ABSTRACT

I. Theoretical considerations.—The conditions which determine whether a homogeneous liquid will solidify into the crystalline or into the vitreous state are discussed and a brief account of the rôle of the speed of crystallization, V, and that of grain formation, N, is given. These concepts are applied to the causes of the death due to crystallization of nondehydrated organic cells, and the physical conditions of cooling are developed under which such organisms can be solidified with a minimum of crystallization, assuring to this extent the preservation of their potential life.

II. Technical considerations.—Methods for obtaining cooling rates up to 104 deg. sec.−1 applicable to organic cells in a highly dispersed state are developed. As subject for the experiments, pure strains of yeast (Saccharomyces cerevisiae) were chosen on account of the high sensitivity to low temperatures. As death criterion, the permeability of the cells to a standard aqueous solution of methylene blue was chosen, the death rate was thus determined microphotographically or with a counting chamber. Different techniques of exposure favoring and preventing crystallization are developed.