SUGAR IN" THE NUTRIENT MEDIUM. 131 



phtlialein as indicator. The difference in the titra- 

 tions gives the increase of alkali. 



The following will serve as an illustration of the 

 production of alkali by bacteria which in the pres- 

 ence of sugar form acid actively (5-7 c.c. normal acid 

 to 100 c.c.). One hundred cubic centimetres of a 

 nutrient medium containing traces of meat sugar and 

 rendered neutral by phenolphthalein used up : 



WHEN INOCULATED WITH BACTERIUM COLI. 



At the end of five days 0.1 normal sodium. 



At the end of ten days 0.1 normal sodium. 



At the end of fifteen days 0.25 normal acid. 



A special form of alkali production by bacteria is 

 the conversion of urea into ammonium carbonate: 

 CO(NH,), + 2H,0 = CO,(NH ( ), 



Leube (Yirch. Arch., 100, p. 540) first isolated a 

 few organisms from decomposing urine which pro- 

 duced ammonia from urea : micrococcus urese Leube, 

 bacillus ure?e Leube. This is also done by sarcina pul- 

 monum and a few other unnamed varieties. Fliigge 

 has described a micrococcus ureae liquefaciens. 



We have cultivated a large number of white lique- 

 fying and non-liquefying cocci and rods from decom- 

 posing urine. None of them possessed in any strik- 

 ing degree the power of setting free ammonia from 

 diluted urine or a nutrient medium treated with urea, 

 although they flourished in these solutions. It can- 

 not be denied that natural urea fermentation depends 

 partly on symbiosis. 



The ability to decompose urea does not seem to be 

 very widespread. Among twenty-four organisms ex- 

 amined Warington found that two alone (micrococcus 



