Born in Stockholm 15 April 1860, he was educated at Christiania (Oslo) University in Norway, which was then still united with Sweden, and at the Caroline Institute in Stockholm, where he graduated in 1895. He was appointed to the staff of the State Hospital at Christiania, and in 1909 was elected professor of surgery in the Royal Frederick University. Nicolaysen was elected an Honorary Fellow at the time of the last International Medical Congress in London in 1913. He died during the German occupation of Norway in the summer of 1944, aged 84. His principal work included studies of ileus, stenosis of the ureter, reflex dyspepsia from chronic constipation, ante-thoracic plastic operation on the oesophagus, gastrectomy for stomach ulcer, surgical treatment of chronic gastritis, and goitre in Norway. Publication: *Den strikturerende tyndtarmtuberkulose og dens kirurgiske behandling. *[Tuberculous stricture of the small intestine and its surgical treatment.] Christiania, 1908.