The Testis and Thyroid in a Hen-Feathered Silver-Grey Dorking Cock

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Abstract
A case is described of an apparently normal silver Dorking cock becoming henfeathered. The endocrine glands of this bird were examined, and the testes and thyroid found to be distinctly abnormal. The testes showed large masses of "luteal" cells, encapsuled fibrosed masses, abnormal spermatogenesis and non-functioning tubules. The thyroid showed myxoedematous and cystic conditions with an apparent attempt at compensation in the functioning tubules, and on the whole the appearance of an under-functioning gland. The glands of two fertile Sebright bantams were examined. The testes were normal, without "luteal" cells ; the thyroid was small, relatively rich in connective and poor in glandular tissue, with small secreting vesicles and poor blood supply, suggesting that the Sebright thyroid is subnormal in activity. The evidence suggests that an under-functioning thyroid, either pathologically induced or apparently healthy, may be a controlling factor in hen-feathering, either by acting in combination with the gonad secretion, or by altering it. The hypothesis is put forward that the thyroid and gonad act antagonistically in this respect; and a suggestion is made by which the condition of the plumage may be represented as the algebraic sum of the influence of the two glands.