CHAPTER III. 



VITAL PHENOMENA OF BACTERFA MOTION, HEAT 

 AND LIGHT PRODUCTION CHEMICAL EFFECTS. 



Motility. Many bacteria when examined under the 

 microscope are seen to exhibit active movements in 

 fluids. This motility is produced by the fine hair-like 

 flagella attached to all motile species. The movements 

 are of a varying character, being described as creeping, 

 waddling, rotary, undulatory, sinuous, snake-like, etc. 

 At one time they may be slow and sluggish, at another 

 so rapid that any detailed observation is impossible. 

 Some bacteria are very active in their movements, dif- 

 ferent individuals progressing rapidly in different direc- 

 tions, while with many it is difficult to say positively 

 whether there is any actual motility or whether the 

 organism shows only molecular movements so-called 

 " Brownian " movements a dancing, trembling mo- 

 tion possessed by all finely divided organic particles. 

 If in doubt in such cases it is best, wkeVe the matter is 

 of importance and one is skilled in the technique of 

 staining, to stain the organisms for flagella, and also to 

 examine them in a 0.1 per cent, bichloride of mercury 

 solution, when, if the movements continue, they are 

 purely molecular. Not all species of bacteria which 

 have flagella, however, exhibit at all times spontaneous 

 movements; such movements may be absent in certain 

 culture media and at too low or too high temperatures, 

 or of either an insufficient or excessive supply of oxygen. 



