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While the majority of investigators agree upon the carbohydrate fermentation by C. sporogenes, much undesirable confusion exists in the literature regarding the fermentation ability of C. histolyticum. The original paper of Weinberg and Seguin (1916) gives only a limited number of the biochemical properties of the new species with no data on sugar fermentation, except the statement that no gas is formed in agar-shake cultures containing sugars. Henry (1917), investigating one of the original strains isolated by Weinberg, reported this strain able to ferment glucose, laevulose and maltose from among the sugars tested. Results similar to those of Henry were reported by McIntosh and Fildes (1917) for other strains: fermentation was weak, but after 7 days' incubation was distinct with glucose, maltose and starch. Later, the same investigators (1919) reported the fermentation of glucose, laevulose and maltose. It should be noted that if these observations are correct this behaviour towards carbohydrates is the same as that shown by C. sporogenes. Hall (1922), and Reddish and Rettger (1924), found that C. histolyticum fermented the same sugars as did C. sporogenes. A year later, however, Hall (1923) reported that C. histolyticum failed to ferment sugars. Since a reasonable explanation for these anomalies was not evident, the possibility of an unknown contaminant in the culture of the earlier experiments was suggested. Kendall, Day and Walker (1922), Kahn (1924) and also Torrey (1925) deny the sugar fermenting ability of C. histolyticum. Thus, it is seen that highly contradictory results have been reported by the investigators studying this microorganism. That this contradiction still persists is evident from the fact that Bergey in the 1934 edition of his "Manual of Determinative Bacteriology" still arranges C. histolyticum under the sugarfermenting anaerobes, whereas Spray (1936) in his "Tentative Key to the Sporulating Anaerobes" lists the same bacteria among the nonsaccharolytic representatives. Since sugar fermentation is usually considered as one of the important criteria for the identification and classification of the

STUDIES were made of the conditions under which suspensions of Cl. sporogenes activate certain substrates as H-acceptors. Gaseous H2 was used as the Hdonator and the reactions carried out in Warburg manometers, in contrast to the methods used by other workers [Stickland, 1934; Woods, 1936]. It is believed that some of the objections to previous methods are eliminated by the method used in these studies. The method became possible only after it was found that Cl. sporogenes, under the proper conditions, actively utilizes gaseous H2. EXPERmIENTAL The strain of Cl. sporogenes used in these experiments was obtained from thef American Type Culture Collection and was labelled No. 319. The organisms were cultured at pH 7-3 in 3 % neopeptone solution, to which 1 % glucose was added. Anaerobic conditions were provided in McIntosh and Fildes jars. Following incubation for 16 hr. at 370 the culture was centrifuged. The precipitated organisms were then washed with a volume equal to the original culture of 0-85 % NaCl which had been previously boiled and cooled. After recentrifuging the organisms were resuspended in a previously boiled and cooled phosphate buffer solution of pH 7-2. Usually the organisms obtained from 250 ml. culture were suspended in 6 ml. phosphate buffer. One ml. suspension of Cl. sporogenes in phosphate buffer was placed in each Warburg manometer vessel, the side arm of which contained 0 5 ml. 0I1M solution of the prospective H-acceptor. H2, purified by passing through a