The formation of ice in protoplasm

Though the effect of freezing plant tissues has been studied by various workers (Bachmetjew, 1901 ; Cameron, 1930 ; Gortner, 1929 ; Maximow, 1929 ; Payne, 1926 ; Pfeffer, 1903 ; Stiles, 1930) almost nothing is known of the way in which ice forms within living protoplasm. Molisch (1897) seems to have been the first to describe the appearance of minute blocks of ice within the substance of amœbæ frozen under the microscope in a specially constructed cold chamber. On thawing, the substance of the amœba had a sponge-like appearance, the spaces representing the places which had been occupied by the ice. When living muscle is thoroughly frozen ice forms between as well as within the fibres, and the relative quantity in the two situations depends upon the rate of cooling, as was first clearly shown by Plank, Ehrenbaum and Reuter (1916).