CHARACTERS OF LACTIC BACTERIA 273 



produce acid without coagulation of milk. Str. hollandicus, 

 Scholl, found in the Dutch " lange Wei " (see p. 279), and 

 Micrococcus mucilaginosus, Mig., form slimy material. 

 There are others which set free slight amounts of gas 

 during fermentation, and are negative to Gram's stain. 

 To these may be added Str. mastitidis, Guill., a form 

 causing epidemic inflammation of the udder of cows, the 

 affected animals yielding small quantities of yellowish 

 milk : pure cultures coagulate milk and set free small 

 amounts of gas. Related to this group is the pathogenic, 

 Str. pyogenes^ Rosenbach, which sets up several inflam- 

 matory diseases in animals. 



(U) Group ii. The typical organism of this group is 

 that described by Hiippe, under the name of Bacterium 

 acidi lactici. It is widely distributed in milk but rarely 

 in any abundance, its development being probably checked 

 by organisms of the Str. lacticus type. The chief char- 

 acter distinguishing it from the bacteria of group i. is its 

 power of fermenting milk sugar and other carbohydrates, 

 with the production of considerable amounts of carbon 

 dioxide gas, often mixed with a little hydrogen. The 

 organism is always rod-shaped, but varies much in 

 length. Perhaps the average dimensions are I to I |-,u long, 

 and | to I/a, broad, the cells may, however, reach a length 

 of I o or 15 p and I J or 2 /x broad, and in certain media 

 undergo peculiar changes in form. They are usually 

 united in pairs, but some forms may appear as chains of 

 stumpy cocci. 



Bact. acidi lactici grows best aerobically and forms 

 rounded white, slimy colonies on the surface of gelatine 

 plates. They are often 5 or 10 mm. in diameter, much 

 larger and very different from the colonies of Str. lacticus. 

 The bacteria stain faintly with Gram's stain. When 

 ' s 



