EFFECT OF EXTERNAL CONDITIONS ON BACTERIA 159 



on both sides, and is practically nothing in the ultra-violet or 

 in the red rays. The exact point where action begins and ends 

 differs with various forms, but generally it begins in the blue 

 end of the green and reaches a maximum in the violet, and 

 diminishes from the violet to the ultra-violet (Fig. 41). The 



FIG. 41. Plate of anthrax spores, exposed for 5 hours to the solar spectrum in 

 August, and incubated for 48 hours. The horizontal line shows the length of 

 the spectrum. The vertical lines are not FRAUENHOFER'S line, but serve to 

 show the limits of the principal regions of the spectrum. The clearest area is 

 that where fewest spores have developed in the incubation where, conse- 

 quently, the bactericidal effect was greatest. (From Ward, '94.) 



same kind of action is obtained by electric light, although, 

 of course, the energy is very much less. 



Electricity. A great deal of interest has been manifested 

 in the effect of electricity upon bacteria, and a great many 

 experiments have been performed to determine what this ei- 



