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Are very minute, and rise from the arterial capillary system. They are situate in every tissue of the body, and on the surface of the mucous and serous membranes and skin; on which each pours its particular fluid. Bichat distinguished three sets. 1. The external, terminating on the mucous and external dermoid system, where they pour the matter of perspiration. 2. The internal, com­prising those of the areolar and medullary tissues, and of synovial surfaces; and, 3. The nutritive exhalants, which vary in each organ where they are found, and preside over the phenomena of composition and increase of every part of the body. The exhalants are the antagonists of the absorbents. They are imaginary vessels, inasmuch as they cannot be detected.