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The total gonadotrophic activities of the anterior pituitary glands and blood plasma of hens, Gallus domesticus, during the moulting period were estimated using the assay method based on the weight increase of chick testis. The activities in both the pituitary and the blood of hens in the four groups classified according to the progress of moult were significantly higher than those of laying hens. Nevertheless, no detectable level of serum vitellin and a completely regressed ovary were found in moulting hens.Anterior pituitary glands of moulting and laying hens were assayed for their fsh and lh activities by the use of the hcg augmentation method or the ovarian ascorbic acid depletion test. The fsh activity of the moulting hen was about twofold higher than that of the laying hen, whereas lh activity was about equal during the moulting and the laying periods.The serum vitellin of moulting hens increased steeply with the injection of oestrogen over 3 days. When chicken anterior pituitary homogenate was injected once daily for 6 days to hens in the moulting period, a satisfactory follicular growth as in the laying hen was induced in all of the treated hens. Injection of pmsg into moulting hens for 6 days resulted in an increase of serum vitellin in all the hens and the formation of yellow follicles in 40% of the treated hens.These results suggested that the failure of follicular growth in the moulting hen, despite high levels of total gonadotrophic activity in both pituitary and blood, might be due to an unbalanced secretion of endogenous gonadotrophins.

One of the major problems in studies on gonadotropin(GTH)is to use the appropriate assay method. While numerous methods of bio-assay for GTH were used by many workers, one of those was based on the weight-increases of gonad and accessory sexual organ of assay animals, and this might be classified into following three groups according to the species of assay animals;rat, mouse and chick method. Greep et al.(1936)and Cartland and Nelson(1938)concluded that gonads and accessory organs of immature rats suited to assay end-point for GTH. The method in which immature mice were used as assay animal was established by Levin and Tyndale(1937). Breneman(1936, 1945a)indicated that small amounts of anterior pituitary principle would elicit the increase of testicular weight of chicks which were kept without food and water for a test period of 96 hrs. When the

We have found that the concentration of citric acid in the isthmus is not altered in birds injected with fluoroacetate, and the enzymes of the Krebs cycle which seem most likely to be implicated in the high citric acid content of this region are under invel!ltigation.The tubular region of the uterus adjacent to the isthmus, the isthmo-uterine junction•, is considerably richer in calcium and citric acid than the thick muscular region where the main process of shell calcification occurs, and this may be due to the fact that the transition from isthmus to uterus is gradual, there being no definite histological boundary between the two regions 7 • Magnesium forms a complex ion with citrate• similar to that formed between calcium and citrate ; but in spite of the large variations in citric acid in the different segments, the magnesium content of the isthmus and uterus is constant at a level of 15-20 mgm. /100 gm. The magnum, however, which is relatively low in citric acid (less than 10 mgm./100 gm.) contains approximately twice as much magnesium (38 mgm./100 gm.) as any other region of the oviduct.We wish to thank Dr. B. C. Saunders for a generous gift of sodium fluoroacetate.

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