Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class purine bases
                 adenine [1≈NCH=NC(~2)=C(N=CHNH~2)C(NH2)≈1]
                 guanine [1~NHC(NH2)=NC(~2)=C(N=CHNH~2)C(=O)~1]
                 purineᵀ [1≈NCH=NC(~2)=C(N=CHNH~2)CH≈1]