Chapter 8 mentions that the human body is constantly changing. What analogy does it use to explain this idea?

In Chapter 8, the text uses the analogy of a lamp's flame to illustrate the ever-changing nature of the human body. It explains that like the flame, which appears to be the same from beginning to end but is actually different every single moment, the body is also in a constant state of flux. What is seen one moment perishes in the next. The chapter points out that while the stages of childhood, youth, and old age are visible, the transition between them happens so naturally that no one ever notices the exact moment of change, reinforcing this idea of continuous, imperceptible transformation.