The Thymus in the Chicken and its Anatomical Relationship to the Thyroid

Abstract

The surgical removal of either the bursa of Fabricius or the avian thymus has been used to demonstrate their roles in the immunologic maturation necessary for antibody production (1) or delayed sensitivity (2–6), respectively. The bursa is a discrete organ, readily removed. The thymus of the chicken is composed of several lobes which lie above the jugular vein on either side and occupy almost the entire length of the neck. The most posterior lobe is closely adjacent to the thyroid. The number of thymic lobes on each side has been reported to be five (7), seven (8, 9) or to vary from six to eight (10). We report herein that complete thymectomy of 1-day-old chickens is essentially a surgical impossibility due to the relative positions of the thyroid and posterior lobes of the thymus. Thirty White Leghorn chickens, 10 each at 1 day, 5 weeks and 10 weeks of age, respectively, were killed and the numbers of thymic lobes on side has been reported to be five (7), seven (8,9) or to vary from six to eight (10).