n8 



BACTERIOLOGY 



by a ground glass stopper, which also closes the top of the outer 

 chamber, D. In the ground surface of this stopper a gamma- 

 shaped (r) groove is cut, the vertical limb extending from the 

 lower tip of the stopper to the level of the opening, O. The 

 horizontal limb is deep where it joins the ver- 

 tical, but gradually becomes shallow and ends 

 about one-quarter the way around the stopper. 

 This groove serves for passage of the gas from 

 the inner tube BC, to the opening O, and thus 

 to the outer chamber D, and by rotating the 

 stopper, the amount of gas flowing through 

 this passage may be reduced to any desired 

 point. The outlet tube, H, leads from the 

 chamber D to the burner connection. 



The capillary, EF, leads to a bulb of suffi- 

 cient size; the larger the more sensitive the 

 instrument. Either the large bulb with inside 

 capillary, J, to be filled with mercury and 

 alcohol, or the smaller simple bulb for mercury 

 alone may be used. A side arm is attached 

 to one side of the capillary EF, for conveni- 

 ently controlling the height of the mercury 

 column. Either the curved capillary tube 

 with stopcock and a cup on the end, or the 

 simple tube with metal screw cemented in, 

 may be used here, according to the purpose 

 which the regulator is to serve. These parts 

 FIG. 48. Mac Neal are s i m ii ar to those of Novy's modification of 



gas-regulator. 



the Reichert regulator. 



To fill the instrument, the air is partly driven out by heating 

 the bulb and then the desired liquid is drawn in by cooling, 

 repeating the heating and cooling until the instrument is full 

 of the liquid. For the small bulb, mercury is always used alone. 

 The large bulb, on the other hand, is filled first with either ether, 

 alcohol or toluol, and then part of this liquid is forced out by 



