How does Thomas Mann use imagery in Buddenbrooks?

Examples of Imagery:

"But this bitter feud with my own brother, with your eldest son, is like a hidden crack in the building we have erected. A family should be united, Father. It must keep together. 'A house divided against itself will fall.'"

"...often, the outward and visible material signs and symbols of happiness and success only show themselves when the process of decline has already set in. The outer manifestations take time—like the light of that star up there, which may in reality be already quenched, when it looks to be shining the brightest."