IX—MICROSCOPIC OBSERVATION OF LIVING CELLS DURING FREEZING AND THAWING

SYNOPSIS A freezing slide has been constructed for obtaining very low temperatures on the microscope stage, and an optical system evolved for studying the process of freezing and thawing by direct visual observation, micro‐projection, or photomicrography. The behaviour of suspensions of fowl spermatozoa, rabbit red blood corpuscles, and amœbae, when frozen and thawed, has been studied. In presence of glycerol the processes of crystallization and dissolution are modified, spermatozoa resume full motility, and blood corpuscles are preserved from haemolysis. Intracellular crystallization has so far been observed only in amoebae, which fail to revive on thawing. The mode of action of glycerol in preserving some cells from death at low temperatures is discussed.