The histology of the adrenal gland was studied in the females of adult Egyptian heron, Ardeola ibis ibis. Also, the present study declares the similiarity between the histology of the adrenal glands of both two birds, the heron, Ardeola ibis ibis, and the pelican, Pelecnus accidentalis.
In the heron, the left gland is mainly connected with the tunica albuginea of the left ovary while the right gland is closely related to the right kidney since the right ovary is missing. Two types of cells, chromaffin and interrenal cells, are mixed in the internal regions of the gland, while they constitute two layers of chromaffin and interrenal cells, just a capsular region. Outside this region, there are a few groups of sympathetic ganglion cells. The glands are richly supplied with blood spaces.