In his book , `` The Mentality of Apes '' , Köhler describes how the apes use their hands , saying `` large , powerful and flexible hands are natural links between himself and the world of things , and he attains the necessary amount of muscular force and co-ordination at an earlier age than the human child '' .
In his book , Köhler describes how the apes use their hands : `` large , powerful and flexible hands are natural links between himself and the world of things , and he attains the necessary amount of muscular force and co-ordination at an earlier age than the human child '' Köhler ( 1925 ) .