256 



PHYSIOLOGY OF BACTERIA 



Assuming the colonies to be spherical, the total volume of all 

 on any plate is obtained by multiplying the number of colonies in 

 each group with the corresponding volume, and adding all volumina. 

 The result thus obtained is given in the lowest line of Table 72. 

 The control, without silver nitrate, had produced a total volume of 

 171 mm. 3 of bacteria. The maximum with AgNOa was 755 mm.^ 

 or 4.4 times as much. Since these last figures represent, at least 

 approximately, the volume of all bacteria produced in the same 

 amount of agar from the same amount of seeding, the only difference 

 being the presence of 0.00075 % AgNOs in the one medium, a great 

 influence of chemical stimulation upon crop production of bacteria 

 cannot be denied. 



Table 72. — Numbers and Sizes op Colonies of Bad. typhi murium, 

 ON Agar + AgNOa 



Hofmann mentions a large number of substances which 

 acted as stimulants in similar experiments. Among them 



