Mean value of this snake group. Snakes from Chantaburi and Chonburi representing the eastern population. Dried venom. The liquid (fresh) venom was weighed immediately before frozen at -20°C and lyophilized by Freeze Dryer (Modulyo, EDWARDS). Swiss albino mice (18-20 g) were obtained from laboratory animal unit of QSMI. The lethal toxicity of the venom was determined by intravenous injection of 0.2 ml of serially 1.4 fold-diluted venom solutions into the tail vein of mice. The LD50 was calculated by the method of Reed-Muench (1938) and 95% confidence limits by the method of Pizzi (1950).