438 SOIL SCIENCE 



McBeth, Scales, and Smith (30), and Scales (71). The cellulose agar 

 prepared as described in the above mentioned publications has given very 

 satisfactory results not only with cellulose-dissolving bacteria, but also 

 with filamentous fungi. The medium also appears to be well adapted to 

 the study of cellulose destruction by species of Actinomyces. We have 

 frequently observed colonies of Actinomyces which dissolve the cellulose 

 very rapidly in the cellulose agar, forming a clear enzymic zone about the 

 colony which furnishes unmistakable evidence of the cellulose-dissolving 

 power of the organism. Krainsky (36) in his recent studies of the Acti- 

 nomyces, has reported the cellulose agar plate method as unsatisfactory 

 for determining the cellulose-dissolving power of these organisms. How- 

 ever, he was able to demonstrate the cellulose-dissolving power of several 

 species of Actinomyces by the use of paper pulp or strips of paper on 

 silica jelly, and also by means of cellulose hydrate prepared by the zinc 

 chloride method. The reason for the failure of Krainsky to secure satis- 

 factory results with the cellulose agar plate method is not clear. How- 

 ever, since these organisms grew luxuriantly upon the cellulose agar pre- 

 pared by us and dissolved the cellulose very rapidly, it would seem that 

 the tmsatis factory results reported by Krainsky may be due to certain in- 

 attention to details in the preparation of the cellulose precipi- 

 tate. In order to secure a uniformly fine amorphous precipitate, it 

 is necessary to carry out the operations with considerable care. 

 It is believed that much of the difficulty experienced in the prepa- 

 ration of precipitated cellulose is caused by precipitating in solu- 

 tions that are too concentrated. If either the copper-ammonium-cel- 

 lulose solution or the acid used in precipitating the cellulose is too 

 concentrated, a product is frequently secured which is not only dif- 

 ficult to wash, but is very unsatisfactory as a culture medium. A very 

 uniform and satisfactory amorphous precipitate can be secured by adher- 

 ing strictly to the following method which is a slight modification of tiie 

 method originally proposed. 



1. Pour 1 liter of ammonium hydroxide, sp. gr. 0.90, into a glass- 

 stoppered bottle ; add 250 c.c. of distilled water and 75 gm. of pure cop- 

 per carbonate; shake the solution vigorously until all the copper is dis- 

 solved. (From 10 to 15 minutes is ordinarily required.) 



2. To the copper-ammonium solution add 15 gm. of high grade, sheet 

 filter paper ; shake vigorously at intervals of 10 minutes for one-half hour. 

 Examine the solution carefully to see that the paper is completely dis- 

 solved. If any particles of paper remain in the solution, the shaking must 

 be continued until the solution is perfectly clear. 



Dilute 250 c.c. of the ammonium-copper-cellulose solution to 10 liters 

 with tap water ; add slowly with frequent shaking, a weak hydrocloric acid 

 solution prepared by adding 500 c.c. of concentrated acid to 10 liters of 



