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Used in copulation; -- said of the external reproductive organs of the males of many animals, and sometimes of those of the females.

timulation; -- as, the condition of an organ of sense, when its nerve is affected by some external body; esp., the act of exciting muscle fibers to contraction, by artificial stimulation; as, the irritation of a motor nerve by electricity; also, the condition of a muscle and nerve, under such stimulation.…

arge veins which return the blood from the head to the heart through two chief trunks, an external and an internal, on each side of the neck; -- called also the jugular vein.

The external margin of the aperture of a shell. See Univalve.

Lying at, or extending toward, the side; away from the mesial plane; external; -- opposed to mesial.

moving uniformly in a straight line, except so far as it is made to change that state by external force. (2) Change of motion is proportional to the impressed force, and takes place in the direction in which the force is impressed. (3) Reaction is always equal and opposite to action, that is to say, the actions of two…

Occupied with, or under the influence of, something, so as to be insensible of external things; as, to be lost in thought. Lost motion (Mach.), the difference between the motion of a driver and that of a follower, due to the yielding of parts or looseness of joints.

Protected by an external coat, or covering, of scales or plates.

External appearance; from. [Obs.] Shak.

he fundamental doctrine of his system is that the mind can not have knowledge of anything external to itself except in its relation to God.

nkle joint. The malleolus of the tibia is the internal projection, that of the fibula the external.

n artistic or skillful manner, in science or art. Manipulation is to the chemist like the external senses to the mind. Whewell.

The external fold, or folds, of the soft, exterior membrane of the body of a mollusk. It usually forms a cavity inclosing the gills. See Illusts. of Buccinum, and Byssus.

ile very immature. The female generally carries the young for some time after birth in an external pouch, or marsupium. Called also Marsupiata.

A natural passage or canal; as, the external auditory meatus. See Illust. of Ear.

cells of the skin (particularly in the skin of the negro), in the epithelial cells of the external layer of the retina (then called fuscin), in the outer layer of the choroid, and elsewhere. It is supposed to be derived from the decomposition of hemoglobin.

A large aquatic American salamander of the genus Necturus, having permanent external gills.

at form of sexual reproduction in which an embryo undergoes a series of marked changes of external form, as the chrysalis stage, pupa stage, etc., in insects. In these intermediate stages sexual reproduction is usually impossible, but they ultimately pass into final and sexually developed forms, from the union of which…

ves to moisten and protect. It covers the lining membranes of all the cavities which open externally, such as those of the mouth, nose, lungs, intestinal canal, urinary passages, etc.

uatic amphibian (Siren lacertina), found in the Southern United States. It has persistent external gills and only the anterior pair of legs. See Siren. -- Mud frog (Zoöl.), a European frog (Pelobates fuscus). -- Mud hen. (Zoöl.) (a) The American coot (Fulica Americana). (b) The clapper rail. -- Mud lark, a person wh…