24 A MANUAL OF BACTERIOLOGY 



ozone or other germicidal bodies, the experiments of 

 Marshall Ward and others have conclusively shown that 

 germicidal action may be caused by the direct action of 

 the light, the violet and ultra-violet rays being those 

 concerned, and the red end of the spectrum has no effect. 

 Ultra-violet rays may produce mutations of the anthrax 

 bacillus (see p. 6). The Rontgen rays seem to have little 

 or no influence upon bacteria, but the results that have 

 been obtained are somewhat contradictory. 



The radium emanations with prolonged exposure and 

 near contact are germicidal to non-sporing organisms. 1 



Electricity, per se, has also usually little effect. When 

 the current is passed directly through the cultures electro- 

 lysis takes place, and the products formed may destroy 

 the bacteria ; currents of high potential, however, may 

 inhibit growth. 



Living motile bacilli are very sensible to induced currents 

 of electricity, immediately orientating themselves in the 

 direction of the current, while dead or paralysed bacilli are 

 unaffected. 



Bacterial Products 



The chemical changes produced by micro-organisms are 

 chiefly analytic or destructive the formation of simpler 

 from more complex bodies. This analytic faculty is 

 present to a marked degree in the process known as 

 putrefaction. Putrefaction is a term applied to the decom- 

 position of organic, especially protein, matter after the 

 death of the animal or plant. It is usually accompanied 

 by the evolution of foul-smelling gases and by solution 

 of the solid material. A large number of organisms are 

 concerned in this process, particularly a group to which 

 Hauser gave the name of Proteus. The first changes 

 which occur are the formation of proteoses and peptone, 

 1 See Green, Proc. Roy. Soc. Lond., vol. Ixxiii, 1904, p. 375. 



