104 DAIBY BACTERIOLOGY 



directly, and a few of them were found to contain some Gram- 

 negative rods in addition to the usual Gram-positive rods. The 

 Gram-negative rods must be classed with Bacterium cloacae or 

 rather with the Proteus species ; they are peritrich and non- 

 spbring ; they ferment practically all sugars x with copious 

 evolution of gas, production of alcohol and small amounts of 

 acid (acetic and lactic). They coagulate milk, forming a slimy 

 film which sticks fast to the bottom of the flask, and on shaking 



FIG. 63. Section through a Kefir Grain, x 1,000. 



clots together, enclosing other microorganisms and casein. These 

 rods therefore doubtless play some part in the formation of the 



1 In addition to the common mono and disaccharides, they ferment 

 raffinose and inulin, and, among the alcohols, glycerol and mannitol ; but, 

 like the true lactic acid bacteria, they do not ferment dulcitol. The 

 aerogenes bacteria mentioned by Kunze in his exhaustive work on Kefir fer- 

 mentation ("Centralblattf. Bakteriologie," 2 Abt., 1909, Bd. XXIV., p. 112) 

 are possibly identical with these. This investigator also describes certain 

 butyric acid bacteria which are said to play an important part in Kefir 

 fermentation, and, as a matter of fact, a butyric acid fermentation can 

 always be induced by inoculating stale Kefir grains into sterilised milk. 

 The butyric acid fermentation, however, only does harm, and it can only 

 be regarded as a defect here as in all other milk products. In order to 

 avoid this 'fermentation, the Kefir grains should be revived by inoculation 

 into milk distributed in shallow layers. Kefir grains occasionally have 

 certain Mycodermse on the surface. The author was formerly inclined to 

 regard these as organisms which normally contributed towards the growth 

 of the grains, but now regards their presence as a defect. 



