(From abducere, to draw from.) Those muscles are called abductors which draw backwards the moveable parts into which they are inserted; of which there are several in the human body, viz.

1. Abductor auris, called also triceps auris, and retrahens auriculam, bicaudalis muscularis, intricatus musculus, detractor auris; a muscle of the external ear, called by Winslow the posterior musculus auris. It is called triceps, because it has sometimes three beginnings. It is composed of a few fleshy fibres, which arise from the superior and fore part of the apophysis mastoideus, and descend obliquely to their insertion, in the middle of the concha auriculae. It covers the posterior ligament. Dr. Hunter thinks the ear has only two muscles belonging to its external parts that the retrahens auriculam arises from the maminillary process of the temporal bone, and is inserted into the lower external part of the ear, to pull it backward.

2. Abductor digiti minimi manus. Riolan calls it hypothenar. It rises from the os pisiforme of the carpus, runs upward on the inside of the hand, and is inserted into the external side of the little finger, or its first joint. It helps to separate the little finger from the rest, and also to bend it. It is the flexor parvus minimi digiti of Albinus.

3. Abductor digiti minimi pedis. It rises fleshy and tendinous from the semicircular edge of a cavity on the outside of the inferior protuberance of the os calcis; it has another tendinous beginning from the os cuboides, and a third from the upper part of the os metatarsi minimi digiti. It is inserted into the upper part of the first bone of the little toe externally and laterally. It draws the little toe outwards from that next to it.

4. Abductor indicis. It arises fleshy by two heads from the metacarpal bone of the fore finger, and the first bone of the thumb, and is inserted by its tendon into the basis, or first joint of the fore-finger, laterally-next the thumb. It brings the fore-finger from the middle-finger, and near to the thumb. Cowper calls it adductor pollicis. Douglas says, its use is to bring the index towards the thumb; whence, in respect of this, it may be styled adductor; and,in respect of that, abductor.

5. Abductor occuli, called also indignatorius, or the scornful muscle; musculus exterior; also,abducens, iracundus, and rectus externus. It rises tendinous and fleshy from the foramen lacerum, without the orbit. It is inserted by a thin tendon into the sclerotis, on that side next the nose. It moves the eye towards the little angle.

6. Abductor pollicis manus, called also thenar by Riolan; and abductor brevis pollicis manus, by Albinus. It rises by a broad, tendinous, and fleshy beginning, from the inner part of the traversa ligament of the carpus, and from one of its bones which articulates with the thumb, and is inserted tendinous into the second joint of the thumb. It draws the thumb from the fingers.

7. Abductor pollicis pedis, called also thenar. It rises fleshy from the inside of the os calcis, and tendinous from the os naviculare, and forms a strong tendon, which is inserted at the inner part of the first bone of the great toe, upon its sesamoid bone. It pulls the great toe from the rest. It often has a tendinous origin from the edge of the os cymbiforme, receiving near this bone some tendinous filaments from the tibialis anticus. These two muscles, No. 6, 7, are called Thenar, because they make part of the Thenar.