18 
Casey A. Wood. 
gutter-like conduit for the purpose of conveying the lachrymal 
fluid in the direction of the puncta. These openings are relatively 
large and always communicate with correspondingly large canaliculi, 
which in the Sparrow are about 2 mm. long. They join to form a 
large fibrous tube, lined with epithelium, the lachrymal duct, that 
runs directly downward and forward toward the median line until 
it opens into the choanal slit, the marginate spines of which direct 
its contents backward into the esophageal opening. 
In the Sparrow a probe 1 mm. in diameter can readily be passed 
through the lachrymal duct and this probably represents the lumen 
of the tube. The canaliculi are about 1 mm. long, while the length 
of the common duct may be set down as 3.6 mm. 
Slonaker and the writer have not been able to demonstrate the 
presence of ciliated epithelium in the duct mucoca. 
The openings analogius to the human puncta are irregularly 
rounded; the upper one being distinctly larger and more patent 
than the lower. Corresponding to these, Slonaker’s peripalpebral 
groove is deeper, longer and better marked at the conjunctival mar- 
gin of the upper lid than at the corresponding border of the lower 
lid. 
The principal facts to be remembered about the lachrymal drain- 
age in Birds are ( 1 ) that the free margin of the third lid is anchor- 
or half-spear-shaped; (2) the free edge probably pushes before 
it — scraper-like — the Harderian fluid, thus cleansing the cornea 
on the contraction of the pyramidalis and quadratus muscles; (3) 
at the instant of rest this same secretion, supplemented or not by 
the lachrymal fluid, is pulled (bucket-like) back and emptied into 
the canaliculi; (4) during the performance of this act it is to be 
remembered that at the end of even the most complete excursions 
of the nictitating membrane the lower edge of the lower lid ad- 
vances only about half a millimetre, while, although there is a 
simultaneous twitching of its palpebral margin, the upper lid ap- 
parently does not come forward at all. 
