[The metallic cations' capture through the external mucopolysaccharide surface coat encompassing the neurons (author's transl)].

Union of several iron compounds and other metallic cations to the duodenum mucines and to the neuronal surface mucopolysaccharides is studied. The results differentiate clearly the behaviour of the duodenum mucosubstances and neuronal surface mucosubstances. The duodenum mucines only attract to certain cations, in such a way that their union seems to be specific. On the contrary the neuronal surface mucopolysaccharides attract to most of the assaied metallic cations. These results coincide with other biochemical ones that prove that cationic attraction by the acid mucopolysaccharides is of electrostatic nature. To reveal the metallic cation union to the mucopolysaccharides is used ammonium sulphide in solution. The physiological role of these perineuronal mucopolysaccharides in relation to nervous impulse transmission and propagation is discussed attending to the obtained results.