Complex sentence: His first collection of poems was published in 1873, but he went in for medicine and practised as a doctor in London hospitals until 1882 when he was able to devote his full time to poetry.
Split into simpler sentences: His first collection of poems was published in 1873, but he went in for medicine and practised as a doctor in London hospitals until 1882. He was then able to devote his full time to poetry.