air duct

The ancient conception of the artery as an air-duct gave rise to the derivation from Gr.

Nerve and air duct, therefore, are the essentials; the rest is so much material in reserve for the process of the metamorphosis.

The air-bladder is double, not cellular, with a large air-duct joining the ventral surface of the œsophagus.

Thus the efficiency of fireplaces may be materially increased, the degree depending upon the character of the air duct installed.

But who would think of putting a burglar alarm on an air-duct?