s 
Casey A. Wood. 
by pressing the soft, convoluted marginate rolls into one another. 
The difference between lid closure in the Sparrow and most of the 
higher vertebrates is, roughly speaking, that between a roller-desk 
cover and that of the mouth of a tobacco pouch. 
The movements of one nictitating membrane (or third eyelid) 
is in most birds probably independent of the other, although they 
generally act together. In an adult, male Sparrow, whose cornea 
had been irritated by manipulation, the average nictitations of 
five-minute observations was 55, while in the fellow eye the winking 
was reduced to 47. In a darkened room the number of nictitations 
fell to 41. The extremes of numerous observations under various 
conditions of rest, darkness, bright illumination, after the Bird 
had flown about the room, after irritating the cornea, etc., were 
(during rest) 33, and (during exposure to direct sunlight) 61. 
Under the last named condition, while the nictitating membrane 
was drawn over the globe rapidly and completely, it was returned 
to place very slowly, so that the eye was covered by the membrane 
during a relatively longer period than usual. 
In most Birds, the lids of the Sparrow's eye close immediately 
after or just before death. This, as is well known, is entirely dif- 
ferent in Man and many other Mammalia; and the explanation is 
that the lid-closer is really a smooth, sphincter muscle innervated 
by the sympathetic, which continues to act after the departure of 
consciousness and after the eye-openers (innervated by striped 
muscles) have ceased to be under control of the will. 
The sensory nerve supply to the lid is also entirely different from 
that of Man. Slonaker found that it is from the lachrymal branch 
of the fifth nerve only, which, after giving off branches to the 
lachrymal gland, divides into two portions, one going forward into 
the lower lid and uniting with the superior maxillary nerve. As 
yet unverified is his belief (from dissections of the parts involved) 
that minute branches from what he calls the frontal nerve may 
send sensory branches to the conjunctiva and to the skin about the 
external canthus. 
One of the most interesting organs of the avian eye is the third 
eyelid or nictitating membrane. Fumagalli has furnished an elab- 
orate description ( Internat . Monatschr, f. Anat., 1899, p. 129) of 
the minute anatomy of this membrane, as found in the Hen and 
Pigeon. Slonaker and the writer have not, so far, entirely investi- 
gated the nerve and blood supply of the Sparrow, but agree with 
Fumagalli and other investigators that the nictitating membrane 
