184 
MR. TOYNBEE ON THE ORGANIZATION AND NUTRITION 
above, extend upon the anterior surface of the capsule. Immediately they reach 
the latter they become straight, run parallel with each other, and are directed 
towards the centre of the anterior surface for the distance of a quarter of a line, when 
they stop in their course, and form looped dilatations, which give origin to small veins, 
Plate XVI. fig. 6. It is most probable that these vessels recede at subsequent periods 
of development, so as to leave the whole of the anterior surface of the capsule 
capable of being permeated by the rays of light*. These vessels, in a diseased state, 
are sometimes prolonged into the whole of the anterior capsule, (or to speak with 
more propriety, the anterior half of the capsule,) where, in morbid specimens, they 
have been injected by Schroeder Van der Kolk. The capsule of the lens is thus 
pervaded by large and numerous ramifications of blood-vessels, which I believe pour 
out upon its inner or lenticular surface a nutrient fluid ; this fluid will immediately 
come in contact ivith the mass of delicate cells described by Schwann as situated be- 
tween the lens and the capsule. 
The mode of nutrition of the crystalline lens may be explained, by supposing that 
the nutrient fluid is received by the cells just alluded to, and conducted to the lens 
(perhaps has its characters changed in its course by the metabolic functions ascribed to 
them by M. Schwann) through which it is diffused. It has been stated, that the pre- 
sence of blood-vessels in the cornea, the anterior half of the capsule of the crystalline 
lens, and in the substance of the lens itself, appears to be incompatible with their 
function of transmitting the rays of light to the retina. Nevertheless large vessels 
ramify on the posterior half of the capsule. The knowledge of the existence of this 
arrangement of vessels led me to perform some experiments with lenses, from which 
I have deduced the fact, that objects (radiating lines, for instance) situated on the 
anterior' surface of the crystalline lens, produce an indistinctness in the image which 
is formed upon the retina; whereas, when these lines exist upon the posterior surface 
of the lens, the image is perfectly clear. 
3. The Vitreous Body or Humour. 
Structure . — The vitreous humour is composed of cellular cavities which are filled 
with a transparent fluid. The membrane of which the walls of these cells are com- 
posed, — the tunic of the vitreous humour, — is very delicate, and is interspersed with 
corpuscles. 
The Vessels of the Vitreous Humour. 
Many anatomists have stated that the arteria centralis retinae, in its course through 
the vitreous humour, gives off minute branches into the substance of the latter ; but 
these branches have never been described ; on the contrary, Muller, who has paid 
* I have hitherto not succeeded in making a complete injection of these vessels in the adult subject, 
t Harrison, Boyer, Cruveilhier, &c. 
