How is Tita like a book of matches? (p.115-116)

Dr. Brown shows Tita how phosphorous combined with oxygen can create a flame. He shares with her one of his grandmother’s old sayings that everyone has a box of matches inside them that can only be lit by oxygen and a candle. The oxygen, says Dr. Brown is a lover and the candle can be any other pleasure in life. He claims that finding the elements to ignite the matches within is a task that each person must complete in order to nourish his soul. If a person does not discover what ignites their matches then the matchbox dampens and the soul leaves the body in search of something to nourish it.