SUGAR IN" THE NUTRIENT MEDIUM. 



155 



for such a long time in physiological and pathologi- 

 cal chemistry. 



The tubes, which should have the shape shown in 

 Fig. 12, are filled with one-per-cent grape sugar pep- 

 tone bouillon and sterilized in the 

 steam chamber. After inoculation 

 with a platinum loop in the incubat- 

 ing chamber the following facts de- 

 velop : 



1. If the opacity is produced only 

 in the open spherical part of the flask, 

 we have to deal with an aerobic va- 

 riety; if produced only in the closed 

 tube and the globe remains clear, we 

 have to deal with an anaerobic variety. 



2. The daily amount of gas pro- 



, , . , , .., . , . ., ,. FIG. 12. Fermen- 



duced is marked with ink ; it the call- tation Flask . 

 bre of the tube is known, we are able 

 to state, after the formation of gas has ceased on 

 the fourth to sixth day, what percentage of gas was 

 produced on each day. 



3. A rough analysis of the gas should be made. 

 After the amount of gas has been noted, we fill the 

 open sphere completely with ten-per-cent soda lye, 

 close it firmly with the thumb, and shake it for a 

 while. At the end of two minutes all the gas is al- 

 lowed to pass into the closed tube, and after the 

 thumb is removed the new volume of gas is read off. 

 The part which has disappeared is carbonic acid, the 

 rest is nitrogen, hydrogen, and marsh gas. The quan^ 

 titative analysis of these gases is best done by means 

 of Hempel's gas pipettes (vide Winkler: "Lehrb. 

 d. techn. Gasanalyse, " Freiburg, 1892) . The method 



