In mammals there is an inverse relationship between plasma Pco₂ and level of blood lactate and pyruvate (1–3). A similar relationship for an avian species has not been established.

Materials and methods. Adult male white Leghorn chickens (2.5 kg to 3.1 kg) kept in outdoor pens were used in these experiments. Experiments were conducted between February and May so the animals were adapted to cold. The tracheas, left carotid arteries and right brachial veins were can-nulated under local anesthesia (ethyl ch-loride). Incisions were closed and 20 mg/animal of heparin (sodium) was administered intravenously. After waiting approximately 15 minutes, a control sample of blood was drawn. Succinylcholine was injected i.v., initially in a dose of 40 mg/animal and before each additional ventilating regimen in a dose of 20 mg/animal. The animals were over-ventilated artificially by connecting the tracheal cannula of the animal to a respiratory pump which ran at a stroke volume of 38 ml and a rate of 50 breaths per minute (1.9 1/min). Gas mixtures of 21% O₂, and 0, 5 or 10% CO₂ with the remainder as N₂ were delivered to the animals on the over ventilation regimen. Presentation of gas mixtures was randomized to eliminate the possibility of sequence of presentation influencing the results. In some experiments only 0 and 5% CO₂ were used.

At the end of 30 minutes on a given gas mixture a 4 ml sample of arterial blood was drawn after first drawing 1/2 ml to clear the cannula. The portion of blood sample to be analyzed for lactate and pyruvate and glucose was drawn into a 2 ml syringe, transferred directly into a centrifuge tube containing 2 ml of chilled 10% trichloroacetic acid and mixed.