Sentence:  By medicine life may be prolonged, yet death / Will seize the <WSD>doctor</WSD> too. 
Meaning of the word marked with <WSD> tags:  A physician; a member of the medical profession; one who is trained and licensed to heal the sick or injured. The final examination and qualification may award a doctor degree in which case the post-nominal letters are D.O., DPM, M.D., DMD, DDS, in the US or MBBS in the UK.