Analysis of the material written in the two manuscript volumes known as the "Old" and "New" Knox Catalogues has revealed that most of their contents are in the hand of Frederick Knox, younger brother of Dr Robert Knox. Frederick was employed by Dr Knox as his research assistant, and prepared detailed lists of the items in his brother's museum collection. He also dissected and prepared human and non-human specimens, many of which were described by Dr Knox in his numerous publications. As relatively little is known about Frederick Knox, this seemed a timely opportunity to evaluate his contribution to Knox's anatomy class in the extra-mural school. When in due course Dr Knox's success as a teacher of anatomy gradually declined, he decided to leave Edinburgh to pursue his career in London. It was at about this time that his brother Frederick also decided to leave Edinburgh to establish a new career for himself in the Antipodes. The present whereabouts of the majority of Knox's enormous teaching collection of anatomical preparations and his comparative anatomy collection are unknown, and suggestions are made as to their possible whereabouts.