1. The effect of paraffin wax embedding on the lability of glycogen in sections has been tested using as material (a) plerocercoid larvae of Ligula intestinalis; (b) rabbit liver.
2. It was found that glycogen in tissues was very impermeable to wax, and where large masses of glycogen occur prolonged embedding is essential.
3. Improperly embedded material lost glycogen easily; it was concluded that this loss takes place during the processes of cutting and flattening sections.
4. The effect of prolonged embedding was to make tissue hard and refractive. This difficulty was overcome by embedding in Steedman's ester wax.
5. Ester wax blocks allowed thin sections of very hard material to be cut with ease.
6. Ester wax sections brought down to water did not lose glycogen even after standing in water for 7 days.
7. It is emphasized that glycogen exists in two forms: an insoluble desmo- form and a soluble lyo- form. It is suggested that the latter does not dissolve from sections in water because its highly branched molecule is held by the coagulated protein network.