciliary processes; to the lens; to the external 
muscles of the eye-ball; and even to the marsupium,-— a very 
singular bpinion,' since the marsupium being limited to birds arid 
certain fishes, it remained to be sliewn by what structure the 
function was performed in the other classes of vertebral animals. 
Mr John Hunter, to whom physiology is so greatly indebt- 
ed, was engaged, a short time previous to his death, in the in- 
vestigation of this subject. The appearance of the lens in the 
cuttle-fish seemed strongly to have arrested his 'attention, and 
he seemed inclined to attach to the structure of this humor of 
the eye, an importance which further inquiry would have shewn 
to be unmerited. Dr Knox has endeavoured to demonstrate 5 
that the changes which take place in the interior of the eye, by 
which we are enabled to percei ve objects at various distances, 
are effected by means of the ciliary muscle, or that body which 
anatoriiists have hitherto called the Ciliary Ligament, Anriulus 
albus. Sec. To prove this satisfactorily, required a most exten- 
sive series of dissections, during the performance of which, the 
prevailing errors regarding the nature of the ciliary muscle be- 
came more and more apparent. It is true, that many writers 
have considered the annulus albus as muscular, and founded 
thereon ingenious speculations; but as their 'opinion rested; for 
the most part, on bare assertion, so it was very generally, or al- 
most universally, neglected by modern physiologists. It will be 
necessary to state here only a few of the facts supporting this 
‘opinion. 
1. The development of the ciliary muscle ffollows fhe ratio of 
the strength of vision, or rather of the accommodating powers 
of the eye, in the various classes bf animals; L e, it is strong in 
%irds, in men, in the quadrumana, and in the deer ; weaker in 
some others of the ruminantia, as the ox ; still more so in the 
