8 



ON THE BUESA FABRICII IN BIRDS. 



" bursa Fabricii." This third part of the " cloaca" is bounded below by 

 the external sphincter muscles, which often form in birds a great thick 

 fleshy mass ; this chamber, from lodging the penis or clitoris, is deno- 

 minated " loge copulatrice " by M. St.-Ange. In many birds additional 

 glands, opening by large pores, or forming irregular arborescent patches, 

 are developed in the walls of the cloaca in this region. It results there- 

 fore from the above-described disposition of parts that, in its most deve- 

 loped form, a bird's " cloaca " is divided into three chambers communi- 

 cating with each other, and into which open respectively (from above 

 downwards), first the rectum, secondly the urino-genital ducts, thirdly the 

 bursa Eabricii*. This disposition of parts is seen in fig. 1. The bursa 



Fig. 1. 



Cloaca of Chauna derbiana, laid open from before. 



a. Rectum, b. Opening of ureters, b'. Genital papillae, c. Fold of mucous membrane 

 d. "Vesical sphincter " of M. St.-Ange. e. Opening of bursa Fabricii. /.Bursa 

 Fabricii (supposed to be seen through the posterior wall of the cloaca). 



Eabricii, when well developed, consists of a sac-like pouch, usually with 

 thick glandular walls : it is blind above and constricted below, and 



* Prof. Huxley describes it (' Anatomy of Vertebrate Animals,' p. 308) as opening 

 into the " anterior and dorsal region of the cloaca." If " anterior " mean here, as I 

 suppose it does, " anterior " as regards the whole length of the digestive tract, this is 

 an error ; for, as I have above stated, the opening of the bursa is in the lowest chamber 

 of the cloaca (i. e. that nearest the vent), and therefore into the most " posterior " one 

 as regards the general direction of the alimentary canal. 



