“…Electron microscopically the substance has a characteristic filamentous structure (Blackstad et al 1960, Bertelsen et al 1964, Ashton et al 1965. Histochemically the results hitherto presented are, however, rather conflicting (Busacca 1928, Dvorak-Theobald 1954, Gifford 1957, Arnesen et al 1963, Bertelsen ~t al. 1964).…”