The drugs were injected in a small volume using earthworm Ringer solution for dilution ( Lockwood, 1961). The measurements of blood pressure used to evaluate vasomotor phenomena were made with Statham pressure transducers and an Offner dynograph. Haemoglobin content was measured according to the acid haematin method ( Hawk, Oser & Summerson, 1947) and by the direct analysis of iron content after Wong (1928). Oxygen tensions were analysed on a Beckman Spinco 160 polarographic oxygen analyser. Points on the dissociation curve were obtained after equilibrating the blood for at least 20 min.

The blood-gas analyses were carried out according to the methods of Roughton & Scholander (1943) and of Scholander & van Dam (1956). Oxyhaemoglobin dissociation curves were obtained from some animals which yielded an abundant supply of blood. At the end of an experiment the animal was exsanguinated and the blood analysed for haemoglobin content and oxygen capacity.

The animals were returned to moist soil or studied on a moist surface in contact with open air for periods of up to 6 days. The catheters allowed intravascular pressures to be monitored continuously as well as providing access for anaerobic blood sampling and injection of drugs. The methods used in inducing anaesthesia and implanting catheters have been described earlier ( Johansen & Martin, 1965). The experimental procedure included chronic cannulation of blood vessels with indwelling polyethylene catheters. An essential feature of the experiments was to draw blood samples and study intravascular pressures in non-anaesthetized animals under conditions as close to normal as possible.

Download giant earthworm