His parents were James, a prominent physician and civic leader, and Elizabeth MacDonnell (née Clarke, died 1798).
On 1 January 1847, he performed the amputation with the assistance of four surgeons, including Carmichael, successfully anaesthetising the patient for the procedure.
Later that evening he reported the procedure as "Amputation of the arm, performed at the Richmond Hospital, without pain", submitted to the Dublin Medical Press for publication.
He recognised that his apparatus was crude and not fit for long operations, and proposed that experiments should be conducted on animals to further establish the ratio of air and ether to be used on patients.
He was appointed to a committee of the Surgical Society of Ireland created to further examine the application of ether in surgery, which reported on 20 January 1847.
In 1879 he published a history, The Ulster civil war of 1641, in which he sought to vindicate his ancestor Sir Alexander Macdonnell, 1st Baronet against charges of cruelty.