40 
Structure of the 
[Monthly Microscopical 
Journal, July 1, 1869. 
in which this takes place has never been explained. As the aque- 
ous humour and the ordinary fluid of the vitreous humour contain 
only a fractional part of formative material, which, moreover, is 
entirely destitute of organization, the transudation of these fluids 
through the capsule, in sufiicient quantity to be of any service in 
the nutrition of the fully-formed lens, would, from the experience 
we possess of its nature, tend to its disorganization and opacity 
rather than its nourishment and transparency. Indeed, the capsule 
of the lens possesses a power which, whether vital or elastic, pre- 
vents the transudation of watery fluid through its walls during life 
■ — a power which it loses soon after death, and then it allows ingress 
to the fluid humours of the eye. The same force confers upon it an 
elective affinity by which it is enabled to take up the small amount 
of albumen dissolved in the aqueous and vitreous humours ; and, 
therefore, the anterior capsule is probably also concerned to a small 
extent in the nutrition of the lens. But considering the facts 
already sta.ted as to the close relationship of the vitreous body and 
lens, coupled with the additional fact that the anterior capsule is 
four or five times thicker than the posterior, we must regard the - 
vitreous humour as the reservoir of its nutritive supply. The 
plastic substance which I have described as adhering to the vitreous 
tissue in the form of globules is the only compound which the 
vitreous humour contains capable of undertaking this office, for 
which it seems well suited in every respect. Its immiscibility in 
the ordinary fluid of the vitreous humour enables it to be conveyed 
to the lens in a concentrated state, ready to be received as nutri- 
ment by the latter; its plasticity and higher degree of vitality 
than the ordinary vitreous fluid give it a greater vital and physical 
attraction for the capsule ; while its identity in chemical and phy- 
sical properties to the fluid that pre-exists in the cells of the 
crystalline lens makes it as nearly as possible a certainty that it is 
the pabulum of that body. As the pearly globules have no proper 
cell-wall, and are not confined to tubes, the onward movement of 
these to the lens as the latter has a demand for them must be 
mainly owing to that vital attraction which everywhere exists 
between pabulum and tissue, and which in the body generally exerts 
so much influence on the onward movement of the blood in the 
capillaries. In the present case, however, the elasticity of the fibres 
on which the globules are strung, as well as the tension of the 
humour generally, will combine with the vital attraction to give 
these globules an onward movement corresponding to the direction 
of the fibres, which is centripetal, or that towards the lens. Thus 
the crystalhne lens of the eye is supplied with transparent nutri- 
ment for the repair of its waste by a simple and highly eligible 
process. It demands its nutriment in a state of concentration and 
m a high degree of transparency. The colourless elements of the 
