Natura - nature actualia - actual entities Mundus Plinius - physical world naturalia - natural bodies "crystal-kingdom" chemical substances chemical compounds Class imines [RN=CR2] 1 Class aldimines [RN=CHR] 2 Class ketimines [RN=CR'2 (R'≠H)] 3.1 Class Schiff bases [RN=CR'2 (R≠H)] 3.2 Class azomethines [RN=CR2 (R≠H)] 4 Class quinonimines