The three _Interossei Interni_, and the three _Externi_, are situated between the four Bones of the _Metacarpium_, as well on the inside of the Hand as without: They have their beginning in the Intervals or Spaces between the Bones of the _Metacarpium_, are united with the _Lumbrical_, and fixt in the last Articulation of the Bones of the Fingers, to produce the Motion of drawing back or removing from the Thumb. The Thumb is mov'd by five particular Muscles; one whereof serves to bend it, two to extend it, one to remove it from the Fingers, and another to draw it to them. The _Flexor_ of the Thumb takes its rise from the upper and inner part of the _Radius_, passes under the _Annular_ Ligament, as also under the _Thenar_, and adheres to the first and second Bones of the same Thumb to bend it. The two _Extensors_ of the Thumb are the _Longior_ and the _Brevior_: The former proceeding from the upper and outward part of the _Cubitus_, ascends above the _Radius_, and is ty'd with a forked _Tendon_ to the second Bone of the Thumb. The _Brevior_ hath the same Origin with the _Longior_, keeps the same Track, passes under the _Annular_ Ligament, and is terminated in the third Thumb-Bone. {47} The _Thenar_ removes the Thumb from the Fingers, and forms that part which is call'd the _Mount of Venus_: It hath its Source in the first Bone of the _Carpus_ or Wrist, and the _Annular_ Ligament, and is inserted in its second Bone. The _Antithenar_ draws the Thumb to the other Fingers, having its Origine in the Bone of the _Metacarpus_, that stayeth the middle Finger, and its Insertion is in the first Bone of the Thumb. The Muscle which serves to extend the Fore-Finger, is call'd _Indicator_: It proceeds from the middle and outer part of the _Cubitus_, and is fixt by a double _Tendon_ in the second Articulation of the Fore-Finger, as also in the _Tendon_ of the great _Extensor_ of the Fingers. That which draws the Fore-Finger to the Thumb is term'd _Adductor_: It commenceth in the fore-part of the first Thumb-Bone, and is terminated in the Bones of the Fore-Finger. That which removes the Fore-Finger from the Thumb is known by the Name of _Abductor_, which arising out of the external and middle part of the Bone of the Elbow, and passing under the _Annular_ Ligament, cleaves to the Lateral and outward part of the Bones of the Fore-Finger. The Little-Finger hath two proper Muscles, _viz._ an _Extensor_ and an _Abductor_. The _Extensor_ springs from the lower part of the _Condylus_ of the Arm-Bone, and is fasten'd by a double _Tendon_ in the second Articulation of the Little-Finger, and in the _Tendon_ of the _Extensor_ of all the others. {48} The _Abductor_, call'd also _Hypothenar_, hath its beginning in the small Bone of the Wrist, which is situated over the others, and is terminated in the first Bone of the Little-Finger on the outside. * * * * * CHAP. XI. _Of the Muscles of the Thighs, Legs, and Feet._