98 BACTERIOLOGY. 



The instrument most commonly employed, the appar- 

 atus of Moitessier (Fig. 19), is based on somewhat the 

 same principles as the large regulators seen at the manu- 

 factories of illuminating gas, Avhich act very well when 

 employed on the large scale, as one sees them there; 

 but which, when applied to the limited and sudden fluc- 

 tuations seen in the gas coming from an ordinary gas- 

 cock, are practically useless. They are too gross in their 

 construction, and are only seen to act under compara^- 

 tively great and gradual fluctuations in pressure. If a 

 good form of thermo-regulator is employed, there is no 

 necessity for the use of any of the forms of pressure- 

 regulators thus far introduced. 



