Xviii.—polyethylene Glycols as Histological Embedding Media: With a Note on the Dimensional Change of Tissue During Embedding in Various Media

Synopsis The literature is reviewed. A technique for embedding tissues in polyethylene glycol 1,000 mono‐stearate (Nonex 63B) after preliminary infiltration with polyethylene glycol 900 is described. Preliminary dehydration in alcohol is not required and at no stage is the temperature of the tissue raised above 40° C. Measurement of tissue before and after embedding in Nonex, paraffin and celloidin shows that there is significantly less shrinkage in Nonex. It is shown that the celloidin in celloidin‐Nonex mixtures used experimentally for embedding penetrates tissue. The difficulty of mounting Nonex sections is discussed. Nonex sections stain well, phosphatase activity is well preserved and at least part of the lipid is preserved. It is concluded that the use of Nonex is specially indicated for tissues liable to shrinkage artefacts and may have some advantage for histo‐chemistry.