117 



195 



crobaclcrium flavum develops an orange colour on the surface, and many tetracocci form 

 yellow, brown , orange or even red colours on the surface. 



37. The magnitude and appearance of the surface gro^^ih, as well as the formation 

 of colouring matter, are among the most variable qualities in the bacteria. 



38. \Vheii lactic acid bacteria are cultivated in milk, they are at their first stage of 

 development surrounded by a more or less distinct capsule. This can, under certain con- 

 ditions (in the case of the cocci only at lower temperatures) swell up and turn into slime. 

 The power of forming slime in milk is, however, very variable, and even though it may 

 occur more frequently in strains of one species than in those of another, it cannot be 

 used as species character. We have often encountered this power in Streptococcus cre- 

 moris and in the thermobacteria which form inactive lactic acid, and, in these cases, it 

 was always in strains of particularly strong Nitality. When, on the other hand, a strain 

 of one of the other species has temporarily proved sUmy, it has generally been defective 

 in one respect or another. 



39. The variations we have encountered in the lactic acid bacteria can as a rule be 

 explained as a further development of already existing tendencies, or more frequently, as 

 the result of weakness or degeneration. 



40. The manner in which a bacterium is inclined to vary is often one of the most 

 characteristic of all its qualities. 



41. In a bacteria culture, most of the individuals are but slightly resistant, and as a 

 rule Weakened in one or another respect, and it is therefore necessary to inoculate abund- 

 antly in order to make sure of transferring some of the individuals of unimpaired vitality, 

 which mark the culture as a whole. 



42. Consequently, next to unsuitable composition of the nutritive substrate, and too 

 high preservation temperature, the chief cause of the frequent degeneration met with in 

 laboraton.- cultures is the slight amount of the inoculating material generally used. 



43. As shown in my paper "The Main Lines in the Natural Bacteria System"', out of 

 the three morphological qualities of bacteria: shape of the cells, formation of spores, and 

 arrangement of the flagella, the last is the one which should primarily be used. For we find 

 that all bacteria which are able to live exclusively upon inorganic nourishment, and derive 

 their energy chiefly through simple oxygen processes, have the flagella terminally set, 

 whereas those requiring more complex organic food, and producing the more typical fer- 

 mentation processes, have the flagella distributed throughout the whole of the cell. On 

 this basis, therefore, I have divided the bacteria into two orders: Cephalotrichinæ and 

 Peritrichinæ. As the true lactic acid bacteria have no flagella, we cannot determine their 

 position in the system from their morphological qualities, but as they require as complic- 

 ated food as do the animals, there is no doubt that their place is in the order of Peritri- 

 chinæ. 



44. By taking the arrangement of the flagella together with the biological characters 

 as the first principle of division, we obtain within the same family of bacteria both sphe- 

 rical and rod forms, as well as screw forms, and the old generic names, which only express 

 the shape of the cells, are therefore no longer sufficient, but require to be supplemented 

 by various prefixes. If, in any exceptional instance, we use the old terms, then it will at 



