364 JAMES ROLLIN SLONAKER 



portion. The movement of the free margin of the third eyeUd, 

 therefore, approaches that of a pendulum. This movement is 

 accomplished in the following manner : the contraction of the 

 pyramidalis and quadratus muscles (described elsewhere) drawg 

 the membrane over the eye, at the same time it puts the elastic 

 tissue of the third lid on a stretch. On relaxation of these mus- 

 cles the elastic fibers draw it quickly forward to its resting posi- 

 tion. If smooth muscle fibers are present in this membrane as 

 described by the authors mentioned above, owing to their slow 

 action they can take no part in these extremely rapid movements. 



THE LACRIMAL APPARATUS 



The glands of the eye of the sparrow are two: the lacrimal 

 gland proper and Harder's gland. There is a great difference in 

 the size of these two glands. 



The lacrimal gland is small, triangular, and flat (about 1.25 

 mm. across), and lies closely adjacent to the eyeball, slightly 

 below the equator and temporal to the outer canthus of the eye 

 (fig. 13, Lg). It is abundantly supplied with minute blood- 

 vessels from the external ophthalmic artery and vein. It is 

 innervated mainly by branches from the lacrimal nerve (fig. 27, 

 I) soon after it leaves the inferior orbital branch of the superior 

 maxillary nerve. It also receives some small twigs directly 

 from the inferior orbital nerve. The gland thus lies in the angle 

 formed by the superior orbital, inferior orbital, and lacrimal 

 nerves (figs. 18 and 19, lg). 



Its secretion, which is scanty, enters the conjunctival sac at 

 the lower temporal portion of the lower lid, and is evidently 

 used to lubricate this portion of the lower lid which is not reached 

 by the nictitating membrane. According to Sardemann ('87), 

 a single wide duct leads from this gland to the lower lid. 



Harder's gland is large and irregular in form. It covers 

 almost one-third of the posterior surface of the eye (figs. 15, 17, 

 and 23, Hg), and extends from the region of the optic nerve for- 

 ward as a broad lobular mass, narrowing abruptly to its duct 

 where it passes under the proximal insertion of the superior 

 and inferior oblique muscles. A large dorsal projection is 



