HANDS. Apart from Mudra Vijnan which point medical benefits of the postures of hand, many other performance which are not medical can be attributed to hand.
Very eloquent. When they are capable of transmitting emotions without uttering a w0rd. Rather they become operative when the words fail to be adequate. They can express love by simple holding other hands. They can reassure by a gentle touch. They can express anger by a blow, They can show exasperation by fluttering. They can accuse by pointing a finger. They can call or send some one by simple waving. They can show win by raising index finger skywards. They can show acceptance and joy by clapping. The list can go on.
Some motions are reflexive like pointing a finger to accuse. Or tapping your forehead in despair. Closing the fist when angry. Open and close the fingers when helpless. Put them on the ears when in shock.
All Indian classic dance use hand postures to narrate. Raising of the thumb of right hand indicates Lord Rama. Rising of index finger as if it is balancing a wheel indicates Lord Krishna, A galloping deer is indicated by touching two middle finger to the thumb and raising end fingers like ears. A fish is shown by putting palm on the palm, closing all fingers except thumbs, which wave as if swimming. Again all these are called as HASTMUDRA for dance.
Benefited with 15 joints including knuckles. 3 each in four fingers and thumb and 1 in the wrist . . They can hold, push, twist, pick, bend, warp, tear and many other things. Therefore supposed to be most efficient machine ever produced.