35 AGRICULTURAL BACTERIOLOGY. 



produce branches. True bacteria are not supposed to branch 

 and, if this branching does actually exist, it suggests that the 

 tubercle bacillus is not a bacillus at all, but belongs to a dif- 

 ferent group of fungi. It has in short been claimed by so'mc 

 recent microscopists that the organism is not a bacterium but 

 belongs to a different class of plants and that, consequently, the 

 name Bacillus is a misnomer. These facts have not yet been 

 fully settled, and it is hardly possible to-day to state whether 

 the claim is correct or not. At all events the name bacillus 

 has become so firmly fixed to this organism that it is doubtful 

 whether it will be abandoned, even though it should be later 

 recognized that the organism has relations with other plants 

 than the bacteria. Moreover, according to the most recent 

 classification (see page 27) it should be called a Bacterium 

 rather than a Bacillus, if it be retained among the Bacteria. 

 But the term Bacillus is almost certain to stick to it, and in our 

 discussion we shall continue to use this name, at the same 

 time recognizing that its right to be called a bacillus is in some 

 doubt. 



Conditions of Life. This bacillus has somewhat limited 

 conditions under which it can grow. The temperature limits 

 within which its development is possible are quite narrow. 

 At first it was stated that it demanded a temperature between 

 96 and 105 F., but wider experimenting has shown that it 

 will grow at much lower temperatures, even as low as 84 F. 

 At these low temperatures it grows much more slowly than 

 at the higher temperatures. At first it was supposed that it 

 would not grow in any artificial media which could be pre- 

 pared in the laboratory. In his original experiments Koch 

 was obliged to use coagulated blood serum as a culture 

 medium. But on this point, too, wider experimenting has 

 extended the possibilities. It is now found that it can live 

 and flourish in a variety of culture media, provided that a 

 certain amount of glycerine is added. It was at first said 



