The time at which the fœtal thyroid and pituitary glands in sheep and oxen can be shown to contain secretory products as inferred by their action upon amphibian development and colour response conforms to what might be anticipated on histological grounds: neither experimental nor microscopic data provide any justification for attributing the ætiological significance of the monstrous abortive Dexter calf to thyroid deficiency. Preliminary experiments suggest the desirability of using the embryo chick for studying the correspondence between secretory activity and histological structure in the case of the adrenals.

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