The somata of proprioceptive fibres in extra-ocular muscles have been localised to the trigeminal meseneephalic nucleus in twelve cats. This has been achieved by the demonstration of unequivocal changes of chromatolysis in the neurons of this nucleus following selective orbital resection of extra-ocular muscles. The localization of the somata has been shown to be bilateral, and a topographical subdivision in the nucleus in which different muscle groups are represented in different areas of the nucleus has also been demonstrated.