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This paper describes a three-fingered nine-degrees-of-freedom hand whose parts can be inserted through trocars and assembled inside the abdominal cavity. Unlike other studies of surgery robots, this study focuses on a nondominant hand of a surgeon and its goal is to develop a robotic hand that can carry out assistive tasks for surgery, as if the human nondominant hand existed in the abdominal cavity. Another advantage of such a robotic hand is that it can grasp and retract large internal organs. The assemblage of the developed hand consists of center, right, and left finger units. The center finger unit is inserted through one trocar, and the right and left finger units are inserted through another trocar and then passed through the trocar, where the center finger unit is inserted. Then, the three finger units are connected to form the hand. One notable advantage of this assembly procedure is that the power transmission used to drive the finger joints is connected outside the abdominal cavity, which makes assembly and disassembly much easier and safer than the previously proposed hand. Although the hand has no wrist, its three finger joints play the role of a wrist joint. In vivo experiments demonstrate that the assembly procedure is simple, and that the hand can be made to grasp, hold up, and retract large internal organs, such as small intestine and spleen, by manipulating its joints in such a way that the hand fits the shape of the organ.