Morphologic and Developmental Differences between the Cells of the Chicken’s Thymus and Bursa of Fabricius

Apparent functional differences between the chicken’s thymus and bursa, two lymphoepithelial organs considered similar in many ways, have prompted an evaluation of the morphologic and developmental differences between the cells of these two organs. Thymic lymphocytes are well developed prior to the time of hatching, whereas bursal lymphocytes remain large and possibly relatively immature for the duration of the bursa’s existence. These differences may provide a reasonable explanation for the functional differences observed between the bursa and thymus.