The blood of Lophius piscatorius is poor in haemoglobin, the volume of red cells being only 17%. The plasma contains less than 40 g. of protein/1., of which only 6 7 % is albumin. This explains its low osmotic pressure. As is well known, it contains more crystalloids than mammalian blood, A(depression of freezing-point) being 0–84°, the same figure being found at Naples, Woods Hole and Plymouth. This rather high concentration is not due to organic constituents, that of total non-protein nitrogen being of the same magnitude as in mammals; it is mainly due to a high content of sodium chloride. Chloride is at a concentration of 15.3 m.equiv./1oo ml., sodium at 18.5, while in mammals they reach 9 and 15 respectively.Total non-protein nitrogen concentrations in plasma are similar to concentrations in mammals; themain non-protein nitrogen constituents of plasma are neither urea, ammonia, uric acid or allantoin, but trimethylamine or trimethylamineoxide. Of our analysis 37% of non-protein nitrogen of plasma remain unidentified, so far as we can rely upon our chemical methods. The power of concentration of the kidney for non-protein nitrogen on the whole is not high; it varies up to fifteen times. But the degree of concentration by the kidney, small for most constituents, even for trimethylamine, seems to be very high for creatine which is the main representative of non-protein nitrogen. Of our urine analysis, 30% of non-protein nitrogen remain as yet unidentified.

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IN 1940, one of us and M. Dor investigated in the dog the relationship between renal blood flow, systemic pressure and oxygen consumption in kidneys transplanted in the neck. We found that between 60 and 150 mm. Hg. increase in the blood pressure raised the renal blood flow, but that from about 100 mm. up to 160 mm. there was no relationship between blood pressure and blood flow in the kidney. We concluded that "Pour les reins enerves, les valeurs critiques de pression et de debit veineux sont de l'ordre de 130 mm. et 3 c.c. respectivement. Au-dessus de ces chiffres, debit veineux et consommation d'oxygene varient beaucoup plus en fonction d'autres facteurs encore inconnus qu'en fonction du regime de la pression ou de la circulation".Later [Brull and Louis-Bar, 1950], using a mechanical heart with coagulable blood [Brull, 1950], we extended our investigation to include pressures up to the limit of resistance of the renal capsule. The urine flow followed regularly the variations in arterial pressure. The venous flow, although eventually influenced by variations of arterial pressure, did not follow so closely in 7 cases out of 16; it did not respond at all in 9 cases out of 16. We suggested that it was necessary to find out whether the blood carries to the kidney one or several factors which regulate vasomotor responses as well as secretion.In the meantime, Selkurt, Hall and Spencer [1945] investigated, by indirect measurement of the blood flow, the problem which we had studied in 1940. Although unaware of our results, they came to the: same conclusions. In 1951, Shipley and Study perfused kidneys at low, normal and high pressures, using a Dale-Schuster pump and heparinised blood. Unaware of our results of 1950, they too arrived at similar findings, but emphasised that at very high pressures the blood flow, hitherto independent of the pressure, was again influenced. Recently, Brull and Louis-Bar [1953] perfused innervated kidneys in situ, using a mechanical heart with coagulable blood, and showed that innervated kidneys were even more independent of the systemic pressure than denervated ones. Our results were similar to those of Shipley and Studv.151

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1. Kidneys originating from thyroxinised dogs, when transplanted simultaneously with control kidneys to a donor anæsthetised with chloralosane, have been found to secrete more rapidly and to give larger responses to saline infusion and to hypophysectomy than the controls. 2. The method adopted and the results obtained demonstrate that the diuretic effect of thyroxin is due, at least in part, to a direct action on the kidney.

SUMMARYKidneys of Lophius piscatorius L., perfused with heparinized blood, respond to a high tension of CO2 in the blood by a drop in urine flow and in their capacity for concentrating Mg. At the same time, but independently, CO2 reduces the blood flow. Both cyanide and fluoride may stop or reduce water secretion and Mg concentration, according to the concentration used, showing that both these activities are dependent on aerobic processes and presumably on the integrity of the carbohydrate cycle.

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