3 4 & Mr. Home’s Account of an Orifice 
reasons for considering it as the orifice of a lymphatic vessel 
intended to carry off the vitiated parts of the vitreous humour 
and crystalline lens. 
In the human subject, as no examination can be made for 
some considerable time after death, it is impossible to ascertain 
what is the real state of this orifice in the living eye, and what 
changes take place in it after death ; we only learn, that the 
tinge of yellow surrounding the orifice is very slight, when the 
eye is examined recently, and that the next day it becomes 
much deeper. 
These points appear to be satisfactorily cleared up, by the exa- 
mination that was made of the monkey’s eye, as it was begun be- 
fore the parts had lost the appearance belonging to them as living 
parts. In that state, the retina was transparent, and no orifice 
could be seen ; so that the orifice is rendered visible, by remain- 
ing transparent, while the surrounding retina becomes opaque. 
This appears to decide the dispute between Messrs. Soemmering 
and Buzzi ; for, if this part does not undergo the change pe- 
culiar to the retina, we must consider the retina as wanting 
there. After the orifice is thus rendered visible, the yellow tinge 
is wanting, and does not take place for several hours, and even 
then is fainter than it becomes afterwards ; which appears to be 
sufficient evidence, that this tinge is the effect of some change 
after death, and cannot, therefore, have any effect upon vision. 
The orifice has been supposed to account for a small object 
becoming invisible, when placed at a certain distance from the 
eye, and brought opposite a particular part of the retina. This, 
however, cannot be the case, as its situation in the retina does 
not correspond with the part opposed to the object, when ren- 
dered invisible. 
