The enamel plaque replaced one put up in 1977 and which had faded until it had become almost illegible.
Direct descendants, including great and great-great grandchildren of Sir Louis came from Hastings, Taihape, Martinborough, Waihi, Karori, Masterton, Christchurch, Blenheim and Banks Peninsula just for the unveiling, but were staying at Banks Peninsula over the weekend for an ''unofficial family reunion'', great-great granddaughter Julie Barnett, of Taihape, said.
They watched Sir Louis' grandson, Dick Barnett, from Diamond Harbour, along with Prof Andre van Rij, the Ralph Barnett Professor of Surgery and associate dean of research at the Dunedin School of Medicine, unveil the plaque.
Sir Louis funded the chair in memory of his son Ralph, who died in World War 1.
Dick Barnett recalled visiting Sir Louis in his house in Hampden as a small boy.
''We were always greeted with a smile,'' he said.
Their grandfather was given the task of looking after the boys outside on visits, telling them ''the most wonderful stories'' and paying 3d pocket money if they covered the bottom of a sand-bucket with weeds.
Mr Barnett said Sir Louis would place the money in their hands then tell them: ''Take it to the shop and watch it go, take it to the bank and watch it grow.''
Sir Louis (1865-1949) was best known for founding the Royal Australasian College of Surgeons in 1927, as a pioneer in the research of hydatids and use of gloves and masks in operating theatres in Dunedin under then new aseptic principles.
After studying at the Otago Medical School under a junior university scholarship for two years, he completed his third year at Edinburgh, graduating with first-class honours.
In 1891, after two years at Middlesex Hospital, in London, he returned to Dunedin as a surgeon and acting lecturer at the Otago Medical School.
Sir Louis came to live in the Hampden House, built in 1918, when he retired in 1925, but continued his interest in medicine and hydatids research until his death, aged 85.
