Vertebrata; or Vertebrate Animals. The highest division of the animal kingdom, so called from the presence in most cases of a back-bone composed of numerous joints or vertebræ, which constitutes the center of the skeleton, and at the same time supports and protects the central parts of the nervous system.

Vesicle. A bladder-like vessel; a membranous cavity; a cyst; a cell; especially (a) (Bot.) a small bladder-like body in the substance of a vegetable, or upon the surface of a leaf.—Gray. (b) (Med.) A small orbicular elevation of the cuticle containing lymph, and succeeded by a scurf or laminated scab; also, any small cavity or sac in the human body; as the umbilical vesicle.

Vortices (verto, to turn). 1. A whirling or circular motion of any fluid, usually of water, forming a kind of cavity in the center of the circle, and in some instances drawing in water or absorbing other things; a whirlpool.

2. A whirling of the air; a whirlwind.

3. (Cartesian system.) A supposed collection of particles of very subtile matter, endowed with a rapid rotary motion around an axis. By means of these vortices Descartes attempted to account for the formation of the universe.

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