四肢解構

both the human hand and foot represent a triumph of complex engineering, exquisitely evolved to perform a range of tasks.
　　Our arms and legs are pentadactyl limbs - they have five digits.
　　When the fist four-legged animals began to move onto the land from the sea around 380 million years ago some had as many as eight digits but the familiar five digit pattern soon became the standard which has since been modified in certain groups such as frogs and birds.
　　Few people except medical students ever get the chance to perform a human dissection.
　　You can learn a lot from books and lectures but it is only by dissecting the human body yourself that you truly understand how it works.
　　In a specially prepared room in Glasgow University, Anatomist Quentin Fogg skilfully dissected a human hand and foot - taking them apart layer by layer to reveal their innermost secrets.
　　The hand is one of the most complex and beautiful pieces of natural engineering in the human body.
　　It gives us a powerful grip but also allows us to manipulate small objects with great precision.
　　This versatility sets us apart from every other creature on the planet.
　　The hand has one of the strangest arrangements of muscles in the body.
　　Through habitual use and training even a single finger can support the entire body weight.
　　Most of its movements are controlled by muscles that aren't located in the hand at all, but in the forearm.
　　The muscles of the forearm connect to the finger bones via long tendons that pass through a flexible wrist.
　　This remote musculature gives the fingers movement and strength that wouldn't be possible if all of the muscles had to be attached directly to them.
　　In effect, the hand is simply a bony puppet, lashed together by ligaments and controlled by the forearm.
　　But that arrangement allows us to do so much. At one extreme is the impressive strength of a climbers' hands.
　　Through habitual use and training even a single finger can support the entire body weight.
　　At the other extreme a concert pianist needs great finesse and this comes from muscles within the hand called intrinsic muscles.
　　Some of these muscles specifically control the thumb and little finger while others such as the lumbricals (named for their worm-like shape) are not directly attached to bones but to tendons and allow wonderful subtlety of movement.
　　Specialised skin
　　No one would doubt that thumb is the most important digit of all. It accounts for 40% of the hand's capabilities and unsurprisingly if you lose one, sur