List of sources:
Edgar, J.I. Farm animals in Health and Sickness. Agricultural Journal of the Union of South Africa, 1911, Vol. 1, pp. 382-402.
FamilySearch: John Ingram Edgar. https://www.familysearch.org/ark:/61903/3:1:3Q9M-C9BP-CQCL-V?view=index&personArk=/ark:/61903/1:1:8W7H-T9ZM&action=view
Posthumus, P.J. Past veterinarians in South Africa (10th edition), Vol. 2, c.1992.