> The mammalian lung has reciprocating ventilation with large terminal air spaces (alveoli) while the avian lung has a flow-through system with small air capill

> The mammalian lung has reciprocating ventilation with large terminal air spaces (alveoli) while the avian lung has a flow-through system with small air capillaries. As a result the environment of the pulmonary capillaries is very different between the mammals and birds.[1] [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2681264/#:~:text=The%20mammalian%20lung%20has%20reciprocating,between%20the%20mammals%20and%20birds https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2681264/#:~:tex....