A recenit study in this laboratory demonstrated the effect of controlled fermentationi of maple sap on the quality of the sirup obtained (Naghski et al., 1957). These fermentations were carried out in 50-L glass carboys. When the glass containers were replaced by galvlanized, 10-gal canis, variable results were observed. It was noted that, in new cans, several of the inocula diminiished almost to sterility within a few days, whereas in older cans, growth progressed at about the usual r.ate. This germicid-al effect of the cans was tentatively attributed to the ziniC coatings. The oligodynamic effect of metals, including zilc, on microorganisms received considerable attenition sevreral decades ago. Inhibition by zinc has been reported for many types of bacteria (Hotchkiss, 1923;