“…Some experimental tumours can be stored at -79°C or -196°C and retain their transplantability without the use of any cryoprotectant (Ising, 1960) although it is likely that, in some cases at least, this is due to preservation of tumour viruses rather than intact cells (Gye et al, 1949). The addition of glycerol (Hauschka et al, 1959) or DMSO (Greenberg, 1966) has generally yielded more consistent results, but precise information on optimum conditions and quantitative estimations of survival are available for very few malignant cells.…”