84 Lectures on Bacteria. [^ ix. 



for closer examination the Micrococcus of urea, the nitrifying 

 Bacteria, the mother of vinegar, the Bacteria of lactic acid- 

 fermentation, of butyric acid-fermentation, and of the viscous 

 fermentation of carbohydrates and other bodies, and, lastly, the 

 Bacteria of the decompositions of proteids. 



r. The normal urine of men and carnivorous animals if kept 

 exposed to the air acquires an alkaline and ammoniacal smell 

 in place of the acid reaction present in it when fresh. The 

 cause of this is, that the urea takes in water and is converted 

 into ammonium carbonate. The originally clear fluid becomes 

 clouded by the presence, as examination shows, of a number of 

 lower organisms, among which there may be a variety of Fungi 

 and Bacteria. Pasteur first proved that one of these Bacteria, 

 Micrococcus Ureae, Cohn, was the exciting cause of this process 

 of fermentation in urea (38; 25, p. 697), by showing that the 

 Micrococcus, if grown pure and cultivated in a pure nutrient 

 solution containing urea, causes the same decomposition in it 

 as in urine. 



The Micrococcus (Fig. 9) consists of small round cells about 

 0-8 ft in diameter, which usually, though not in- 

 variably, remain connected together in rows often 

 of more than 12 cells. These rows are in many 

 cases curved and bent in an undulating manner, 

 and are often ultimately wound into coils or small 

 Zoogloeae as they may be termed, in which the cells 

 appear to be irregularly heaped together. At the first beginning 

 of a culture the cells, according to von Jacksch, are cylindrical, 

 though not very much longer than they are broad ; they retain 

 this shape for some time, firmly united together in genetic 

 connection, forming therefore rod-like rows of short cylindrical 

 cells, and afterwards become rounded off. We may therefore, if we 

 please, speak of a ' rod-form,' but we shall not gain in clearness 

 by so doing. No distinct spores have been observed in this 



Fig. 9. Micrococcus Ureae, Cohn, from decomposing urine. Cells 

 separate or united in rows ( = Streptococcus). Magn. iioo times. 



