318 JAMES ROLLIN SLONAKER 



THE LACRIMAL GLANDS 



The lacrimal secretion in the bird is supplied by two glands, 

 the lacrimal gland and Harder's gland, each of which is con- 

 nected with the conjunctival sac by a single duct (Sardemann, 

 '87). The lacrimal gland, which is smaller, is located in the 

 orbit slightly below and temporal to the posterior canthus. Its 

 secretion is directed onto the temporal portion of the lower lid. 

 Harder's gland is a large, tubular gland (]\IacLeod, '80), located 

 back of the eyeball and covers about one-third of its posterior 

 surface. Its duct opens into the bottom of the conjunctival sac 

 formed by the nictitating membrane and the eyeball. Since 

 the conjunctival surface in the bird is kept moist and clean 

 principally by the nictitating membrane, this portion of the eye 

 would naturally need the greatest amount of lacrimal secretion 

 which accounts for the large size of the harderian gland. 



The lacrimal glands are developed from the conjunctival 

 epithelium (Keibel and Elze, '08; Speciale-Cirincione, '08; 

 Hertwig, '90). They first consist of buds of epithehal cells 

 from the conjunctival sac which grow backward from the regions 

 which later mark the outlets of the ducts from these glands. 

 In the bird a single bud, which is destined to form the lacrimal 

 gland Ues at the temporal canthus; that which will form the 

 harderian gland arises from the pocket under the nictitating 

 membrane. In man the lacrimal gland is formed by a number 

 of buds or solid projections of epithelial cells which start about 

 the seventieth day of development. In the sparrow a single 

 bud is formed and grows backward as a solid, cylindrical mass of 

 cells just outside of, and parallel to, the surface of the eyeball. 

 When it reaches the normal location of the gland it branches 

 into a number of lobes. The first appearance of this gland was 

 seen in the sparrow about the eighth day of incubation. This 

 backward growth is rapid. By the ninth day, lobes of the 

 lacrimal gland are observed. They consist of fairly definite 

 arrangement of cells which, in cross-section, form almost a 

 circle. The cells forming the outer wall are of uniform size 

 and enclose other cells to make a compact mass. The location 



