ACTION OF LIGHT ON MICRO-OKGANISMS 



361 



■colonies made their appearance, whilst that portion of 

 the culture material which the sun's rays had reached 

 through the cut-out letters was sterile, or nearly so. 

 Buchner's paper is accompanied by a drawing copied 

 from a photograph representing such a circular dish in 

 which the cut-out letters formed the word ' TYPHUS,' 

 .and the sharpness of their contour is remarkably strik- 



V 



■^ / 



*-'/ 



■^ ' 





Fig. 22. — Typhoid Bacilli in Agae-agae, exposed to dieect 



Sunshine for One Houe. 



(After Buchner.) 



ing. In order to obtain such sharp pJiotobacteriographs, 

 ^s we propose to call them, Buchner points out that 

 the culture material must be thickly sown with the par- 

 ticular bacteria, so ^that the resulting colonies shall 



