62 THE BACTERIA UNDER PHYSICAL AGENCIES 



algae, &c. all of which are more concerned with alterations of chemical com- 

 position must be added the influence of sunlight in diminishing the number of 

 bacteria. A critical review of the most important labours and researches per- 

 formed in respect of the self -purification of rivers is given by E. DUCLAUX (V.). 

 All the pathogenic Schizoinycetes seem to succumb under the influence of sun- 

 light. This has been shown by Arloing and Ward in respect of Bacillus anthracis; 

 Gaillard for B. typhi abdominalis ; Pansini for Vibrio cholerce asiaticce and a 



FIG. 29. Thickly-sown plate culture of typhus bacilli on agar-ayar. Covered with 

 paper letters and exposed to the sun's rays for ij hours, then kept twenty-four 

 hours in the dark, whereupon development of thickly congregated whitish 

 colonies was found ouly at the parts covered by the letters. (After H. Buclmer.) 

 Nat. size. 



fungus giving rise to white pus in wounds (Staphylococcus pyoyenes albus) ; 

 Chmiliewski for the organism which induces the formation of yellow pus (St. 

 pyojenes aureus), and the bacillus of erysipelas (Streptococcus erysipelatis) ; Hob. 

 Koch for Bacillus tuberculosis ; Charrin for the organism producing swine- 

 erysipelas ; and others. Most of the non-pathogenic fission fungi also succumb 

 to the influence of light. GALEOTTI (I.) arranged a number of chromogenic 

 species in the following descending series, the first member of which resists the 

 action of diffused daylight the longest : Bacillus ruber, Micrococcus prodiyiosus, 

 Sarcina rosea, Bacillus violaceus, B.pyocyaneus, B. lactiserythrogenes. According 

 to the researches of GKOTENFELT (I.), the last-named fission fungus does not 

 produce red colouring matter at all when strongly illuminated. K. DUBOIS (I.) 

 ascertained that the luminous bacterium, Photobacterium sarcophilum, found on 



