A histological study of the colic caeca in the bantam fowl

The caeca of fourteen bantam fowls have been studied. These fowls ranged in age from six days' incubation to three years after hatching. Between the fifth and sixth days of incubation rectal caeca arise as evaginations from the intestine at the junction of the ileum with the colon. The develoing caeca closely resemble histologically the intestine to which they are attached. The caeca are essentially devoid of content until about the nineteenth day of incubation, but during the remaining days of incubation are gorged with a bluish‐gray material similar to that found in the colon. Thus, an early defecatory function is indicated. In general, the proximal third of the caeca remains histologically similar to the intestine, but the distal two‐thirds undergoes regression. The latter involves the atrophy of the epithelium and glands, accompanied by the appearance of lymphoid tissue. Much of the lymphoid tissue eventually disappears, to a large extent by atrophy and dissolution of the leukocytes. However, to some extent, lymphocytes develop into granulocytes which escape with other leukocytes into the lumina of the caeca and there disintegrate. Lymph nodules begin to appear in the caeca about one week after the chick hatches. The leukocytes, at least in part, arise in situ from the reticular stroma. Eosinophils arise in certain areas of the tunica propria, and in the earlier stages of their development resemble large lymphocytes, in the cytoplasm of which basophilic, amphophilic, and acidophilic granules are intermingled.