Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class glycoconjugates
                 Class glycopeptides [carbohydrate-peptide]
                   Class glycoproteins [carbohydrate-protein]
                     Class immunoglobulins - antibodies
                       Class immunoglobulin A
                         1 Class immunoglobulin A1
                         2 Class immunoglobulin A2