Comparative Studies of Histological Structures between the GALT of the Rabbits and the Bursa of Fabricius of the Chickens

As a preliminary experiment for the study of bursa equivalent organs in mammalian the present experiment made a comparison in the development and the histological structures between the GALT (gut-associated lymphoid tissues) of neonatal rabbits and the bursa of Fabricius of chickens. Animals of various ages (from 1st day to 180th day after birth) were sacrificed under the deep anesthesia. The palatine tonsil, Peyer's patch, appendix, and sacculus rotundus from the rabbits and the bursa of Fabricius from the chickens were removed. The serial paraffin sections were carried out for the staining with methyl-green pyronin, PAS, Masson's trichrome, silver, and hematoxylin-eosin. The earliest lymphatic nodules were observed at first in the lamina propria of the GALT from the 7 days old rabbits. On the other hand, only the diffuse lymphatic tissues were recognized in the same portion of the GALT from the 1 day and 4 days old rabbits. Modes of the nodular development in the bursa of the chickens were different from that of the GALT, that is, 'the medullary portion of the nodule were already formed in the lamina propria on the 1st day after hatch and the cortical substances were gradually added around the preformed medulla in the 4 days old chickens. The undifferentiated basalepitheloid cell layer of the nodules of the bursa were continuous to the surface epithelium of the bursa. Both nodules of the GALT and the bursa contained lymphocytes, blast-form cell and dividing cells in it. No diffuse lymphatic tissues in the extrafollicular areas of the bursa of Fabricius were observed, while there are diffuse lymphatic tissues which include the vessels covered with the simple cuboid epithelium in the extrafollicular areas of GALT. The diffuse lymphatic tissues of the extrafollicular areas of the palatine tonsils are more well-developed than those of the Peyer's patch, appendix, and sacculus rotundus. The results of the above findings suggested that the origin of the nodules in the bursa differs from the nodules of the GALT. The former may be entodermal origin and the latter mesenchymal origin