Adrenaline in bird brain.

1. Catecholamine estimations were made on the whole diencephalon and on the hypothalamus of pigeons and fowls using fluorimetry of the acetylated amines as one, and bio-assay after chromatographic separation of the amines as a second method.2. There was no significant difference between the results obtained by the two methods; for pigeons mean percentage methylation was 10% with one and 12% with the other technique, and in the Rhode Island Red breed of fowls the corresponding figures were 28 and 31%.3. The percentage methylation for the hypothalamus of another breed of fowls (Plymouth Rock) was the same as in Rhode Island Red, but it was significantly lower in White Leghorn birds.4. Between the ages of 3.5 weeks and maturity the percent methylation remained unchanged.5. There is no evidence to suggest that bio-assay of adrenaline as used in this and previous work lacks specificity, but differences between avian breeds exist and have to be reckoned with.