Nematic 8CB and MBBA slabs, with a homeotropic zone between two parallel -1/2 disclinations (and associated splay bend zones), are subject to an electric or magnetic field acting transversely to the disclinations. Optical microscopic study of the static and dynamic characteristics of the boundary zones is carried out for the first time. The growth rate of the zones is linear in field-strength. AS the field is progressively elevated, the zones widen nonlinearly, and merge to form a splay-bend wall in the mid-region. At a high enough field, the homeotropic region is squeezed out of the wall and a pair of wedge disclinations forms in its place. One of these combines with a -1/2 line originally present in the field off state, forming a loop that progressively collapses.