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Notes: The cloacal bursa (bursa of Fabricius) in the guinea fowls appeared either as an oval blind sac with a short thick stalk in one group or had a pointed cranial blind end with a slightly bulging middle part that was followed by a thick caudal stalk in the other group. Both groups of bursae originated from the proctodeal wall of the cloaca and were placed dorsal to the rectum. The average length of the bursa was 18 mm while the average width at die mid section was 15 mm. The internal surface showed about 12 – 14 primary folds.Histologically, the outline of the bursa was well established by day 18 of incubation. The primary folds had also been formed. Lymphocytes had already been encountered within the framework of the bursa at this day. The epithelium bordering the tunica propria was composed principally of two layers of cuboidal cells. Epithelial buds had also formed and some were already detached from the epithelial lining. The blood vessels present were positioned just beneath the outer covering.At day 19 of incubation, most of the epithelial buds had two layers of cells arranged in a circumscribed manner while a few had three layers of cells. Blood vessels had increased in number and were deeper placed inside the bursa than previously.At day 20, the cells of the upper layer of the epithelium were dorsoventrally flattened and stained paler than the cells of the lower layer. It was possible to distinguish the cortex from the medulla and the basement lining between both zones was distinct. Tiny vesicles within the cytoplasm of the epithelial cells at the mucosa and follicles were observed. Macrophges were also observed within the gland.At day 21, blood vessels were observed in the cortex of the follicles. The maximum number of primary folds (14) had been formed.At day 22, serveral follicles had severed connections with the mucosal epithelium. The mucosal lining had dropped to a single layer of cells in some areas. Goblet cells were observed amongst the mucosal cells. A plasma cell had first appeared.By day 25, dead cells had increased quite in number and there was also an increase in number of medium and small-sized lymphocytes within the gland.By day 26, the upper layer of the surface epithelium was composed primarily of tall columnar cells with numerous large vacuoles. Macrophages had suddenly increased within the thin interfollicu-lar spaces and most of them were crowded internally with various sizes of debris.By day one post-hatch, each fold was completely filled with follicles that were separated by thin connective tissue strands.

Notes: The thymus gland of the guinea fowl appeared as a series of pink, irregular-shaped lobes along the jugular veins. These lobes were 13 in number with seven on the right and six on the left side. The third and sixth lobes on the right side were the largest. The largest lobe measured about 20.0 × 5.0 mm while the smallest measured about 5.0 × 4,0 mm.Histologically, it was encircled by a thin layer of poorly stained connective tissue from which strands penetrated the thymic tissue giving incomplete lobules peripherally as early as day 18 of incubation. Lymphocytes and reticular epithelial cells were the two types of cells occurring at this time. Reticular epithelial cells were observed to be vacuolated especially towards the centre of the gland.Macrophages were observed in the thymus on day 20 of incubation for the first time. The blood vessels had accompanied the interlobular septa into the thymus.By day 21 of incubation, blood vessels had actually penetrated the thymic tissue but most of these vessels were of the capillary size. The cortex also became quite distinct from the medulla.At day 22, vacuolation ceased to appear in the cells at the cortical zone. Macrophages were still less than 10 in the slide.At day 23, most blood vessels were within the medulla and they displayed compressed lumi-na. Mitotic figures became a common site amongst the large lymphocytes and reticular epithelial cells.By day one post-hatch, lobulation of the thymus was still poor and macrophages became difficult to identify. The small and medium lymphocytes had outnumbered the large lymphocytes throughout the thymic tissue except at the most peripheral zone of the cortex. Fine vacuoles had reappeared within the cytoplasm of the reticular epithelial cells in the cortex.By day five, the distribution of blood vessels was almost uniform between the cortex and medulla.At three weeks post-hatch, plasma cells and red blood cells were seen in the stroma of the gland for the first time and most of the red blood cells occurred in the medulla.