14 



ON THE BURSA FABRICII IN BIRDS. 



uniappendiculatus) from behind. The bursa is, as one sees, a large, 

 somewhat triangular sac, attached above by a broad riband-like muscle to 

 the posterior wall of the alimentary canal. Most of the back wall of the 

 bursa has been cut away (a), to show the opening into its cavity of the 

 cloacal chamber (6), out of which a pointer (d') is seen passing up into 

 the rectum above through the recto-cloacal valve. Prom this, I think, it 



Fig. 5. 



Vent of young Ernu (Dromceus novce-hollandiM} with the parts still in situ, 



viewed from the outside. 



A. External sphincter. B. Cavity of bursa. C. Wall of cloaca. D. Opening of 

 cloaca into the bursa. E. Clitoris. F. Glandular pores. 



will at once be evident that the cloaca does not open directly to the outer 

 surface, but indirectly through the bursa by means of its large posterior 

 and inferior aperture b. A similar condition of things is seen in fig. 5^ 

 in a young Emu (Dromceus novce-hollandice) where the parts are undis- 

 P. Z. S. 1 877, turbed and in situ, and in fig. 6, in an Ostrich (Struthio camelus, immature 



p. 315. 



female) where the bursa has been nearly all removed to show the pos- 

 terior opening of the cloaca into its cavity, and the communication of 

 the latter with the exterior, as indicated by the direction of the pointer 

 (D D'). The same is the case in the young Nandou (liliea americana). 

 In all these birds the walls of the bursa are thickly glandular ; there are 

 no regular crests and sulci, however, but the glands are arranged in 

 patches, the whole having a honeycomb-like or dendritic appearance. 

 This disposition of parts, however, is not permanent. As the birds grow 

 older, the size of the bursa gradually diminishes and its walls become 

 less glandular; its mouth is no longer equal in extent to the whole 

 width of the outermost chamber, but becomes narrowed ; and finally the 

 whole bursa disappears, its remains becoming lost in the muscles of 

 the back of the cloaca. This state of alrophy of the bursa is represented 



