CHARACTERS OF LACTIC BACTERIA 271 



frequent, being found in almost all samples of cows' 

 milk. 



(a) Group i. The typical bacterium of this group, 

 is that which is known as Str. lacticus, Kruse, and is 

 the commonest of all forms occurring in milk. To it 

 most of the souring in the dairy is due. It appears to 

 be the same organism as : 



Bacterium lactis, described by Lister. 



Guntheri, L. & N. 



lactis acidi, Leichmann. 



lactis acidi^ I and 2 of Conn. 

 Lactococcus lactis, Beijk. 



The cells are usually slightly oval coc^i, .6 to I //, long, 

 and . 5 /a. broad, which before the process of division may 

 lengthen slightly, so that it is difficult to decide whether 

 they should be described as short bacteria or cocci. 

 They are mostly in pairs or short chains of four or five 

 together, hence the term streptococcus applied to them. 

 This species is somewhat anaerobic and forms very 

 minute colonies below the surface of gelatine plate 

 cultures. Under any circumstances the growth is very 

 slight on solid media, and the colonies are mostly round, 

 J to \ mm. in diameter, about the size of a small pin's 

 head, but may be oval or irregular in outline sometimes. 

 The organism stains with Gram's stain, and does not 

 produce gas when inoculated into fermentation tubes 

 containing broth and sugar. 



In milk it grows most rapidly at a temperature of 

 about 30 to 35 C, and the forms generally met with pro- 

 duce acid and curdling in six or eight hours, the curd being 

 dense and uniform, without gas bubbles and no separa- 

 tion of whey. Some varieties are slow in action at this 



