KEFIR. 



157 



2<t 



****> 



<^ 



threads, individual joints of which are readily demonstrated by the use of fuchsin. He states that he 

 observed threads from 10 to 40^ long. Most of these were not straight but wavy and bent. They 

 form commonly an interwoven, felt-like layer. The growth of Leptothrix threads due to unfavorable 

 conditions usually precedes spore formation. In such threads there is a row of spores, while in the 

 single vegetative cells which do not grow out into threads, there are always only two spores in a cell, 

 one at each end (fig. 39). The spore formation begins with the appearance at each end of the cell 

 of a small, bright dot, which gradually increases in size, becomes bounded by a sharp contour and 

 is finally converted into a true spore. These spores are always round and their diameter never 

 exceeds the thickness of the cell. The figure borrowed by von Freudenreich represents not spores 

 but germinating spores. The shortest cell observed with two polar spores measured 3^. Most of 

 them were 6 M long. The longest seen was 20^1. He was never able to find any cross-wall separating 

 the two spores, not even when he used Hartnack Imm. X. He, therefore, concludes that the two 

 spores are certainly inclosed in one cell. He could not make out in the vegetative cells whether the 

 spore formation was brought about by free cell-formation or by cell-division. On the contrary, in 

 the Leptothrix threads he found a plain cell-division. The round free-lying spores reach a diameter 

 of 1 ii. The germinating spores swell up to a diameter of 1 .6^. He was able to observe the germination 

 and has figured it, but it is not perfectly clear from his statements whether these germinating spores 

 were those from the Leptothrix threads, or those from the motile organism or from other non-motile 

 short rods or whether they really had anything to do with the organism concerned in the kefir sym- 

 biosis. After considerable discussion of the views of earlier writers on the systematic position of 

 the bacteria, he describes his organism, Dispora caucasica as follows : 



"Vegetative cells in the form of short cylindric rods, 3.2^ to 8mXo.8 m . In zoogloeae condition 

 the cells form white compact elastic clumps of considerable size (up to 5 cm.). The motile vegetative 

 cells have at one end a thin thread-like, wavy nagellum. The spores are round. Lying in the cells 

 they do not exceed the breadth of the 

 latter. When they are free they are 

 1 n in diameter. The round spores are 

 always arranged two in a cell, one at 

 each end." 



The kefir clumps do not appear to 

 lose power of growth by drying. They 

 shrink considerably, become dirty 

 brown and stone hard, but are able 

 again to resume their activity when 

 thrown into milk, and are preserved 

 by the mountaineers in a dry condition 

 for a long time. The author himself 

 preserved them in an air dry place for 



two months, and after a few days, when thrown into milk these could not be distinguished from 

 fresh clumps nor was there any perceptible difference in their power of fermentation. Under the 

 microscope the dry clumps showed a considerable number of changes. Many of the yeast-cells 

 were dead and those which remained alive were principally spherical. These dried ones contained 

 no spores. The Dispora when in spore condition is said not to be destroyed by boiling for an hour. 



The foregoing is the substance of Kern's paper in the Bulletin de la Societe Imperiale des Natural- 

 istes, Moscow, 1SS1. He sums up his conclusions as follows: 



(1) The little clumps, the ferment of the Kephir, afford an interesting example of a symbiotic 

 life commensualism (?) of yeast-cells and bacteria. 



(2) The yeast-cells are to be considered as the ordinary beer-yeast, Saccharomyces ccrevisiae 

 Meyen. 



(3) The bacteria, in the vegetative condition scarcely to be distinguished from Bacillus subtilis 

 Cohn, may, on the ground of very peculiar spore formation, be set off into a new genus, near the 

 genus Bacillus Dispora caucasica, nov. gen., nov. sp. 



(4) A distinct cell-membrane can be distinguished on the vegetative cells of the Dispora. 



(5) The motile cells of the Dispora have a thin, thread-like, wavy flagellum at one end. 



(6) Moreover, the little clumps, but especially the vegetative cells and the spores of the Dispora, 

 are very resistant to unfavorable influences. 



This paper is followed by two tables of figures. From them I have borrowed the two 

 figures 38 and 39. 



*Fig. 39. Spore formation in Dispora caucasica, and also mature and germinating spores (25). After Kern. In 

 his fig. 2$ at p, p, are masses of protoplasm which he states he observed to break up into two spores. In his figure 

 24 are a group of vegetative cells provided with a spore at each end and destitute of any cross-wall between them. In 

 his fig. 23, one, two and three are said to be stages following each other in spore development. 





Fig. 39.' 



