THE EYELIDS AND LACHRYMAL APPARATUS OF 
BIRDS. 
Casey A. Wood, M. D., 
CHICAGO. 
Illustrated. 
The arrangement by which the anterior surface of the eyeball of 
Birds is cleansed and otherwise protected from various forms of 
injury differs materially from that which one finds in other verte- 
brates. Even to those who are not specially interested in compara- 
tive anatomy and physiology it offers many points of contact with 
human ophthalmology, and this is the writer’s chief excuse for this 
article. Most of the investigations that form the basis of this paper 
were made in the physiological laboratories of Stanford Univers- 
ity, in conjunction especially with Professor Slonaker. The results 
of these researches were first reported to the Ophthalmological Con- 
gress at Oxford in July, 1914, and published in the American En- 
cyclopedia of Ophthalmology , to whose publisher the writer is in- 
debted for the illustrations. 
That one may appreciate the part played by the eyelids and the 
lachrymal apparatus in the vision of birds it is essential not only 
that the secretion and removal of the tears should be studied but 
that the disposition of the bulbar and palpebral muscles should be 
borne in mind. 
The epidermis covering the avian eyelids is more horny than in 
man. It is attached to the corium by delicate fibres. 
The tarsal plate of the lower lid is composed of closely packed 
connective-tissue fibres, in which one occasionally finds spindle- 
shaped or round cells ; but none of these can properly be described 
as cartilage cells. A delicate network of vessels surrounds the tar- 
sal plate. 
In some birds a fatty layer, more or less marked, is found in a 
well-defined space between the lid edge and the upper margin of 
the tarsus. 
The occompanying illustration shows the lid margins of the 
Sparrow to be composed of about 34 (17 in each lid) deeply pig- 
( REPRINTED FROM OPHTHALMOLOGY, JULY, 1915) 
