I9IS] C. H. Cr ahm and H. S. Reed 41 



Cultures showing active production of ammonia from asparagin 

 and reddening of the agar were kept for 8 to 10 days. Some of 

 them, at the expiration- of this time, showed a yellowing of the 

 medinm aboiit the centre of the cidture. This is notably true of 

 B. putiduui and B. pyocyancus. The indications are that subse- 

 quent to the production of ammonia an acid is produced, due, no 

 doubt, to bacterial action on the cleavage products of the asparagin. 



Cytase. The presence and action of celkdose-dissoh'ing en- 

 zyme has been for a long time demonstrable microscopicahy. Re- 

 cently, however, Kellerman and McBeth- have described a conven- 

 ient Petri-dish rnethod for demonstrating the celhilose-dissoh'ing 

 action of bacteria and fnngi. 



The medium used in our exeriments was prepared according to 

 Kellerman's method, as follows : Exactly 400 c.c. of ammonium 

 hydroxide ( sp. g. 0.90) were dikited to 600 c.c. and an excess of 

 copper carbonate added. After standing all night, the excess of 

 copper carbonate settled to the bottom and the supernatant Solution 

 was siphoned off. Seven and one half gm. of dry filter paper were 

 added and the product shaken up at intervals. In a few minutes 

 Solution of the cellulose was complete. The Solution was diluted 

 to 5 liters and a i : 5 Solution of hydrochloric acid added, a few c.c. 

 at a time, until the cellulose settled to the bottom. Water was 

 added to make 10 liters, the cellulose allowed to settle and the su- 

 pernatant liquid decanted. The cellulose was then washed with 

 repeated changes of water containing a little hydrochloric acid, until 

 the blue color of the Solution disappeared. It was then washed 

 with distilled water until a silver-nitrate test showed the washins^s 

 to be free from chlorid. 



The cellulose was suspended in 500 c.c. of water containing 

 magnesium sulphate, 0.25 gm.; potassium Ijiphosphate, 0.5 gm.; 

 potassium chlorid, 0.25 gm.; ferrous sulfate, trace; sodium nitrate, 

 i.o gm.; agar agar, lo.o gm. The mixture was autoclaved and 

 poured into plates. 



2 Kellerman and AlcBeth : The fermentation of cellulose. Ccntralbl. f. Bükt., 

 Abt. 2, 34: 485 (1912). Kellerman: The excretion of c}^tase hy Pcnicillhim 

 t>iiiophiluiii, Circ. 118. Biir. PI. Ind., U. S. Dcpt. Agr., 1913. McBeth and Scales : 

 The destruction of cellulose by bacteria and filamentous fungi, Bull. 226, Biir. 

 PI. Ind., U. S. Dcpt. Agr., 1913. 



