Airbed

A sack, in the shape of a mattre , divided into a number of air-tight compartments, a projection at one end forming the bolster. Each compartment is provided with a valve, and can be inflated with air by means of a bellows. They are generally made of vulcanized India-rubber. Their advantages are coolne , elasticity, and portability; and they are especially valuable to invalids. Air-cushions are conveniences of similar construction as air-beds, but le complicated, and cheaper. Air-bladder, n. ( Physiol.) A peculiar organ with which the great majority of fishes are provided, and by which they are enabled to adapt the specific gravity of their bodies to the various pre ures of the superincumbent water at different depths. It serves as a receptacle for a certain quantity of air, by the increase or decrease which the alteration in the animal's weight, compared with that of the surrounding fluid, is accomplished. The Te el itself is composed of a lengthened sack, sometimes