Fig. 8. Data tracings of venom pressure recorded from the venom duct of Naja nigricollis. Note that stimulation of the M. protractor pterygoideus (PP) had minimal influence on venom pressure, and there was no additive effect when stimulated simultaneously with the M. adductor mandibulae externus superficialis (AMES). Note the marked increase in venom pressures recorded at the venom duct compared to those recorded from the fang tip (Fig. 7).