The Ammoniacal Silver Solutions Used in Neuropathology

The methods of staining with silver salts, developed so largely by Fajersztajn and Bielschowsky in Germany, and by Ramón y Cajal and Del Rio-Hortega in Spain, are receiving increasing attention. Several procedures have been described for preparing the ammoniacal silver solutions which are used in these methods, and selective staining results have been attributed to each. The conflicting claims have led at times to actual controversy, and the present investigation aims to clarify this subject.1 (1) The method of Fajersztajn,2described in 1901, is of both historical and theoretical interest (as will be shown later). To a weak solution (exact concentration not given) of silver nitrate (AgNo3), Fajersztajn added ammonia until the brown precipitate which formed at first had completely redissolved. He then added more silver nitrate until a precipitate began to form again; the solution, supposedly "freed of excess ammonia" in this way, was filtered through