This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
As has already been stated, the hand is the essential part of the upper extremity, and mobility is its main characteristic. It terminates in five digits which possess a bony support or framework. In order that the fingers may perform their many complicated movements numerous joints are inserted which necessitate a still greater number of bones. The movements of the hand and fingers are accomplished not only by the long flexors and extensors of the fingers and the flexors and extensors of the carpus, which, as has already been shown, come down from the forearm, but in addition by numerous short muscles situated in the hand itself. An especial peculiarity of the human hand is the ability to oppose the thumb to the other digits.
Fig. 360. - Anterior view of the bones of the carpus and metacarpus, showing insertion of the two carpal flexor muscles.