AbstractThe appearance of deoxypentosenucleic acid (DNA) in muscle expressible fluid has been taken to indicate rupture of the sarcolemmas, with liberation of nuclear material. When fish fillets are frozen more and more rapidly, the expressible nucleic acid suddenly rises to a maximum, which is thought to correspond with the point of formation of intracellular ice crystals. In ultra‐rapid freezing, there is also a rise in expressible DNA, probably owing to a different kind of cell damag