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1. Rh substances are found in amniotic fluid. Not all anti-Rh sera seem to be suitable for the detection of Rh substances in amniotic fluid. Careful selection of Rh antisera, as well as quantitative considerations, determine success or failure of their demonstration. 2. The baby's Rh type and not the mother's determines the occurrence of Rh substances in amniotic fluid. 3. There are Rh secretors and Rh non-secretors. At least four out of five individuals are secretors. 4. The secretion of Rh substance into the amniotic fluid would seem to be entirely independent of the secretion of the blood group specific substances. 5. The majority of Rh-positive amniotic fluids seem to contain both Rh1 and Rh2 substances. However, in certain instances fluids belonging to the pure Rh1 type or pure Rh2 type were found. 6. Three cases of erythroblastosis were described. All three came from Rh-negative mothers with Rh-positive babies. The amniotic fluids of all three failed to reveal the presence of Rh substances.

Abstract. A modification of Krijnen's cryopreservation method, using low intracellular concentrations of 17.5% glycerol and extracellular 4% sorbitol as additives, has been developed for liquid nitrogen freezing of small volumes of erythrocytes for a test cell panel. A technique for their subsequent successful storage in sterile, dextrose‐electrolyte maintenance solution (CP‐2) at 4°C after recovery is presented. By these procedures, the mean recovery of red cells after lytic losses from freezing and thawing injury was 94.1%. The manipulations involved in transferring, mixing and resuspending the red cells removed an additional 11.1–16.2%, resulting in an overall recovery of 80.5% for serologic tests. Less than 3% of the cells exhibited cumulative lysis at seven days maintenance in CP‐2 solution at 4°C, and the blood group antigens examined remained as potent as those in sterile, fresh ACD blood.