Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               [cyclic compounds]
                 [heterocyclic compounds]
                   Class pyrazines
                   Class pyrroles
                   saccharin
                   Class thiazoles
                   oxolane [C4H8O; ~O[CH2]4~]
                   [tetrahydrofuran [C4H8O; ~O[CH2]4~]] see oxolane [C4H8O; ~O[CH2]4~]
                   2 Class heteroarynes