Morphometric study of the avian adrenal gland.

The interrenal and medullary cords as well as the blood vessels and connective tissue proportions in the adrenal glands of the male Nigerian fowl (Gallus domesticus) and guinea-fowl (Numida meleagris) were studied by microstereological techniques. Laying domestic fowl of the Rhode Island Red breed were entirely defeathered and maintained in a hot, humid pen for a period of three months, after which the adrenal glands were also studied microstereologically. Interrenal cord width was also measured in all the birds studied. The interrenal cords of the subscapular zone were consistently wider than those cords in the inner zone of the adrenal glands. This clearly suggested morphological zoning. The proportion of interrenal tissue was significantly greater in the guinea-fowl than in the Nigerian fowl, but the medullary tissue and the blood vessels and connective tissue were not significantly different. Interrenal hypoplasia or medullary hyperplasia occurred in the defeathered Rhode Island Red fowl as compared to the control birds of the same breed and sex. The significance of these findings is discussed.