THE FERMENTATION OF CELLULOSE 231 



its spores are round and 1.5 ^ in diameter, produced 

 at the end of the cells as in the allied species. Neither 

 kind stain blue with iodine and are therefore different in 

 this respect from Bs. auiylobacter. They have not yet 

 been cultivated on solid media and to separate them 

 is a tedious operation. 



Ex. 110. Prepare the following solution: 



Water . , . ... 1000 c.c. 

 Mono-potassium phosphate (KH 2 PO 4 ) i gr. 

 Ammonium phosphate . . . T gr. 

 Magnesium sulphate . . v .5 gr. 

 Sodium chloride, ' ,. . a small crystal. 



Pour into a 250 c.c. flask, and add 5 grams of calcium car- 

 bonate. Introduce about 3 grams of filter paper or blotting 

 paper cut into small pieces. Then add a small piece of fresh 

 horse dung or some mud from the bottom of an old pond. Fill 

 the flask completely with the solution, and insert a cork through 

 which passes a bent glass tube, arranged so as to collect any 

 gas given off. Keep in a warm room. Observe the evolution 

 of bubbles of gas which begins in three or four weeks in an 

 inverted test-tube over mercury. 



(1) When the test-tube is nearly full force into it with a syringe 

 or pipette, some concentrated caustic potash solution. CO 2 is 

 absorbed by the latter. Notice the diminution in the volume of 

 the gas. 



(2) Place the. thumb over end of the tube, turn the tube 

 mouth upwards and apply a light ; CH 4 burns. 



(3) Remove a bit of the filter paper after two or three months, 

 and tear off small pieces with needles ; mount on a glass slide or 

 cover slip, and examine for bacteria. Stain with carbol fuchsin 

 and methylene blue. 



