The agar cup-plate ' diffusion technique has been applied to the quantitative determination of enzyme activity, principally to amylase, polygalacturonase, cellulase. protease and pectin-esterase. With all enzymes so far examined, the relationship between diameter of zone and log(amount of enzyme) is linear over a wide range, and may be used for the quantitative estimation of the enzymes. The cup-plate assay of polygalacturonase, like viscometric methods, measures the initial destruction of the colloidal properties of pectic acid, and, owing t o the complex nature of polygalacturonase, bears no simple relationship t o the assay of polygalacturonase by the estimation of glycosidic hydrolysis. H. Experiments are described in which flour stored in jute bags, the fabric of which had been impregnated with insecticides, was exposed to infestation by the species Ephestia kuhniella, Ptinus tectus and Tribolium confusum. The use of 1 % (w/w) of DDT in the fabric provided good protection against the first two named, and fair, but by no means absolute, protection against T . confusum. Transfer of insecticide to the flour occurred to an extent sufficient to be classed as contamination.
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