The Book of Household Management by Mrs. Beeton

the least is the mode by which their respiration is accomplished. This is effected by means of air-vessels, which extend throughout the body, and adhere to the under-surface of the bones. These, by their motion, force the air through the true lungs, which are very small, and placed in the uppermost part of the chest, and closely braced down to the back and ribs. The lungs, which are never expanded by air, are destined to the sole purpose of oxidizing the blood. In the experiments made by Mr. John Hunter, to discover the use of this general diffusion of air through the bodies of birds, he found that it prevents their respiration from being stopped or interrupted by the rapidity of their motion through a resisting medium. It is well known that, in proportion to celerity of motion, the air becomes resistive; and were it possible for a man to move with the swiftness of a swallow, as he is not provided with an internal construction similar to that of birds, the resistance of the air would soon suffocate him.