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MANUAL OF BACTERIOLOGY. 



rises, and, little by little, cuts off the inflow of gas through 

 this tube. The flow is never completely cut off, as there is a 

 capillary opening in the tube considerably above any point to 

 which the mercury could possibly rise, which will always allow 

 the flow of a small quantity of gas (Fig. 25, b). This diagram 

 also shows a modification of the simple form of regulator, in 



Fig. 23. — Reichert's Gas- 

 regulator. 



Fig. 24. — Mercurial Gas-regulator. 

 a. Chamber containing volatile hy- 

 drocarbon, b. Capillary opening. 



the shape of a partition which divides off a lower chamber, 

 which contains mercury and is connected with the upper part 

 by a glass tube. The purpose is to make use of the elastic 

 properties of some volatile fluid, like ether, which floats on the 

 surface of the mercury at a. 



A most satisfactory gas regulator is that of Roux. It is 

 constructed entirely of metal, and its operation is due to the 



