204 Dr. Hosack's Observations on Vision. 
layers possess no distinct muscles is, that in this opaque state 
they are not visible, but consist rather of an almost infinite 
number of concentric fibres (if the term be at all appropriate) 
not divided into particular bundles, but similar to as many of 
the finest hairs of equal thickness, arranged in similar order : 
see fig. 4, 5, and 6 , where the arrangement of the layers and 
fibres has been painted from the real lens of an ox, and that 
without the assistance of a glass. To observe this fact, any 
person may try the experiment at pleasure, and witness the 
same with the naked eye, even separating many layers and 
their fibres with the point of a penknife. 
This regular structure of layers, and those consisting of con- 
centric fibres, is unquestionably better adapted for the trans- 
mission of the rays of light, than the irregular structure of 
muscles. It may, perhaps, be urged, that the heat to which 
I exposed the lens may have changed its structure : in answer 
to that I observe, it was moderate in degree, and regularly 
applied ; of consequence we may presume, as it appeared uni- 
formly opaque, that every part was alike acted upon ; but by 
boiling the lens, where the heat is, without doubt, regularly 
applied, we observe the same structure. 
Thirdly, that it is not from any changes of the lens, and 
that this is not the most essential organ in viewing objects at 
different distances, we may also infer from this undeniable 
fact, that we can, in a great degree, do without it ; as after 
couching or extraction, by which operations all its parts must 
be destroyed, capsule, ciliary processes, muscles, & c. 
Mr. Young asserts, from the authority of Dr. Porter- 
field, that patients, after the operation of couching, have not 
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