316 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



rvoL. 10 



on the enzymes. The greatest enzymatic activity for A. niger 

 was therefore observed during the first 3 days of incubation. 

 Aspergillus ochraceus, on the other hand, was considered to 

 produce no injurious acids, and its enzymes increased in activity 

 until the inhibiting autolytic substances began to be formed. 

 The exo- and endo-enzymes were similar in their action. Deam- 

 idizing enzymes were indicated by the detection of small amounts 

 of ammonia in the treated peptone and casein. 



In the work on the N metabolism of the Actinomyces Waksman 

 and Curtis (16) and Waksman ('18, '19, '20) made use of Nessler's 

 reagent for qualitative ammonia tests and the aeration method 

 for quantitative determinations; amino N was estimated by the 

 "micro" method of van Slyke, nitrites by the color imetric method 

 of Griescz, and active acidity with Clark and Lub's indicators. 

 The results may be summed thus. Nearly all Actinomy cetes were 

 capable of liquefying gelatine and many could haemolyze blood 

 agar and liquefy blood serum ; in other words many of these forms 

 have a strong proteoclastic power. This process was followed 

 in protein solutions by means of amino acid determinations. The 

 amount of splitting was directly proportional to the extent of 

 growth. Although on long incubation a considerable quantity 

 of NH, accumulated, the production of NH, from amino acids 

 and proteins by Actinomyces was not considered characteristic. 

 None could fix elementary N ,. With a suitable C source nearly 

 all species could reduce nitrates to nitrites. In the order of as- 

 similability as sources of N stood, speaking broadly, proteins 

 and amino acids, nitrates, nitrites, amides. With glycerine as a 

 carbon source NH 4 salts were the poorest sources of N; but with 

 dextrose both NH* salts and amides were well assimilated if 

 the medium did not become too acid. 



Waksman and Joffe ('19) reviewed some of the papers on the 

 application of hydrion determinations to bacteriological work; 

 they then gave the results of investigations on the effect of 

 Actinomycetes on the reaction of Czapek's solution containing 

 various C and N sources. The colorimetric method was used. 

 It was shown by growing the organisms on NaNOi and varying 

 the C source that the Actinomycetes, unlike many bacteria, are 

 not producers of acid from carbohydrates; in fact under the con- 



