Movements of potassium have been observed in isolated right and left auricles of rabbits by means of radioactive tracer. The tissues have been immersed in a modified Krebs saline at 370, and in these conditions showed only small changes in ionic content over periods up to 6 hr.The extracellular volume, determined with inulin and with 2"Na, was large (44.1 ml./100 g. tissue), and accounted for about 3.8% of the tissue potassium. Left auricles exchanged without gross inhomogeneity: the rate of exchange was about 1.5% of the total tissue potassium/min., though it was probably higher in the first half-hour or hour after preparation. In right auricles the exchange was less homogeneous and included a faster component than that observed in left auricles. Digoxin and ouabain reduced the influx and had no appreciable effect on the efflux of potassium, so that the auricles lost potassium. The threshold concentrations which produced effects within 20 min. were of the order of 10-6 for ouabain and somewhat higher for digoxin. Irregularities or failure of contraction occurred when the tissue potassium was reduced by about 15%. Loss of potassium was accompanied by gain of sodium, but the tissue appeared unsuitable for making estimations of the rate of sodium movement.

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The roles of genetic and non-genetic factors in the haematology, growth and clinical features of sickle cell disease have been studied in nine identical twin pairs (six homozygous sickle cell disease, three sickle cell-haemoglobin C disease). A comparison group of 350 age-gender matched sibling pairs, selected to have an age difference of <5 years, was used for assessing the concordance of numerical data. Attained height, weight at attained height, fetal haemoglobin, total haemoglobin, mean cell volume, mean cell haemoglobin and total bilirubin levels showed significantly greater correlation in identical twins than in siblings. Twins showed similarities in the prevalence and degree of splenomegaly, susceptibility to priapism, and in onset of menarche, but other clinical complications were discordant in prevalence and severity. These findings suggest that physical growth and many haematological characteristics are subject to genetic influences, but that non-genetic factors contribute to the variance in disease manifestations.

Little information is available about the actions of 2: 3-dimercaptopropanol (BAL) in poisoning by lead salts, and so far as is known nothing has been published about its effect on the distribution of lead in the body. -This paper provides some new observations on the distribution of lead, indicated by the use of Pb2l2 (thorium B) as a tracer, and on changes in the distribution after the administration of BAL. METHODSRadioactive lead was obtained from the deposit on a charged button exposed to a thorium source. A button with Pb212 (intensity of about 1 millicurie) was heated gently in a slightly acidified 0.01 per cent (wlv) solution of lead acetate', so that the Pb2l2 deposit was exchanged for part of the lead in the solution. For administration to rabbits a solution was prepared such that the volume injected (2.0 ml.) contained 2.07 mg. of lead (as acetate) per -kg. body weight (i.e. 0.01 mM./kg.) incorporating 100-300 microcuries of Pb212 dissolved in 4 per cent (w/v) dextrose. Young rabbits of both sexes and various breeds and of average weight 1.3 kg. were used. Injections were made into the marginal vein of one ear. After injection the rabbits were placed in metabolism cages and allowed access to water but not food. Their bladders were emptied by suprapubic pressure before injection and six, twelve, and eighteen hours afterwards, unless the rabbits were killed earlier. The animals were killed by a blow on the head one, six, or twenty-four hours after the injection of lead acetate. Solutions of BAL were freshly prepared in 66 per cent (v/v) aqueous propylene glycol and were injected into the paravertebral muscles as discussed below.Immediately after death the thorax was opened, and blood was collected by bleeding from the great veins. Clotting was prevented with heparin, and the samples were centrifuged immediately. The organs were then dissected, starting with those in which a low content of lead was expected, and taking care to avoid contamination between different tissues. Complete organs were washed with water, dried of superficial moisture between filter papers, and weighed; they were then chopped finely and, in organs weighing less than 10 g., ashed entire. From other tissues samples weighing 2 to 10 g. were ashed. Liver samples were taken from well-mixed choppings of the entire organ. Muscle samples were taken from the outer part of the thigh. Bone epiphysis and diaphysis were obtained from the long bones of one hind limb and one fore limb. Marrow was completely removed from the central cavities of these bones and estimated separately. The samples of diaphysis were therefore practically marrow-free; the values for epiphysis, ribs, vertebrae, and skull vault were influenced by the amount of marrow contained in the cancellous tissue. The injected ear and the small piece of cottonwool used to control bleeding were taken as an independent sample, and in the majority of experiments the uninjected ear was taken as a control. The amount of lead lost by leakage at the site ofinjection could therefore be asse...

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