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56 



of „Tätmjölk" Baclerium ladis longi, and the bacterium of the long "whey Streptococcus 

 hollandicus, are only slime-forming varieties of this species. When cultivated at higher 

 temperatures on artificial substrates, they rapidly lose the power of forming slime. Most 

 of the strains of Sc. cremoris showed only slight power of resistance, and died oil' in course 

 of time; a few of the strains, however, were fairly resistant, and one (No. 18) has even 

 kept alive in agar stab for over three years without re-inoculation. This same strain had 

 previously distinguished itself in the butter manufacture, being found practically as a 

 [)ure culture in a dairy starter which had not l)een renewed for many years. 



Streptococcus cremoris is killed by heating to 65° — 70°. Its optimal temperature lies 

 below 30°, and the bacterium can, as is well known in practice, be trained to grow at fairly 

 low temperatures, so that it sours rapidly even at 15°. Very powerful strains (especially 

 those forming slime) may develop at 3°; others less strong will not grow at under 10°. 

 It does not generally grow at blood heat. In most strains, the maximal temperature lies 

 at 35°. 



Streptococcus cremoris rarely forms much over 7 "/qq lactic acid in milk. It can develoj) 

 such a quantity of carbonic acid that üne stripes appear in the curd (illustration of fer- 

 mentation test g. 2). Most strains have a certain power of dissolving casein; No. 15 

 has even formed over 20% SN. It does not thrive so well on artificial substrates as Sc. 

 lactis, and thus proves itself a more pronounced milk bacterium. In accordance with this, 

 we also find that among disaccharides, it attacks chiefly lactose, and prefers this sugar 

 at the concentration at which it is found in milk, or even higher. Saccharose is practically 

 speaking not fermented at all, and maltose, and thus also dextrin, only exceptionally 

 to any considerable extent. The best starters seem to have the least power of fermenting 

 these sugars. Some strains ferment salicin, others not. The three monosaccharides, lævu- 

 losc, glucose and mannose are on the whole fermented equally well. Alcohols and pentoses 

 are as a rule not attacked at all (with good nitrogen sources, there may be a slight sugges- 

 tion of fermentation of arabinose). 



In morphological respects, Sc. cremoris (PI. IV — IX) dilTers from Sc. lactis by forming 

 chains, often of considerable length, at optimal temperature, both in milk and broth. 

 The more powerful the bacteria, the thicker — and generally also longer — are the chains. 

 Weakened strains can, in broth, form chains so twisted and clustered together that they 

 may be mistaken for staphylococci (PI. VI, No. 18). On agar streak, the cells as a rule 

 assume a very abnormal appearance, becoming swollen, pointed, and often rod-shaped. 

 The rods can, however, in many cases be resolved into discs on further observation, and 

 then resemble woodlice or other articulata. On agar streak (at the optimal temperature), 

 we also often find division in the longitudinal direction of the chains. (PI. VIII, No. 20). 

 At maximal temi)erature, chain formation ceases (PI. IX, No. 2). In gelatin, the chains 

 are often short, and the cells (especially on AG) irregular. As regards slime formation in 

 milk, this is due to a slimy transformation of the highly swollen capsules, which may 

 be found in all lactic acid bacteria in a young state, but is particularly frequent in this 

 species. When the milk becomes so sour as to curdle, the slime formation ceases again. 

 No. 19 (PI. Vll) shows this development distinctly. If a stained preparation of the bac- 

 teria in the capsule stage be exposed to pressure, the streptococcus chains will burst out 

 from the capsules, appearing then as while worms. 



