Estimation of glycogen in small amounts of tissue.

Studies on the glycogen content of biologic material have been handicapped by the fact that the more reliable chemical methods for analysis necessitate the use of considerable amounts of tissue. As a consequence, experiments which involve the use of small animals, such as tadpoles, or the isolation of a small specific tissue, such as a branch of a nerve or even repeated determinations of the glycogen content of an organ under observation can be carried out only by using procedures designed for macro estimations. The micro estimation of glycogen has been confmed, in the main, to histologic staining procedures which in my experience and in that of many others have been found to yield contradictory and erroneous results. The so called specific histologic reaction of glycogen has been employed by Mayer (8), Vastarini-Cresi (20, 21), Policard and Noel (15), and Roques (16). They have made use of such substances as cresolfuchsin, benzidene, iodine, resorcinol, fuchsin, rosaniline, and ammonium carminate. Much physiologic evidence has been submitted, based on the glycogen content of tissues analyzed by histochemical procedures, and in many instances it has been at variance with the results obtained by chemical analysis (17). Since the early work of Brucke (ll), Ktilz (7), Pfluger (9, lo), and Pfluger and Nerking (14), refinements in the technique of their analytic procedures for the estimation of glycogen have been made by numerous investigators, but at the present time the most satisfactory procedure, it seems to me, is the method of Pfliiger (12, 13). The refinements proposed for the Pfhiger method include the precipitation of the albumin by mercury