BACTERIUM TERMO. 



281 



FIG. 105. Swarmers of Ba- 

 ilis, after Fischer (x 



tiine. Preparations examined in the interim unite all stages of 

 germination. As a rule, the germinated rodlets at once set up 

 movement; they enter into the "swarm- 

 ing" or "roving" stage. Such a swarm- 

 ing rodlet still carries about at its hinder 

 end its spore-case. The number of the 

 " swarmers " becomes by successive 

 divisions continually greater, and they 

 fill the entire fluid before the beginning 

 of the formation of the pellicle. Then 

 for the first time the swarmers collect 

 on the surface of the fluid, come to rest 

 there, and produce the pellicle. The 

 rodlets are of unequal length, but for the 

 most part consist of two connected in- 

 dividuals. Their movement is quite 

 characteristic, flittering across the field 

 of view. Modern research has shown 



that the swarmers move by means of numerous cilia distributed 

 over their body (Fig. 105). 



Bacterium termo. The movement of the swarmers of Bacillus 

 subtilis under a cover-glass soon ceases ; and we may study this 

 phenomenon more advantageously upon the so-called Bacterium 

 termo (a general name rather than that of a particular species), 

 the constant accompaniment of numerous processes of decay. 

 We may reckon pretty well with certainty to find swarmers of 

 -this group in water in which peas or beans have been left to 

 rot. We can readily prepare a suitable culture if we take a drop 

 of this fluid and transfer it to a proper nutrient solution. For 

 such, Cohn's "normal solution " can be recommended; this con- 

 sists of 1 gram acid phosphate of potassium, 1 gr. sulphate of 

 magnesia, 2 grs. neutral acetate of ammonia, and Ol gr. calcium- 

 chloride dissolved in 200 c.cm distilled water. By repeated 

 transfer of infected drops into new culture fluid, a quite pure 

 culture may be obtained, if desired. In a few days the culture 

 fluid becomes rnilkily turbid, and forms then a greenish pellicle. 

 Microscopical investigation shows rod-like cells, of about 0*0015 

 mm. long, and from i to ^ that in breadth, in course of active 

 bipartition, and thence united in pairs, rarely in longer rows. 

 The movement is peculiarly jerky. Motionless individuals fill 

 the zoogloea, which ultimately forms a greenish slimy skin or 



