7 
on the Structure of Nerves. 
brain, and smaller in the spinal marrow ; they had no regular 
order : but, in the nerves, the globules were placed in lines, so 
as to give the appearance of fibres. In examining the optic 
nerve, the parts were magnified 120 times. 
Prochaska considered the nerves to be composed of globules, 
united by a transparent elastic cellular membrane, and dis- 
posed in straight lines, resembling fibres. 
Fontana found the primitive structure of nerves to consist 
of transparent cylinders, which, when united, formed the nerve : 
the manner of their being disposed is not mentioned. The ob- 
jects were magnified 700 times, to show this appearance. 
Dr. Monro considered the nerves as made up of spiral fibres ; 
but afterwards found that what he had described was entirely 
an optical deception. In his last work, he says, “ The optic 
“ nerves have, in their whole course, less appearance of a fibrous 
“ structure than perhaps any other pair of nerves in the human 
“ body/’ 
Other authors may have written upon this subject, and may 
have made observations upon the structure of nerves, but 
want of leisure must be an excuse for my not having come to 
a knowledge of them. 
It is scarcely necessary to mention, that parts of an animal 
body are not fitted for being examined by glasses of a great 
magnifying power ; and, wherever they are shewn one hun- 
dred times larger than their natural size, no dependance can 
be placed upon their appearance. 
In making the following microscopical experiments on the 
internal structure of the optic nerve, great care was taken to 
avoid the errors of former inquirers. The microscope used 
was a single one ; the focal length of the lens was about 
