GROWTH AND DEVELOPMENT STUDIES IN CHILDREN In addition to the routine pediatric examinations, certain special anthropometric measurements on the children were recorded. Such data included age, weight, stature, sitting height, head circum- ference, biucromial width, bi-iliac width, and calf circumference. Roentgenographs of the Icft wrists were studied for skeletal maturation. LABORATORY PROCEDURES Hematological Examinations Complete routine blood counts were carried out with repeat counts on any persons showing abnormalitics, White blood counts and red blood counts were Obtained with the clectronic Coulter, which has proved to be a very satisfactory instrument for examinations of this type in the ficld. Differential counts were performed in the usual manner after stuining with Wright's Muid. Platelet counts were done by phase microscopy. Hemoglobin was determined by the cyan-hemoglobin technique with the Lumitron colorimeter, Hematocrits were ob- taincd by the microhematocrit: method, Serum proteins were determined with the Hitachi refractometer. Blood and serum samples for certain studies to be described below were collected and kept under refrigeration and finally shipped back for study. Blood smears were obtained for differential study, alkaline phosphatase examinations®, and basophil counts on 4000 white cells, as part of the leukemia survey. Bone marrow aspirations were done on 9 exposed people, and smears were prepared for differential counts and morphological studies. In addition, chromosome preparations were made on the aspirated material, Blood vole determinations were carried out on S$ unexposed Rongelap people and 7 Americans during the 1962 survey. During the 1961 survey such studies had been made on § Marshallese and 5 Americans. The analyses were done by the radioactive sodium chromate (Cr*!) technique.” *We ure grateful to Miss Lila Fliegelman of the Boston City Hospital for currying out the alkaline phosphatase analysis of blood smears. Blood samples were returned to the U.S. for electrophoretic studies for glucose - 6 - phosphuatc dchydrogenase and hemoglobin types.* Electro- phorctic studies or 171 sera for immuneglobulins were kindly carried out by Dr. R. Buller and Dr. A. Hassig at the Swiss Red Cross Laboratory, Berne, Switzerland. Protein-bound iodine determinations were made on sera from 10 individuals who had previousl' shownslightly clevated levels. The method of Foss, Hankes, and Van Slyke" was uscd.** For chromosome studies, short-term blood cultures were done on 10-m! samples from about 50 people, This blood was taken at the time of sampling for routine hematological studies. A modifi- cation «-f the technique of Moorehead! was used. The leukocytes were separated by centrifugation and placed in culture bottles with growth medium (Difco-199) and phytohemagglutinin (red kidney bean extract prepared by Dr. L. Schiffer of BNL). Dextran (3% ) was used in the initial separation in some cases but was discontinuce later since it was found to be unnecessary in view of the rapid settling of the red cells in the Marshallese, The cells were cultured for 3 days at 37°C, after which chromosome preparations were made as follows: Cells were separated by centrifugation, washed with Hanks’ solution, treated with hypotonic solution (distilled water plus Hanks’ solution) for 8 to 10 min, and fixed in methyl] alcohol—glacial acctic acid (3 to 1); smears were prepared by blowing a drop of the cell-rich sediment on a slide and air drying. Only occasional slides were stained with Giemsa's stain for evaluation in the field. Final stuining and chromosome studics were curried out at the Holy Ghost Hospital in Boston .+ Fasting blood sugar levels'* were obtained on 8 individuals who had shown positive urine sugars.t t Blood collected routinely for hematologi°We are prateful to tr. Samuel PE Hoyer of the Johns Hopkins Hospital for carrying out these studies. “*We are grateful to Dr. D. D. Van Slyke and Miss Dorothy Ripperger of BNL. for performing these analyses. + Under the direction of one of us (W. C. M.). We are grateful to Miss Geraldine Dowd and Miss Catherine Dunn at the Holy Ghost Hospital, Boston, for their assistance with these analyses. +t We wish to thank Dr. D. D. Van Slyke, Dr. L. VY. Hankes, and Miss D. Ripperger at BNL for carrying out these analyses.