130 



52 



the influence of temperature, we generally find the most pronounced flake formation 

 in broth near the maximum temperature. 



According to their biological qualities, the streptococci fall into two main groups. 

 The one forms, from all carbohydrates, pure dextro-lactic acid, with only a trace of by- 

 products, whereas the other forms lævo-lactic acid, besides appreciable quantities of other 

 fermentation products. The former group is by far the larger, and comprises not only the 

 principal streptococci of milk, but also the pathogenic forms known under the collective 

 term of Streptococcus pyogenes. They split up the sugars simply according to the formula 

 Q^i2^6 = ^Cgf/g^si arid the quantities of by-products, carbonic acid and acetic acid 

 (acetic acid and propionic acid generally in the proportion of 20: 1), which are formed, are 

 so insignificant that they do not practically speaking diminish the theoretical yield of 

 lactic acid. To the other group of streptococci belong the bacterium of sour cabbage. 

 Streptococcus brassicæ, and the slime former so Well known in sugar manufacture. Strep- 

 tococcus mesenteroides, which forms slime from cane sugar and mannite from lævulose, 

 and which can develop a considerable quantity of gas. With regard to nitrogenous 

 nourishment also, there is a difference between the two groups, the former preferring 

 casein peptone and the other yeast extract. The first group, again, generally prefers low 

 sugar concentrations, the second high (5% — 10% sugar). 



These two groups difi'er altogether so widely in biological respects that they must be 

 regarded as two distinct genera. And I therefore designated them originally as Dextrococ- 

 cus and Lævococcus, but relinquished these names afterwards, on finding that some few 

 bacteria belonging to the genus Lævococcus formed inactive lactic acid. For the first group, 

 it Would be tempting to employ the name Lactococcus, suggested by Beijerinck, if it 

 were not for the fact that so many pathogenic bacteria were allied thereto. I have there- 

 fore preferred simply to reserve the generic name Streptococcus for the first group. The 

 unavoidable alteration of names is thus reduced to the least possible; the only thing is, 

 that we are obliged for the future to give the term a somewhat more restricted meaning, 

 and only understand thereby such streptococci as form dextro-lactic acid. The second 

 group, being chiefly met with on souring vegetable matter and particularly on beets, I 

 have accordingly given the generic name of Betacoccus (Beta = beet). 



Genus: Streptococcus. (Abbr. Sc.). 



This genus I have divided into the following well-characterised species: Streptococcus 

 lactis, Sc. cremoris, Sc. maslitidis, Sc. thermophilus, Sc. bovis, Sc. inulinaceus, Sc. fæcium, 

 Sc. cjlycerinaceus and 5c. liquefaciens. In addition, there are also several strains — including 

 pathogenic — which are allied to these, and cannot exactly be placed under the mentioned 

 sj^ecies, but we have not encountered them often enough to ascertain their entire range of 

 variation, and I have not therefore ventured to establish them as separate species in 

 themselves. 



Streptococcus lactis (Table XIV). By this we understand the diplococcus which 

 predominates in sour milk, and which is knoWn in literature under the names of Bacterium 

 lactis (Lister 1878), Streptococcus acidi lactici (Grotenfeld 1879), Bacterium lactis acidi 

 (Leichmann 1894) Bacterium Güntheri (Lehmann & Neumann) and Streptococcus lacticus 



