75 
Orifices found in certain poisonous Snakes, &c. 
Another peculiarity is remarkable in snakes furnished with 
the bags described above, namely, an oval cavity, situated be- 
tween the bag and the eye, the opening into which is within the 
inner angle of the eyelid, and directed towards the cornea. In 
this opening there are two rows of projections, which appear to 
form an orifice, capable of dilatation and contraction. From the 
situation of these oval cavities, they must be considered as reser- 
voirs for a fluid, which is occasionally to be spread over the cornea; 
and they may be filled by the falling of the dew, or the moisture 
shaken off from the grass through which the snake passes. 
This apparatus in the snake, has that position which is best 
adapted to pour out the fluid upon the cornea, when the head of 
the snake is erect. 
Dr. Tyson had superficially observed the apparatus which 
has been described, and considered it as a membrana nictitans. 
He says, “ inwards it seemed to have a membrana nictitans, 
“ which removes any dust that might adhere to the eye 
As snakes in general have no apparatus to wash the cornea, 
these particular species must have some peculiarities in their 
mode of life, with which we are not at present acquainted. 
* Phil. Trans. Vol. XIII. p. 27. 
