On the Regulation of Respiration in Reptiles

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Abstract
The effects of various degrees of hypoxia and the combined effects of hypoxia and moderate hypercapnia (2·8% CO2 in the inspired air) have been studied in seven specimens of Lacerta viridis (green lizard) and three of Tarentola mauretanica (gecko). 1. It was found that hypoxia reduces the O2 uptake. 2. Pulmonary ventilation was little changed by hypoxia until the O2% of the inspired air was reduced below 10, when it decreased. 3. A small increase in the ratio (pulmonary ventilation/hr.)/(O2 uptake/hr.) with decreasing O2% was found. When CO2 was added to the O2 mixtures the increase was much greater, indicating an increased sensitivity of the respiratory apparatus towards CO2 during hypoxia. 4. The effect of hypoxia on respiratory frequency was always to cause a decrease. Addition of 2·8% CO2 to the inspired air had little effect. At a body temperature of 20°C. the decrease occurred at O2% in the inspired air below 10, whereas at 30°C. the frequency was higher, but decreased as soon as the O2% was below 20 (room air). 5. It was found that the respiratory frequency in Lacerta varies linearly with the metabolic rate (O2 uptake). 6. The respiratory depth increases with decreasing O2% in the inspired air, at 20°C. below 10% O2 and at 30°C. below 20% O2. Addition of 2·8% CO2 in both cases doubled the respiratory depth at all degrees of hypoxia.

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