a lateral direction transverse to the pivot axis of the body elements with respect to each other as is seen in fig9 each of the body elements has two such conical recesses and two holes and there are two flexible connectors extending down the length of the body elements lying adjacent each other while fig7 and 9 illustrate body elements which have posts which are rounded on their nose the body elements in the species shown in fig1 and 11 are more pointed so as to swing with respect to each other more on a knife edge rather than on a spherical surface body elements 66 and 68 are identical to each other and are similar to the body elements 52 and 54 there are two posts on each of the body elements with only the upper post being shown in fig1 and 11 post 70 engages in recess 72 as described above the recess has larger total included angle than the post to permit swinging of one body element with respect to the other until the edges touch the post 70 may be either conical or wedge shaped a pair of holes goes through each of the body elements in the manner seen in fig9 and a pair of flexible connectors extends through the holes flexible connector 73 is identified in fig1 and 11 fig1 illustrates adjacent body elements 74 and 76 these adjacent body elements are molded together rather than having posts and flexible elements to provide the spacing the flexibility and the attachment body elements 74 and 76 are two of a series of such body elements they are connected together by webs at the top and bottom the web 78 is shown in fig1 as connecting the two body elements the web 78.