OCR Text |
Show 1877.] BURSA FABRICII IN BIRDS. 309 into the cloaca at the point already indicated. The bursa lies on the posterior wall of the cloaca (to which it is usually attached by a kind ot aponeurosis) in the space between the cloaca and the pelvis. This Fig. 1. Cloaca of Chauna derbiana, laid open from before. a. Bectum. b. Opening of ureters, b'. Genital papilla?, 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). disposition of parts, as seen from behind, is shown in fig. 2 (p. 310), in the common Guillemot. The bursa when laid open frequently contains faecal matter, more or less hard, or m a y be empty. The walls may be thin, as in the Passeres, Parrots, & c , or thick and markedly glandular, as in the Gallince, Herodiones, &c. The bursa is usually constricted below into a narrow peduncle, with a narrow central channel; above, the contained cavity is more considerable but of varying dimensions. Signor Alesi, in the paper already referred to, has described at great length the minute structure of the bursa Fabricii in the common Fowl and some other birds. I must here content myself with giving a brief resume of his conclusions as regards the histological structure of the organ in question. A transverse section of the wall in the neighbourhood of one of the ridges into which, in the Fowl and allied forms, the interior of the bursa is raised shows |