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VITAL MANIFESTATIONS OF BACTERIA. 23

of fermentation are a jelly-like substance, dextrane and carbonic
acid. The optimum of temperature lies between 25°-35° C. As
cane-sugar is easily inverted, it serves the purpose of fermentation
as well as grape-sugar.

d. Butijric Acid Fermentation.
Few trustworthy observations have been made in regard to
the butyric acid fermentation of carbohydrates. The experi-
ments of Fitz, and more recently those of Fliigge, have made it
appear probable that several species of bacteria are able to cause
a fermentation of carbohydrates, in which butyric acid results as

Fig. 6.

''8|,'/'?V

Bacillus bctyricus.
a, h. Tadpole- and Spindle-shapes, partly with spores ; e, Zoogloea condition.
A, Germination of a spore. (After Prazmowski.)

the principal product. These seem to be, for the most part, an-
aerobic, which makes it difficult to obtain them in pure culture.
Butyric acid, as well as lactic acid fermentation, was formerly
supposed to be due to the action of a single organism. This bac-
terium of butyric acid fermentation (Bacillus butyricus, Clostrid-
ium butyricum, Yibrion butyrique, etc.), whose morphology,
development, etc., have been thoroughly investigated by Praz-
mowski,^ appears in form of rods from 2-12/i long and about 1.0/i
broad, either single or in long chains, or in zoogloea (Fig. 6);
frequently the rods grow out into long threads. During spore-
formation the cells exhibit peculiar changes of form ; spindle,
ellipsoidal, or tadpole shapes appear, which in certain parts