Fig. 67 represents the muscles on the back of the forearm. The tendons pass from them, and run, some to the wrist and extend, or bend backwards, the wrist upon the forearm, some to the thumb and extend the several joints ofthe thumb; and others run to the back of the fingers. These leaders lie nearer to the skin than do those on the palmar aspect; and most of those which go to the thumb and fingers may be distinguished through the skin. The short muscles (A, A) situated upon and between the metacarpal bones pass from them to the sides of the fingers; some of these serve to spread the fingers out from one another, while others have the effect of drawing them together. There are several such small muscles on both surfaces of the hand, but I must not detain you by a description of them; and there are other little muscles passing from the flexor tendons to the phalanges, which have been called _fidicinales_, from their assisting in performing the short quick motions of the fingers, and from their being, accordingly, called into action in playing upon the violin and other musical instruments. _Movements of the Thumb._ In its adaptation to the purposes of bearing the weight and ministering to the locomotion of the body the human foot excels that of any other animal; and, unquestionably, the human hand is not less preeminently distinguished by the nicety, the variety, and the freedom of its movements. This is shown by the manner in which it can be twisted about, by the exquisite play of the fingers; and it is shown, above all, by the mode in which the thumb can be moved to and fro, can be opposed to the other fingers, and to any part of them individually and collectively, and can be folded beneath them or clasped upon them as occasion may require. The power which the thumb possesses, and gives to the hand, is signified by its name--“pollex,”--derived from the Latin word _pollere_, which means to have power. Some have supposed that the word “poltroon” is derived from _pollice truncato_, and signifies one so cowardly that he has submitted to have his thumb cut off in order that he may be incapacitated for fighting. The faculty which we possess of moving the thumb in the way I have mentioned, athwart the other fingers, and of touching any part of the palmar surface of either of them depends, partly, upon its being set, not quite in the same plane with them, but, obliquely, so that when it is moved towards the palm it faces or opposes the other fingers; and, partly, upon the nature of the joint between its metacarpal bone and the bone of the wrist with which it is connected.