Colin Mackenzie and William Lowder were at the forefront of advances in obstetrics in the 18th century and taught midwifery in Southwark, London. Mackenzie was a student of William Smellie and was a consultant in the first cesarean operations in England. He also was involved in the disputed discovery of the circulatory relationship between the placenta and uterus. He brought his discovery to the attention of John Hunter, who in turn reported to his brother William Hunter, who then incorporated the discovery into his "Gravid Uterus" without acknowledging either Mackenzie or his brother John.
William Lowder perfected the vectis, a forceps with a single blade, devised to move and flex the foetal head. It could be folded and carried in the pocket and was the most popular device type until the 1890's. He was also a cosultant on the first English cesarean operations.
From the description of Lectures on the theory and practice of midwifery, [ca. 1775?]. (National Library of Medicine). WorldCat record id: 463627745