SINCE the original report by Sabbatani1 that the freezing-point depression of various dog tissues is on the average 150 per cent greater than that of blood, there has been continued interest in the possibility that intracellular fluid is hypertonic to extracellular fluid. Collip2, Leovey and Kerpel-Fronius3, Gomori and Molnar4, and Pichotka et al. 5 all confirmed Sabbatani's findings, as did Opie6 using melting-point depression.