I go Theobald Smith 



forces much of the fluid into the bulb. As soon as the lid is removed 

 the fluid returns to its former place in the closed branch with the excep- 

 tion of a small space at the top which is occupied by air originally dis- 

 solved in the liquid and driven out by the boiling. This air bubble 

 should be tilted ont. After the second boiling some air may still be 

 present. If this be tilted out the fluid will be found entirely free from 

 air after the third or last boiling. 



PHENOMENA OF ANAEROBIOSIS AND REDUCTION. 



For the cultivation of bacteria the fermentation tube con- 

 sists of two quite distinct portions sharply demarcated at the 

 place indicated by the line xy in fig. i. The bulb contains 

 fluid in direct communication with the air while the fluid in 

 the closed branch is almost entirely shut off from any such 

 communication. Moreover, during the process of sterilization, 

 the fluid in the latter has been entirel3- freed of air, as de- 

 scribed above. This oxygen-free condition of the fluid is very 

 clearly demonstrated by the following simple experiment : 



If to peptone bouillon be added a few drops of a concen- 

 trated aqueous solution of litmus, methylene blue or indigo- 

 carmine, and fermentation tubes be filled with this colored 

 fluid and sterilized, the fluid will be decolorized during the 

 boiling by reducing processes due to the organic substances in 

 the peptone bouillon "'-. In the open bulb the presence of air 

 very speedily causes a return of the color. In fact it may not 

 completely disappear at any time. If the tubes containing 

 the colorless, reduced litmus or methylene blue Ise allowed to 

 stand in a place sheltered from sudden changes of tempera- 

 ture, the fluid in the closed branch remains free from color 

 (with perhaps a faint indication of color near the connecting 

 tube) until the time arrives when the fluid in the bulb has 

 evaporated and a bubble of air escapesinto the closed branch, f 



* I at first conceived the reducing action due to the glucose only, but 

 the same process went on in peptone bouillon free from glucose. It is 

 not due to simple boiling, however, for litmus or other coloring matter 

 contained in simple bouillon or in water with or without a little Na^COj 

 remains unchanged in the sterilization. It is thus dependent on the 

 presence of glucose or peptone. 



fThis occurrence is like the escape of air into the reservoir of a stu- 

 dent lamp which brings about the continuous feeding of the wick with 

 oil. 



