In the battle between the third hokage and Orochimaru, hokage summons "God of Dead" to kill (eat ) Orochimaru's soul.. but because he did not have chakra left, so he only can "eat" the arm (so he could not use any Ninja Technique)....

<skip in the middle>

Orochimaru after transfer his soul in a new body, it seems he can move his arm...

How come? I think Orochimaru lose a part of his soul (arm)... which is belong to the soul, not the body.... how can he "heal" his soul after transfer a new container?