“…Maybe the cause '•' of this is the difference in viscosity of the concentrated and dilute enzyme solutions, because the concentrated solutions were absorbed into the discs slowly compared to the dilute solutions. It might have been better to pipette 0.07 ml/disc rather than dip the disc (Stark et aj.., 1953) • Over a certain range, the amount of enzyme per disc, the concentration of the starch and the concentration of the amylase, respectively, are linearly related to the diameter of the zone of hydrolysis (Stark et al, 1953).…”