42 Bioclicniical Activity of Microorganisiiis [March, 



It is not always easy to obtain organisms which produce cytase 

 abundantly. Kellerman has described, in the papers cited, some 

 species of ^erobic bacteria and fungi which he foiind to be active. 

 Mixed cultures of these organisms may be obtained by selective 

 ciiltivation on the fohowing medium : fiher paper, in strips 2.0 gm. ; 

 ammonium chloride, o.i gm.; potassium biphosphate, 0.05 gm.; 

 calcium carbonate, 2.0 gm. ; water, 100. o c.c. 



This medium is placed in large Erlenmeyer flasks to form a 

 layer about one centimeter in depth. The flasks are inoculated with 

 fresh horse-manure, slimy mud from a pond, or with sewage from 

 a septic tank in active Operation. After a month's incubation trans- 

 fers are made to new flasks containing the same medium. In this 

 way the cellulose-destroying organisms are selected. The strips of 

 filter paper first become brown and then perforated with holes, and 

 a brown color is usually imparted to the Solution. Transfers may 

 then be made to cellulose-agar in tubes or Petri dishes. 



Solingen-"' has recently described a method for demonstrating 

 the cytolytic powers of bacterial colonies by the use of manganese 

 Compounds. A sheet of filter paper is dipped in a manganese sulfate 

 sol. and then in sol. of potassium permanganate. The resulting 

 manganic oxid is held in the paper and gives it a brown color. This 

 sheet is dried and sterilized in a Petri dish, then moistened with a 

 nutrient Solution and inoculated with cellulose-destroying bacteria. 

 The acids formed in course of the destruction of cellulose combine 

 with the manganic oxid to form light colored salts, which present 

 a conspicuous contrast on the dark background. 



Formation of lactic acid and other acids. It has been 

 known for some time that the addition of calcium carbonate to agar 

 gives a method for demonstrating the action of acids produced by 

 bacteria. Frequently failures have resulted from the difliculty of 

 adding just the proper amount of calcium carbonate. The method 

 which we have employed obviates this difliculty. 



Beef-peptone agar containing i percentof lactose is made and 

 put into test tubes as usual. Before plugging the tubes a small quan- 

 tity of calcium carbonate (0.5 to 2.0 gm.) is added to each tube. The 



3 Söhngen : Umwandlungen von Manganverbindungen unter dem EinHuss 

 mikrobiologischer Prozesse, Ccniralbl. f. Bakt., 2tc Abt., 40: 545 (1914)- 



