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The excellent introduction to these volumes, presented in full in several translations, was written by Giovanni Di Guglielmo. Panels on human DNA, vitamin B 12 , blood and blood-forming cell cultures, hematologic genetics, leukemia, hemophilia and other hemorrhagic states, anticoagulants, and pediatric hematology are presented. To illustrate the wide scope of the volumes, one may cite the papers presented by William Dameshek on the Di Guglielmo syndrome, bone marrow infusion in hypoplastic anemia, and clinical experience with chemotherapy of leukemia; the discussion of the plasma clearance of intravenous doses of radioactive vitamin B 12 by D. L. Mollin and C. C. Booth; and the symposium on nucleic acids in which E. Chargaff discussed aspects of nucleic acid fractionation. Each paper is published in the language of the author. When this is not English, an English summary is supplied. For physicians interested in hematology, this set is highly recommended.

While a recent injection of ${}^{223}{\rm Ra}$ was retained as $t^{-0.50}$ , a long-term burden of226 Ra in the same man decreased as $t^{-1.7}$ . This dramatic difference in the rate of change of retention is predicted by the modified power function model with an observed rate of excretory plasma clearance of 126 liters/day. From the ${}^{223}{\rm Ra}$ data, the model predicts that the226 Ra burden should have reached transient equilibrium within the body ( $t_{{\rm y}}=6.7$ years) so that its retention today can be described by a final exponential. With a somewhat lower average rate of plasma clearance (72 liters/day, $t_{{\rm y}}=20$ years) the model would be consistent with the retention functions of Norris et al., Miller and Finkel, and the halftime for retention reported by Keane and Evans. Accordingly, it would be most interesting to measure the rates of plasma clearance in the...

Data on the disposition of insulin I 131 are reviewed and analyzed to determine the mechanisms responsible for insulin dispersion phenomena. The liver is indicated as the primary organ responsible for controlling plasma clearance rates by the following two methods: chemical reaction that degrades intact insulin supplied by the plasma, and the presence of a region that controls the rate at which insulin I 131 is made available to the reaction sites. The degradation reaction is apparently second order with respect to intact insulin I 131, so that combination of two insulin I 131 molecules with insulin glutathione transhydrogenase appears to be required for degradation to occur. A proposed model describing the insulin and glucose dispersion systems and the interaction between them is capable of explaining qualitatively how plasma insulin and glucose levels are maintained.

Several studies have been made in recent years on bone marrow lymphoid cells.5 The work of Osmond and Everett (1) and of Schooley and Giger (2) indicated that relatively few lymphoid cells from blood enter the normal marrow parenchyma of mice and guinea pigs. Previous work from this laboratory on the normal dog indicated that small lymphoid cells in bone marrow consist of two populations, one hematogenous, the other endogenous (3). Definite evidence for transformation of the hematogenous lymphoid cells into hemopoietic precursors was not obtained during the first 48 hours after injection of H3-thymidine. The present work extends these observations to the sublethally irradiated dog, in which the proliferation of lymphoid cells might be altered and their transformation into hemopoietic precursors stimulated. These problems were approached, as in previous work on the normal dog (3), by serial autoradiography with clamping of the hind limbs during the plasma clearance time of H3-thymidine injected into an anterior vein.

Despite Smith's 1 demonstration that under proper conditions the plasma clearance of diodrast closely approximates renal plasma flow, the detection of renal ischemia in human beings is evidently not a simple matter. Its existence in patients with hypertensive disorders has been claimed by some authors 2 and denied by others. 3 This report on a small series of subjects with normal and with diseased kidneys attempts to reconcile these divergent statements. Since no ratios for diodrast extraction based on human material have been published, the validity of the clearance method of measuring renal blood flow clinically is not conclusively established. Indirect evidence, however, suggests that the agreement between actual blood flow and estimated blood flow is even closer in human beings than in dogs. 4 There being no reason to doubt that the plasma clearance of inulin is an accurate measure of the rate of glomerular filtration, 5 the ratio