in the Retina of the Eye. ' 34,1 
made into the vitreous humour, by removing a portion of the 
ciliary processes along with the iris, the tube was distinctly 
seen. The weight of the lens probably pulled forward the vi- 
treous humour, and kept the short tube erect, in its natural 
situation. 
I mention this circumstance, to prevent, as much as I am 
able, other anatomists from being disappointed in not finding 
it ; which may readily happen, if the search be not made with 
considerable attention. 
In the sheep, there is no appearance of a zone surrounding 
the tube. 
These facts, although few in number, are sufficient to prove, 
that this orifice is not peculiar to the retina of the human eye ; 
and that its situation in man and in the monkey is the same : in 
them, it is placed at some distance from the optic nerve ; but, 
in some other animals, its situation is close to that nerve, and 
it puts on the appearance of a tube, instead of an orifice. 
There is one circumstance which is curious, and which it 
will require further information upon this subject to explain ; 
the yellow zone, found in the human eye and that of the mon- 
key, is not met with in any other animal which I have exa- 
mined. 
Having stated the facts, and also the opinions of other ana- 
tomists, that have come to my knowledge, as well as my own 
observations, upon this orifice in the retina of the human eye, 
discovered by Mr. Soemmering, and having added to these, 
several new facts respecting it in other animals, I shall draw 
some general conclusions from the whole, with a view to show 
that the conjectures which have been made, respecting its use, 
are probably erroneous. I shall afterwards point out several 
