Red nucleus (G55). CTB labelling in the red nucleus of a G55 fetus. Note the CTB labelling is bilateral, and forms a distinct tight cluster, with a greater density of cells towards the ventral region of the nucleus. Labelling is also observed in the nucleus of Darkschewitsch (Dk) and in the vicinity of the Edinger-Westphal nucleus (EW). 3 = oculomotor nucleus.