CHARACTERS OF LACTIC BACTERIA 275 



infants, but is often met with in milk, although rarely in 

 any abundance. The colonies on gelatine plates are 

 round, shining, white like porcelain, with smooth, circular 

 margins, and more or less hemispherical, standing up 

 from the surface of the plate. The bacteria from typical 

 cultures do not stain by Gram's method (see p. 8). Some 

 forms in this group very closely resemble Bacterium colt 

 (p. 1 06), and are difficult to distinguish from the latter 

 with certainty. Eckles' Bacillus No. 8, which gives a 

 pleasant, ripe cheese aroma in milk, and is a useful 

 " starter " for the butter-maker, appears to be a form 

 near Bact. lactis aerogenes. The Bacilli Guillebeau, 

 a and b (Freudenreich), obtained from milk of cows 

 suffering from inflammation of udder, and giving rise 

 to " gassy " or " blown " cheeses, are closely related to 

 Bact. I. aerogenes. In the same group there are included 

 many other bacteria, isolated from milk by various 

 workers, which differ slightly from the typical form 

 described above. Bact. limbatum, Marpmann, coagulates 

 milk but produces no gas. Bs. lactis innocuus, Wilde, 

 and Bs. No. 41, Conn, give rise to a little acid only, but 

 do not coagulate milk or develop gas in it. The latter 

 variety gives rise to a pleasant aroma in unsterilized 

 milk. Several varieties which have been isolated from 

 cheese should be included here. Very closely resembling 

 Bact. acidi lactici, Huppe, and therefore to be included 

 in the group is Bact. pneumonia of Friedlander, the cause 

 of pneumonia in man. It does not coagulate milk, but 

 forms gas. When taken from the body or from cultures 

 in milk the organisms exhibit well-developed gelatinous 

 capsules. The colonies on gelatine are round, moist, 

 and white, very similar to those of Bact. lactis aerogenes. 

 To the same group may be added Bact. lactis viscosum, 



