146 DR. COBBOLD ON THE EYE OF THE COD-FISH. 
the densely laminated character of its substance have proved erro- 
neous, and that the numerous layers which his beautiful prepara- 
tions of the vitreous body showed were only due to the coagulating 
agency of the strong chromic-acid solutions in which the eyeballs 
had been kept immersed before the sections were made. At a meet- 
ing of the Physiological Society of Edinburgh in 1851, I took oeca- 
sion, in Dr. Hannover’s presence, to point out this circumstance, 
and also adduced other evidences to show the erroneousness of his 
conclusions. The well-known fact, that by puncturing the vitreous 
mass in a fresh state we can draw off, as it were, the great bulk 
of its fluid contents, is sufficient in itself to demonstrate that the 
vitreous body is not made up of membranous laminz ;_ but, at the 
same time, there can be no doubt, as my own investigations have 
shown, that the inner layer of the hyaloid tunic sends off a few 
prolongations into the substance of the vitreous mass. Probably 
these extensions form the walls of enormously enlarged cells ; but 
this is a point which I have not been able to determine. 
The principal points, however, to which I now wish to draw 
attention are such as have reference to the occurrence of parasitic 
formations within the cartilaginous matrix of the sclerotic coat, 
to the structure and functions of the so-called choroid gland, and 
more particularly to certain artificially produced phenomena in 
connexion with the large and remarkable twin-cones of the retina. 
The views which I shall here subscribe in regard to the nature of 
the choroid gland are directly at variance with the commonly 
received opinions, and offer, I think, an intelligible explanation in 
regard to a singularly obscure subject. 
(1.) If the external fibrous and internal separable layers be de- 
tached from the true cartilaginous matrix of the sclerotic of the Cod, 
it will frequently be observed, in large eyes at least, that the latter 
contains within it certain oval, rounded, and more or less stellate- 
looking bodies of a dense, milk-white colour. Their size varies from 
that of a pin’s head to that of a pea; and when submitted to high 
magnifying powers, they are found to contain a multitude of minute 
cellules, which have an average individual measurement of about: 
the zj5,th ofan inch. All of them are oval in shape, and contain 
double nuclei, placed side by side at one end of the cell-cavity, 
which also contains a pale-yellow-coloured fluid surrounding the: 
nuclei. So far as I am aware, these bodies have never been de- 
scribed by observers in this country ; but they are manifestly the 
so-called psorospermie, which have been carefully investigated on 
the continent by Miller, Dujardin, Creplin, and others. The 

