List of sources:
Cape of Good Hope. Report of the trustees of the South African Museum,1903.
Cape of Good Hope Government Gazette, 9 January 1885, pp. 41-45: List of licensed medical practitioners in the Cape Colony.
FamilySearch: John Fergus. https://www.familysearch.org/tree/person/details/L2ND-375
General Directory of South Africa, 1908, 1909, 1916.
Medical and pharmacy register for the Colony of the Cape of Good Hope, 1893, 1907.
National Automated Archival Information Retrieval System (NAAIRS). http://www.national.archives.gov.za/naairs.htm Documents relating to Fergus, John / Fergus, Dr J.
South African Medical Directory for 1897. Cape Town: Cape Times, 1897.