Tenth Doctor's hand

The Doctor's hand was the severed right hand of the Doctor which he lost shortly after he regenerated into his tenth incarnation.

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During a sword fight with the Sycorax leader on the deck of their ship, the leader slashed the Doctor's right hand off and it fell somewhere in London. Because he was within the first fifteen hours since his regeneration, he was able to regrow the hand. (DW: The Christmas Invasion)

After Captain Jack Harkness travelled from 200,100 to 1869, he eventually found the hand and used it to detect the Doctor whenever he came to the Cardiff Rift to refuel, hoping to find a version of the Doctor which coincided with his own timeline. (DW: Utopia). The precise details of how it detected the presence of The Doctor was not divulged but it's apparent glowing (TW: End of Days) suggests it is similar to the TARDIS key glowing when the TARDIS was approaching (DW: Aliens of London), further suggesting that perhaps the hand detected the presence of the TARDIS instead of The Doctor, or else it may've been detected only the presence of the Tenth Doctor from whom it came, thus allowing Jack to detect a version of The Doctor who had already met him following his regeneration, records of which he may've found on the Torchwood archives, considering that he recognised the Tenth Doctor on sight, claiming to have been "following him" (DW: Utopia). He kept the hand preserved in a jar which he kept on his desk. Despite being severed, it did not decay and continued to move and twitch. (TW: Day One)

When Carys Fletcher escaped, she broke the jar, distracting Jack enough for her to escape. (TW: Day One)


 * However, the container has since been seen to be intact, presumably repaired or replaced by Jack.

When the Doctor arrived on Cardiff Bay, the hand started to react, glowing and moving.(TW: End of Days) After the Doctor came to refuel at the Rift, Captain Jack joined the Doctor and brought the severed hand with him. After travelling to the year 100,000,000,000,000, the Doctor, Martha Jones, and Jack met Professor Yana, who then became the Master. He took the Doctor's hand from Jack and escaped in the Doctor's TARDIS after he regenerated. (DW: Utopia)

The Doctor was able to fix Jack's Vortex Manipulator so they could travel to 2008. When they encountered the Master, he revealed that he put Richard Lazarus' genetic technology into his laser screwdriver. By using the Doctor's biological code he gained from the hand, the Master was able to age the Doctor 100 years. (DW: The Sound of Drums) What followed were the events of The Year That Never Was, after which the Doctor reclaimed his severed hand and kept it aboard his TARDIS in the control room. (DW: Last of the Time Lords)

After the Sontaran invasion of Earth, the TARDIS set off by itself to Messaline, with the hand apparently reacting to Jenny's later birth. (DW: The Poison Sky, The Doctor's Daughter)

The Doctor's hand remained in his TARDIS and was present for the Doctor's apparent regeneration following his being shot by a Dalek. (DW: The Stolen Earth). After the Doctor had healed from the damage caused by the shot, he channelled the excess regenerative energy that would have changed his appearance into a bio-matching receptacle in the form of his hand, thus leaving him healed while remaining in his tenth incarnation. (DW: Journey's End)



However Donna eventually touched the energised hand which caused a Meta-Crisis from which a new version of the Doctor grew. The new Meta-Crisis Doctor had the intelligence of the original Doctor mixed with Donna's persona and attitude. (DW: Journey's End)

Behind the scenes

 * David Tennant did not provide the cast for the hand.
 * Although Journey's End doesn't go into detail, it is possible to speculate based upon the Doctor's statements to Donna, Rose and Jack that he kept the preserved hand in the TARDIS console room (rather than putting it into storage) for very likely the purpose shown in Journey's End as a vessel to stave off a regeneration. Speculatively, had the hand not formed the Meta-Crisis Tenth Doctor or actor constraints not forbidden it, the Tenth Doctor may've been able to use the hand to avoid regeneration indefinetely and, arguably, lived forever.