Sir Everard Home on the 
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of-- 1 -- parts, the size of the red globules deprived of their 
colouring matter. 
The retina appeared as a continuation of the bundles com- 
posing the optic nerve, and consists entirely of the same 
sized globules connected into fibres, and forming bundles, 
which go off distinctly from the end of the nerve, like rays : 
towards the circumference they almost disappear, and end in 
smooth membrane. 
The whole retina is interwoven with innumerable blood 
vessels, both arteries and veins ; the gelatinous substance 
that holds the globules together, dissolves in water very 
readily ; so that if the parts are soaked in water for three 
or four days with a portion of the optic nerve, they become 
a mass of globules, and the blood vessels, when separated, 
form a beautifully delicate net-work, their branches anas- 
tomosing freely with one another. These appearances are 
represented in PI. II. fig. 4. magnified 400 times. 
By the discovery of this transparent substance, we become 
acquainted with the nature of the medullary structure of the 
nerves ; and can form some idea of their action, which, till 
now, I confess myself to have been totally unacquainted with. 
The nerves, as well as the retina, are composed of this newly 
discovered transparent substance, which is very elastic, and 
soluble in water, and globules of jgVo a °d 4-5 a 0 parts of an 
inch in diameter. Its transparency and solubility account for 
its having remained concealed ; and were it not coagulable, 
in which state it becomes opaque, its existence might even 
now be considered as equivocal. 
Before I say more of this transparent jelly, I will state Mr. 
Bauer's observations on the structure of the brain, of which 
