1877.] BURSA FABRICII IN BIRDS. 315 
and in situ,—and in fig. 6, in an Ostrich (Struthio comelus, imma- 
ture female )—where the bursa has been nearly all removed to show 
the posterior opening of the cloaca into its cavity, and the communi- 
cation 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 Rhea 
americana). In all these birds the walls of the bursa are thickly 

Cloaca and Bursa of young Ostrich (female), viewed from behind. Most of 
the posterior wall of the bursa has been removed. 
A. External sphincter muscle. B. Cut surface of bursa. O. Opening of cloaca 
into bursa. D, D’. Pointer passing from bursa to exterior. 4H, BH. 
Ureters. F. Oviduct. G. Clitoris. H, H’. Pores; beneath them the 
smooth, non-glandular part of the bursa. 
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 gra- 
dually 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 dis- 
appears, its remains becoming lost in the muscles of the back of the 
cloaca. This state of atrophy of the bursa is represented in Casuarius 
picticollis in fig. 7 (p. 316), the only remains of its existence being seen 
in the few irregular circular folds on the mucous membrane at A. 
