APPARATUS, MATERIAL, AND REAGENTS. 39 



contain mercury. The regulator is fixed in the 

 roof of the incubator, so that the bulb projects 

 either into the interior of the incubator or into 

 the water chamber. When the incu- 

 bator reaches the required temperature, 

 the mercury is forced up by means of 

 the screw in the lateral arm, until it 

 closes the orifice, at the extremity of 

 the vertical portion of the T. The gas 

 which passes through the lateral orifice 

 is sufficient to maintain the apparatus 

 at the required temperature. If the p IG . 22 . 

 temperature of the incubator falls the ^SaSS^ 

 mercury contracts, and gas passing REGULATOR - 

 through the terminal orifice of the T, increases 

 the flame of the burner and the temperature is 

 restored. 



Page's Thermo - Regulator resembles the 

 above, but instead of the T piece there are two 

 pieces of glass tubing. The outer tubing envelopes 

 the upper part of the stem of the regulator, and 

 admits of being raised or lowered. The upper end 

 of this tubing is closed by a cork, which is perforated 

 to admit the narrow glass tubing, which represents 

 the vertical arm of the T passing within the stem of 

 the regulator. This has a terminal and a lateral 

 opening, and is the means of entrance for the gas. 

 This regulator is adjusted by noting when the 

 thermometer indicates the desired temperature, and 

 then pushing down the outer tube until the terminal 



