Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class "lipids"
                 Class phospholipids
                   1.0 [Class glycerophospholipids] see Class phosphoglycerides [RC(=O)OCH2CH(OC(=O)R)CH2OP(=O)(OR)2]
                   2 Class phosphosphingolipids
                   2.1 sphingomyelin