"Our brains are seventy-year clocks. The Angel of Life winds them up once for all, then closes the case, and gives the key into the hand of the Angel of the Resurrection"

This quote by Oliver Wendell Holmes is a metaphor for life and death. He is recommending that our lives are predetermined which we are all provided a set quantity of time to live. He compares our lives to a clock, with the Angel of Life winding it up as soon as and after that handing the key to the Angel of the Resurrection. This suggests that our lives are predetermined which we have no control over when our time is up. It likewise suggests that death is inevitable which we need to maximize our lives while we can. The quote is a suggestion to live life to the max and to value the time we have. It is a reminder that life is valuable and that we must make the most of it while we can.