384 



RESPIRATION 



[CH. XXIV. 



sists of two fixed glass globes, C and F, the upper one communicating by means of 

 the stopcock, J>, and a stout indiarubber tube with another glass globe, L, which 

 can be raised or lowered by means of a pulley ; it also communicates by means of a 

 stopcock, B, and a bent glass tube, A, with a gas receiver (not represented in the 

 figure) ; A dips into a bowl of mercury, so that the gas may be received over 

 mercury. The lower globe, F, communicates with by means of the stopcock, E, 

 with /, in which the blood is contained by the stopcock, G, and with a movable glass 

 globe, Jf, similar to L, by means of the stopcock, H, and the stout indiarubber 

 tube, K. 



In order to work the pump, L and M are filled with mercury, the blood from 

 which the gases are to be extracted is placed in the bulb /, the stopcocks, H, E, I), 

 and B, being open, and G closed. M is 

 raised by means of the pulley until F is 

 full of mercury, and the air is driven 

 out ; E is then closed, and L is raised 

 so that C becomes full of mercury, and 

 the air is driven off. B is then closed. 

 On lowering L the mercury runs into it 

 from C, and a vacuum is established in C. 

 On opening E and lowering M , a vacuum 

 is similarly established in F-, if G is now 



B.B 



Fio. 388. L. Hill's Air-pump. 



FIG. 339. Waller's apparatus for gas analysis. 



opened, the blood in / will enter into ebullition, and the gases will pass off into 

 F and (7, and on raising M and then L, the stopcock B being opened and G closed, 

 the gas is driven through A, and is received into the receiver over mercury. By 

 repeating this operation several times the whole of the gases of the specimen of 

 blood is obtained, and may be estimated. 



The very simple air-pump (fig. 338) devised by Leonard Hill will be, however, 

 amply sufficient for most purposes. It consists of three glass bulbs ; (B.B.), which 

 we will call the blood bulb ; this is closed above by a piece of tubing and a clip, a ; 

 this is connected by good indiarubber tubing to another bulb, d. Above d, how- 

 ever, there is a stopcock with two ways cut through it ; one by means of which B. B. 

 and d may be connected, as in the figure ; and another seen in section, which unites 

 d to the tube e, when the stopcock is turned through a right angle. In intermediate 



