FERMENTATION 281 



there you observe a greater disturbance than ordinary 

 among the globules; keep your eye upon the place of 

 tumult, and you will probably see emerging from it a 

 long eel-like organism, tossing the globules aside and 

 wriggling more or less rapidly across the field of the 

 microscope. Familiar with one sample of this organism, 

 which from its motions receives the name of vibrio, you 

 soon detect numbers of them. It is these organisms, and 

 other analogous, though apparently motionless, ones, which 

 by decomposing the milk render it sour and putrid. They 

 are the lactic and putrid ferments, as the yeast -plant is 

 the alcoholic ferment of sugar. Keep them and their 

 germs out of your milk and it will continue sweet. But 

 milk may become patrid without becoming sour. Exam- 

 ine such putrid milk microscopically, and you find it 

 swarming with shorter organisms, sometimes associated 

 with the vibrios, sometimes alone, and often manifesting 

 a wonderful alacrity of motion. Keep these organisms 

 and their germs out of your milk and it will never pu- 

 trefy. Expose a mutton-chop to the air and keep it moist; 

 in summer weather it soon stinks. Place a drop of the 

 juice of the fetid chop under a powerful microscope; it is 

 seen swarming with organisms resembling those in the pu- 

 trid milk. These organisms, which receive the common 

 name of bacteria,^ are the agents of all putrefaction. Keep 

 them and their germs from your meat and it will remain 

 forever sweet. Thus we begin to see that within the 

 world of life to which we ourselves belong, there is an- 

 other living world requiring the microscope for its dis- 



* Doubtless organisms exhibiting grave specific differences are grouped to 

 gether under this common name. 



