Ester wax as a medium for embedding tissue for the histological demonstration of glycogen.

IT is generally recognized that glycogen is a very labile substance which disappears rapidly from tissues unless treated by special methods of fixation and embedding. The recognized and widely used techniques, advocated by the standard microtomical treatises, call for fixation in a glycogenprecipitating fixative (absolute alcohol; picro-formol-alcohol; picro-dioxane) followed by celloidin embedding. Since glycogen is considered to be readily soluble in water, if paraffin sections are to be used, special precautions are advocated: sections must be . flattened on slides with 70 per cent, alcohol instead of albumen-water; mounted sections, after removal of wax, must be brought into absolute alcohol and then into 1 per cent, celloidin in absolute ether. This latter process covers the section with a thin film of celloidin which 'seems to prevent the diffusion of the glycogen from the section into the water' (Carleton, 1938). Most workers further emphasize that water must be avoided during the subsequent staining processes. On the other hand, Bensley (1939) in a recent account of staining methods for glycogen makes no mention of the necessity for the celloidin film, but merely states that 'tissues may be embedded in paraffin or celloidin'; and when staining 'sections may be brought down to water'. In recent work on cestode physiology we have had available a considerable quantity of material rich in glycogen, namely, the plerocercoid larvae of the cestode Ligula intestinalis which contain seldom less than 30 per cent, glycogen (dry weight; Markov, 1939). It has thus been possible to test the embedding'methods on this material on an extensive scale. Confirmatory experiments were carried out with rabbit liver.