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WHEN patients with pre-existing liver disease are subjected to abdominal operations there is a danger of precipitating hepatic failure. This problem has been discussed by Ravdin and Vars (1950) who thought it was probably due to anoxia from interference with the blood-flow to the liver at the time of operation. It was also considered by Shackman, Graber, and Melrose (1953) in the course of a study of the effect of general anaesthesia on liver bloodflow in patients without hepatic disease. They reported an average fall of 30 per cent in the estimated hepatic blood-flow (bromsulphthalein extraction method) following anasthesia. They thought that while this could be well tolerated by a patient with normal hepatic function, such a fall in liver bloodflow in a patient with a diseased liver might be sufficient to hasten the development of liver failure. Some experiments arising from an investigation of the mechanism of toxic hepatic necrosis in the rat (Stoner, 1956) will now be described since they show that the circulation through the necrotic liver is more sensitive than that through normal liver to external influences such as anaesthesia and laparotomy. METHODSThe experiments were performed on albino rats of the Porton strain (mean body-weight 315 163 g. ; standard deviation) fed on MRC diet 41 (Bruce and Parkes, 1949). Hepatic necrosis was produced by giving 0.2 ml. carbon tetrachloride (analar) per 100 g. body-weight by mouth as a 20 per cent solution in arachis oil 24 hours before the experiment. This dose constantly produced severe necrosis of the liver visible to the naked eye. Some of the controls were given an equivalent dose of arachis oil alone.The liver temperature was measured and its blood-flow assessed by the internal calorimetry method developed by Grayson (1952)~ as previously described (Stoner, 1956). In this method the liver blood-flow is assessed by measurements of the thermal conductivity of the liver, using a special thermocouple recorder, and expressed as the conductivity increment (Bk) due to the flow of blood through the tissue around the recorder. Grayson and his collaborators have shown that Bk is proportional to the blood-flow. The application of this method to pathological situations, the interpretation of the results, and the precautions required have been discussed elsewhere (Stoner, 1954(Stoner, , 1956). In these experiments the recorders were inserted in the liver under ether anzsthesia on the day before the administration of carbon tetrachloride.On the day of the experiment the rats were anaesthetized with sodium pentobarbital (veterinary nembutal-Abbott) 5 mg. per IOO g. body-weight intraperitoneally, and as soon as they had reached the stage of surgical anaesthesia the abdomen was opened by a median incision with a lateral extension to expose the right side of the liver as described by Seneviratne (1949). The temperature and bloodflow (6k) in the liver were recorded before giving carbon tetrachloride, before anasthesia, during anaesthesia, and at intervals for at least 30 minute...