234 ALCOHOL, VINEGAR, SAUER KRAUT, TOBACCO, SILAGE, FLAX 
The Vinegar Organism.—The mother of vinegar is a soft, 
semi-solid mass, commonly forming a scum on the surface of the 
fermenting alcohol. Vinegar is not formed if this material be 
lacking, and a very small bit placed on the surface of an alcoholic 
solution soon extends itself and covers the whole surface, in- 
ducing an active acetic acid formation. This mother of vinegar 
proves to be a mass of microérganisms. It was first named 
Mycoderma by Persoon, who studied it in 1812, without having 
any suspicion that the skin was the cause of the acetic acid. 
Later, Kiitzing, showed that this skin was made of numerous 
minute, living organisms, and positively asserted that they were 
the cause of the acetic fermentation. But the chemist Liebig 
checked the advance of discovery by his own theories of fermenta- 
tion, which regarded the whole class of phenomena as chemical 
processes. 
It was eventually Pasteur who demonstrated that the process 
is really a fermentation due to the activity of the microdrganisms 
in the mother of vinegar. An examination of this material shows 
it to be made of a mass of bacteria. Pasteur used for them the 
name Mycoderma aceit, but he did not study them sufficiently to 
show what they were, although he demonstrated their relations 
to vinegar-making. Hansen later proved they were bacteria, 
and showed that in the different samples of ‘‘mother”’ there are 
several varieties. Henneberg still later increased our knowledge 
of the bacteria, so that we now know that there are at least fifteen 
varieties of these vinegar organisms, differing from each other 
in various respects, such as their optimum temperatures, the 
amount of acid they will produce, etc. Bact. acett, Bact. pasteur- 
tanum, Bact. kitzingianum, Bact. xylinoides, Bact. orleanense, and 
Bact. xylinum are names applied to the most important types. 
All of these acetic bacteria have certain very characteristic 
points which they share in common, thus forming a group by 
themselves. They all exist in three different forms, shown in 
Fig. 47. They may form chains of short rods, looking like 
