Born in Christianstad in 1857, and matriculated in 1875 at the University of Upsala. After he had completed his preliminary studies he went for clinical work to the Carolinska Institut and Serafimer Lasarett in Stockholm. In 1888 he was appointed Docent in Surgery and Obstetrics at the University of Upsala, and in 1891 was named Professor in these subjects and became Chief Surgeon at the Upsala Hospital. Here he reorganized the scientific side of the hospital work, at that time in need of much improvement. Lennander was an assiduous worker and a voluminous writer. He is best known for his work on the sensory nerves of the peritoneum. In recognition of his researches he was made a member of the Swedish Academy of Sciences, a much coveted distinction. He was one of the Hon Fellows elected on the occasion of the Centenary of the Royal College of Surgeons, while the University of Edinburgh conferred upon him its Doctorship of Laws, and he was made an honorary member of numerous societies. From youth up he had suffered from cardiac troubles, which increased as the years went on, so that the performance of his duties often involved much difficulty. He spent long periods in sanatoria, and latterly had to perform operations sitting in a chair. He died at the comparatively early age of 51, on March 15th, 1908. There is a portrait of him in the Hon Fellows'Album, and the same portrait is the frontispiece to his "Collected Works", published by the University of Upsala in three volumes in 1912. These volumes contain some seventy of his contributions to transactions, etc, illustrated by plates, and many are written in English. The papers forming the contents of the three volumes are his bibliography. The University presented the book to the Royal College of Surgeons' Library. Lennander is best known for his writings on peritoneal innervation and acute peritonitis, but he wrote also on tracheotomy in croup, the relations between croup and diphtheria, operations for myoma and diseases of the bile passages, the treatment of perforated duodenal and gastric ulcers, surgical measures in nephritis, and on local anaesthesia. He was a contributor to German, English, and American text-books and works of reference.