immunizing sera. The latter possessed the normal antitoxic and antihacterial properties. Cobra venom, in a 1% solution, maintained in liquid air for 9 days, presented an unaltered toxicity (Lumiere and Nicolas, Province mcdicale, Sept. 21, 1901). According to Pictet (1893), pfomains were affected by exposure to temperatures of-100°t o-200°. 4. Viruses. A strain of bacteriophage active on B. coli and one active on staphylococci, frozen at-78°(with solid CO2) and thawed 20 times consecutively, did not lose any of their activity (Sanderson, 1925). D'Herelle (''The Bacteriophage and Its Behavior," p. 300, Baltimore, 1926), however, reported that while the phage (one for staphylococci and one for dysentery bacilli) was not affected in young filtrates, it was inactivated by 1 to 3 freezings in liquid air, when treated in filtrates more than 17 days old. Rivers (1927), using 19to 90-day-old filtrates of a phage lytic for B. coli, observed that, after 12 freezings in liquid air, the phage was completely inactivated when physiological salt solution was used as a diluent, and that it was partially inactivated when the diluents were Locke's 18 solution, distilled water, or hrotli, the dcni-cc ol" iiiactivatiou decreasing in the order given, lie then cxixMiincuted with dilutions of 1-10 and 1-1000 of tlie slock filtrate and found lliat an increased dilution with salt and Locke's solution increased the percentage of phage inactivated while, on the coiiti'ai'N', increased dilution with distilled water or brotii did not. According to Stockman and Minett (li)2G), the virus of foot and mouth disease was not destroyed by repeated freezing in ammonia brine. Pictet and Yung (1884) reported that the cow-pox vaccine was inactivated after two consecutive exposures of respectively 108 hours to-70°a nd 20 hours to-130°. According to Barrat (1903), an exposure of the rabies virus to the temperature of liquid air for 1 to 5 hours did not inactivate it. Salvin-Moore and Barrat (1908) found that a stay of 30 minutes in liquid air did not affect the graftable mouth cancer. Gaylord (1908) obtained identical results with the same material maintained in liquid air for 80 minutes. Rivers (1927) observed that the herpes virus in a brain emulsion was not inactivated by 12 freezings in liquid air ])ut was inactivated when frozen 24 times in an emulsion diluted 1-20 or more with Locke's solution. Similar results were obtained by the same author with vaccine virus, which resisted 12 freezings in a testicular emulsion diluted 1-10, 1-100, and 1-1000, Imt the titer of the virus decreased after 24 freezings at. dilutions of 1-10,000 and 1-100,000 and the virulence was completely destroyed after 34 freezings at a dilution of 1-100,000. Rivers investigated also rims III and found it to be readily inactivated after 12 freezings at dilutions of 1-10 of his stock emulsion. The results on the infracellulars can be summarized as follows: 1. The enzymes, toxins, bacteriophage and viruses investigated are not affected by a freezing of their 28 })osiii-(' to (lilT...

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One of my chief objectives in this paper is to point to a unifying principle, namely, the predominant effect of cooling velocity, in the multiple transformations that take place in aqueous solutions at low temperatures (between 0" and -195O C.). The transformations examined here have been a subject of investigation in this laboratory for several years, and the material on which the paper is based is taken mostly from our work. The occurrence of phase transitions in aqueous solutions is considered here from the viewpoint of the biologist who seeks, in the freezing of simple physical systems, some basic information on the mechanisms of injury by freezing and of prevention of that injury.The expression phase transitions includes primarily the passage from the liquid, amorphous state into the crystalline state, but also miscellaneous other transitions, such as solidification in the amorphous state, transformations within the amorphous state (such as the so-called glass transition), various forms of incomplete crystallization (some of which have been designated in the literature as vitrification), various types of "recrystallization," and the passage from one crystalline system to another.Investigations on phase transitions in aqueous solutions presuppose a knowledge of the transitions undergone by pure water. I shall therefore examine, in a first part of this paper, the information that we have on water, taking it primarily from the literature. In the second part I shall present the data on solutions, mostly as supplied by our own observations. Each of these two parts will consist of two sections: one (A) treating typical crystallization, and the second (B) treating miscellaneous other transitions.Since practically all solutions encountered in biological processes are dilute, their solidification takes place in two steps: a first, called hereafter primary crystallization, in which the solvent (water) freezes out, while the solutes become more concentrated, and a second, designated as secondary crystallization, in which the components of the concentrated solution solidify (precipitation of the solutes, or of their hydrates, or simultaneous crystallization of the solute-solvent mixtures, in particular of the eutectic mixture). There will thus be two stages to examine under crystallization of solutions: (a) the primary, and (b) the secondary crystallization.The general division of the paper will then be as follows: (A) Typical crystallization \(B) Miscellaneous transitions (1) Water (a) Primary crystallization (b) Secondary crystallization (A) Typical crystallization (B) Miscellaneous transitions (2) Solutions 549

Apparatus, Material, and Working MethodsThe measurements were made with the high frequency bridge described by H. Fricke (1925a, 1925b), and Fricke and Morse (1925, 1926). The frequencies used vary from 0.5 to 1024 kilocycles.The conductivity cell is of the same kind as that described by Fricke (1926). The tissue is fastened in the hole of an isolating diaphragm of celluloid which divides into two parts a solution of KC1 in which the platinized platinum electrodes are immersed. The hole is cylindrical and measures 1/4 of an inch in diameter and 1/8 of an inch in length.The piece of tissue to be placed in the hole is cut with a cylindrical borer which has an inside diameter of 0.266 inch. After being fastened in the hole, both ends of the piece are shaved with a razor blade. In experiments in which the tissue is to be injured it is cut 1/2 inch in length and a borer with an inside diameter of 0.400 inch is used instead of the one referred to above. Then after being treated 283