Examples of CTB immunolabelling. High magnification micrograph of CTB labelled cells in a G140 fetus. A) Labelled cells lie within and around the nucleus ambiguus (Amb): CTB labelled cells are of large size and have an irregular triangular shape with pronounced dendritic labelling (arrow). B) CTB labelled cells in the raphe pallidus (RPa) nucleus which spanned the ventral midline: the majority of these labelled cells were medium in size and rounded in shape. C) Labelled neuron in the vestibular nucleus (Ve): CTB labelled cells had a variety of shapes and consisted of medium to large size cells.