in the Retina of the Eye. 
345 
Fig. 4. A transverse section of the eye of a bullock, to show 
that there is a semi-transparent tube projecting from the edge 
of the entrance of the optic nerve, into the vitreous humour. 
This tube is surrounded by a zone, with a distinct margin : it 
is situated on the temporal side of the optic nerve. 
Fig. 5. A transverse section of the eye of a sheep, to show 
that there is a similar tube as in the bullock, in the same situa- 
tion, but much shorter, and without the surrounding zone. 
Yy 
MDCCXCVIII. 
