CHAPTER II 



THE GROWTH OF MASSIVE CULTURES OF 

 BACTERIA 



HAVING decided to study the chemistry of the bacterial 

 cell, it soon became evident that we must devise some way 

 of obtaining this substance in large quantity and fairly free 

 from admixture with foreign material. Bacteria had been 

 grown only in test-tubes, Petri dishes, and Roux flasks, 

 and none of these methods of growth gave the amount of 

 material necessary to promise any satisfactory investiga- 

 tion. As a medium, agar suits the purpose admirably, 

 because the bacterial growth can be detached and washed 

 from the surface of this medium quite free from admixture, 

 but it remained to devise some means of obtaining a large 

 surface so protected as to be guarded against contamina- 

 tion. At first we tried the Roux flasks, and by inoculating 

 one hundred of them with the colon bacillus, allowing the 

 cultures to grow for from two to three weeks at room tem- 

 perature, or for a shorter time in the incubating room, and 

 then washing off the growth with alcohol, we secured a 

 somewhat bulky and promising volume of bacterial, cellular 

 substance; but when this had been thoroughly washed 

 with sterile salt solution, extracted with alcohol and ether, 

 dried and weighed, we found the total yield, under the 

 most favorable circumstances; was not more than three 

 grams. This enabled us to make some preliminary experi- 

 ments and to demonstrate that the dead bacterial cells, 

 thus prepared, gave all the general color reactions for pro- 

 teins and were highly poisonous to animals, but the possi- 

 bility of making any satisfactory chemical study was not 

 promising. Moreover, the labor and care necessary to 



