Reptilian thymus gland: an ultrastructural overview.

Like in higher vertebrates, the thymus gland of reptiles consists of lymphoid cells within epithelial framework and characteristic myoid cells. Mammalian-like Hassall's corpuscles are absent. Secretory cells, secretory and degenerative cysts as well as phagocytic cells, and plasma cells can be observed. Interdigitating cells and some characteristic features of thymic innervation and vascular system are also described in the reptilian thymus gland.