152 



74 



ance, and Nos. 46 (Pl. XXIV) and 47 are, from a purely morphological point of view, 

 more like micrococci than many of the true micrococci we have investigated. 



The above-mentioned morphological differences between the A- and A + X-forms on 

 the one hand, and the X- and 0-f orms on the other, render it likely that we have here to deal 

 with two distinct species. A's the former always (at any rate unless in a weakened state) fer- 

 ment arabinose, we will term them Betacoccus arabinosaceus, and as the latter (especially the 

 typical X-forms) can be isolated from most cowdung after enrichment in acid sugar broth, 

 we will call them Betacoccus bovis. As the betacocci are for the most part known under the 

 name oi Streptococcus mesenteroides,\i would have been reasonable to use the name Betacoc- 

 cus mesenteroides for one of the species, had it not been that both comprise strains which 

 do not form slime, and consequently also no mesentery. It is possible that the betacocci 

 should be divided into more than the two mentioned species. With all experiments in this 

 direction, however, I have felt that I was working on treacherous ground, as these bacteria 

 exhibit such great variability in almost all respects. 



Appendix to Streptococci, 



Not all chainforming cocci are true lactic acid bacteria, as e. g. the bacterium 

 described by Boekhout, which in his opinion contributes to the aroma formation in 

 the creamsouring^). Cultivated in milk it inverts a part of the lactose and forms a 

 trace of acetic acid and perhaps also a little non-volatile acid. It is killed at a tem- 

 perature of 57°. Its optimal temperature is 20°, and it already thrives badly at 31°. 



We succeeded in isolating the same bacterium from commercial starters. It forms 

 no appreciable quantity of acid in milk and does not attack the casein. It is a pro- 

 nounced milk bacterium and grows badly on artificial substrates. In stab culture on 

 whey agar with 1 "/o Witte peptone it shows distinct growth after one day at 20° but 

 ürst after 2 — 3 days at 30°. The chains in youthful state have thick capsules. 

 They can be very long but easily break in pieces. The bacterium is Gram positive and 

 does not develop oxygen with peroxide of hydrogen, which makes it likely, that — 

 in spite of its lack of acid formation • — it is related to the lactic acid bacteria. 



Perhaps it is a variety of Sc. cremoris, that has lost the power to form acid but 

 on the other hand has got the power to form aroma increased. 



') Vereeniging tot Exploitatic eener Proefzuivelboerderij te Hoorn. Verslag over det jaar 1917. Al- 

 ready some years before his death V. Slorcl} has found the same as Bockhoiil, but his work lias not 

 yet been i)ublislied. 



