Until recently investigators have considered that results of blood sugar determinations obtained by fermentation and those obtained by copper reduction have been in quantitative agreement, and both of these methods have been regarded as being reliable. However, Aldo C. Castellani (1926) indicated that there may be fallacies in the various fermentation methods. His results showed that ordinary baker's yeast would ferment galactose, maltose, saccharose, lactose and many other carbon compounds other than glucose. Also, he found that Monilia Balanica, a bacterium, is the only organism found which fermented glucose, and did not ferment any of the other carbohydrates. Since this organism is never found in pure culture in aker's yeast, the ordinary fermentation methods of blood sugar determination are not dependable.