? 



Na D 



59 O rrifl 



SERRATIA 

 MARCESCENS 



STREPTOCOCCUS 

 700' mu 



TOBACCO 

 MOSAIC 

 200x2 nifl 



RICKETTSIA 



PROWAZEKI 



300 m/l 



PSITTACOSIS 

 275 mju 



VACCINIA INFLUENZA GOLD SOL YELLOW FOOT-and- HAEMOGLOBIN 



MSmfJ 90/72/y SO mu FEVER MOUTH 3m^ 



22 mjj 



\0 m/1 



Relative Sizes of some Common Bacteria and Viruses. 



