MICROBES, OR BACTERIA. 95 
form of yellow patches. It is also found in the albu- 
men of boiled eggs, in potatoes, ete. (Fig. 52). 
os 
© wane J 
& a 
Fig. 52.—Sarcina ventriculi, in different degrees of development 
(strongly magnified). 
III. THe MicroBe oF VINEGAR, AND ACETIC 
FERMENTATION. 
Pasteur has shown that the acid fermentation of 
alcoholic liquids is due to the existence of a special: 
microbe, acting like a ferment, which is developed on 
the surface of fermented liquors whenever they are 
abandoned to the contact of the air, in the presence of 
albuminoid substances. This microbe, which consti- 
tutes the mother of vinegar, and which is termed 
Mycoderma. aceti, is probably identical with Bacterium 
lineola, so often present in infusions, in stagnant 
pools, and even in spring water. It is a true 
bacterium (Fig. 48). 
The membrane which may be observed on the 
surface of liquids in course of acetic fermentation is 
formed of very minute elongated cells, from 15 to 3 
micro-millimetres in length, united in the form of 
