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The effects of physostigmine 1 mg i.v. were studied on the analgesia, sedation and reduction in respiratory rate induced by morphine 10 mg/60 kg i.v. in 10 patients recovering from surgery. Within 5-10 min, physostigmine abolished the somnolent effect of morphine and restored the respiratory rate to pre-drug values. Analgesia, assessed by an independent observer and by the patient was, if anything, increased by physostigmine. The analeptic effect of physostigmine lasted 40-60 min.

Isotopes of water (deuterium oxide and tritium oxide) have been used for the determination of total body water in certain mammalian species (Hevesy & Hofer, 1934;Pace, Kline, Schackman & Harfenist, 1947; Soberman, Brodie, Levy, Axelrod, Hollander & Steele, 1949;Haigh & Schnieden, 1956;Langham, Eversole, Hayes & Trujillo, 1956; Fallot, Aeberhardt & Masson, 1957). However, the techniques involved in these determinations have limited use, being either difficult, expensive or timeconsuming. Recent advances in scintillation counting techniques (Haigh, 1957) have made it much easier to estimate one of these isotopes of hydrogen, namely tritium. The purpose of the present paper is to describe how far such scintillation counter techniques can be applied to the determination of tritium in urine and plasma and the estimation of degree of error involved. The use of such techniques for a comparative study of total body water in a number of mammalian species and of water turnover under tropical conditions in one species, namely man, is also presented. METHODS 0-5 ml. of tritiated water or processed tritiated plasma or urine (see below) was added to 8 ml. of absolute ethanol and 10 ml. of scintillation solution (3 g 2:5-diphenyloxazole/l. sulphur-free toluene). The mixture was shaken and then centrifuged at approximately 1500 rev/min for 2-3 min. 5 ml. of the supernatant fluid was placed in the special counting container supplied with the N612 Ekco Scintillation Counter. This scintillation unit was kept at -20°C in a deep-freeze cabinet and its amplifier set at maximum gain. It was connected to a N 530E Ekco Automatic Scaler unit which was set at H.V. 1200 and Discrimator bias of -5 V. The scaler received a stabilized current from a constant-voltage stabilizer (Servomex AC 2 Mark IIB). Unless otherwise stated, all specimens were counted for 1000 sec and were allowed to cool in their counting containers for 1000 sec at -20°C before counting.Preparation of urine. 3*5 ml. of urine was mixed thoroughly in a test-tube with 0 5 g of activated charcoal. The resultant sludge was filtered through a Whatman No. 2 filter paper and 0 5 ml. of the filtrate was then added to 18 ml. of the alcohol-scintillator mixture, shaken and centrifuged, and a 5 ml. portion taken for counting. J. M. FOY AND H. SCHNIEDENPreparation of rat, cat, guinea-pig or rabbit plasma. 0*5 ml. of plasma was added to 18 ml. of the alcohol-scintillator solution mixture. After thorough shaking the mixture was centrifuged. 5 ml. of the clear supernatant fluid was then withdrawn and placed in the counting container before counting.Preparation of human plasma. Since it was found that the above method of preparation for rat plasma gave a coloured (orange-yellow) supernatant liquid with human and baboon plasma, another method was also investigated. The plasma was precipitated with 10 % trichloroacetic acid (Langham et al. 1956) and 0 5 ml. of the clear colourless filtrate was mixed with 18 ml. of alcohol-scintillation fluid mixture. 5 ml. of this final mixture was used f...

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Summary1. An investigation has been made of the effects of cadmium and zinc ions upon the contractile response of the guinea-pig isolated ileum to methacholine, histamine, potassium ion and a.c. field stimulation. The metal ions depress the response to all of these agents. 2. Radioisotope studies showed that cadmium and zinc ions have very much larger apparent volumes of distribution than sorbitol, both within whole ileum and within strips of the longitudinal smooth muscle layer. The results of these studies were indicative of surface binding and/or intracellular accumulation of these ions. 3. It is suggested that cadmium and zinc ions directly depress smooth muscle contractility in a non-specific manner. This action may result from their binding to or accumulation within the muscle cells.