9 o 



MANUAL OF BACTERIOLOGY. 



passing through the magnet is broken by the excursion of the 

 end of the thermoregulator away from the set-screw at b, 

 the armature is pulled away from the magnet by a coiled spring. 

 Another important precaution is that the points at which con- 

 tact is made and broken, b and c, should be tipped with plati- 

 num. A small piece of platinum 

 wire inserted into the ends of the 

 set-screws and a few square 

 centimeters of platinum foil 

 riveted to the opposite point of 

 contact meets the requirements. 

 If platinum is not used at these 

 points oxydation takes place and 

 prevents contact. The set-screw 

 at b is set by experiment for 

 the temperature desired. The 

 further the point of the set- 

 screw projects toward the free 

 arm of the regulator, the higher 

 the temperature maintained. 



CULTIVATION OF ANAEROBIC 

 BACTERIA. 



FIG. 28. Arrangement of tubes 

 for cultivation of anaerobes by 

 Buchner's method. 



The cultivation of anaerobic 

 bacteria is done best in a medium 

 containing i to 2 per cent, of 

 dextrose. The tube should con- 

 tain a large quantity of the 



culture-medium. Just before using, the medium should be 

 boiled for a few minutes. Inoculate the tube after cooling, 

 but while the medium is fluid. Anaerobes may be cultivated 

 in the closed arm of the fermentation-tube (see Fig. $f, but 

 the opening between the two arms of the tube must be small. 

 Buchner's Method jor the Cultivation of Anaerobes. Into a 



