KEFIR. 161 
Bacillus caucasicus is described as follows: On ordinary gelatin plates it does not grow at all. 
Only once, as already stated, did von Freudenreich obtain it on a gelatin plate exposed to anaerobic 
conditions according to Miquel’s method. Other times, using the same method, he did not obtain it. 
Also on milk-sugar gelatin plates he never observed it. Having once obtained it, it grows in stab- 
cultures even in ordinary gelatin but then first after a long time. On milk-sugar gelatin plates he 
often had no growths; at other times microscopic colonies. On the surface of milk agar plates, on 
the contrary, he often obtained colonies. Upon this it produces small, flat, grayish colonies which 
appear circular to the naked eye. With a weak magnification they are seen to have irregular contours 
and are not uniformly circular; they also appear whitish and granular. This granulation is produced 
he states, by the irregular arrangement of the bacilli, plain to be seen on the edge, out of which the 
bacillary forms project. In ordinary nutrient bouillon he could not obtain any growth, not even at 
35° C. In milk-sugar bouillon there was a slow growth at 22° C.—nothing to be seen for the first 3 
days, but at 35° C. the growth is faster. The reaction was acid. It produces no coagulation in milk 
although the reaction becomes somewhat acid. ‘The taste of such milk was slightly acid and astringent 
similar to that produced by the smaller streptococcus when grown in milk. There was a moderate 
gas formation. There was no growth on potato. In milk-sugar bouillon it appears ordinarily as a 
straight bacillus with rounded end, often with a shining point at each end. This appearance corre- 
sponds well, he says, to the phenomenon interpreted as spores by Kern. ‘Their slight resistance to 
heat, however, shows that they are not spores; also when exposed to staining media the bacillus 
stains in toto which would not be the case if these bodies were spores. The organism stains easily 
with the common aniline dyes, and also by Gram’s method. The breadth of Bacillus caucasicus is 
about ry, the length 5 to 6y, but long forms are also found which are then crooked. It is very feebly 
motile. A good photomicrograph of this organism is shown in his fig. 5, table 1 (fig. 40). Its resistance 
to external influences is slight. It endured drying 1 day. It was 
regularly killed by a drying of two or more days. Nevertheless, 
it lives a long time in the kefir grains, which he thinks is explain- 
able by the fact that it is protected from the action of the air. 
It was killed, as already stated, by 5 minutes exposure to 55° C., 
while 2.5 per cent carbolic acid killed it in 30 seconds. Corrosive 
sublimate 1 : 1000 killed it in one experiment in 1, 2, and 60 
minutes, but not after 5 and 15 minutes. ‘This contradiction is 
attributed to dissimilar resistance of individual bacilli. ‘The acid 
was estimated in terms of lactic acid, but I find no statements 
concerning its determination. 
When inoculated separately into milk he could not obtain 
with cultures of these organisms anything corresponding to kefir. 
Moreover, with two organisms alone he could not obtain kefir. 
The yeast and the large streptococcus caused the milk to coagu- 
late with a small amount of gas formation but no further change. 
The small streptococcus combined with the yeast and inoculated 
into milk produced gas formation and a sour taste, but no kefir fermentation. The amount of gas 
formed was variable. ‘This he attributes to decrease in the virulence of the streptococcus. Finally, 
with the yeast and the Bacillus caucasicus he could not obtain kefir. Also when he inoculated all 
four of the micro-organisms together the experiment miscarried regularly at the beginning. The 
lactic acid ferment took place, the milk coagulated, but nothing further happened. 
Von Freudenreich states that throughout his studies he had many failures but that finally he 
frequently obtained good kefir by inoculating milk with mixed growths of the organisms obtained 
by rubbing kefir grains on slant agar. Usually the first flask of milk inoculated did not yield kefir, 
but when transfers were made from this to a second flask of milk good kefir was often obtained. He 
seems to have been more successful in using this source of inoculation than pure cultures of the 
separate organisms mixed, although on the second or third transfer from milk to milk he states that 
he also obtained kefir from these. He states that sometimes he obtained a drink which could scarcely 
be distinguished from kefir by use of the yeast and the two streptococci. 
He was never able to produce the kefir grains synthetically, and he considers that the réle of the 
Bacillus caucasicus is still involved in a good deal of uncertainty. Its presence seems absolutely 
necessary to the symbiosis, but just what its function is in the fermentation he does not know. 
Podwyssotsky (French edition of 1902) says nothing is known respecting the origin 
of kefir. There are various hypotheses current among the natives of the Caucasus respect- 
ing it: (1) The kefir grains are the direct gift of God through his Prophet Mohammed, 
*Fic. 40.—Bacillus caucasicus. From a photomicrograph by von Freudenreich. x 1000. 
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