"HEAVY WATER" AND TUMOR GROWTH

Pursuant to a suggestion by Prof. Harold C. Urey, the effect of "heavy water" on tumor growth has been investigated. This liquid consists of water in which ordinary hydrogen, of mass 1, has been replaced by its isotope, deuterium ("heavy hydrogen"), of mass 2.1When replacement is complete, the substance is no longer water but deuterium oxide, quite another material with specific gravity, vapor pressure, and freezing and boiling points differing from those of water. High concentrations, such as have been shown detrimental to lower forms of animal life and to seeds, could not be employed in the projected experiment, however, on account of their cost, and it was necessary to be content with a preparation in which somewhat less than 0.5 per cent (from 0.40 to 0.42 per cent, according to determinations made by one of us) of the hydrogen was deuterium. Still, as ordinary water has but