THE BLOOD. 



89 



same. Ludwig's pump, which may be taken as a type, is represented in 

 the figure. It consists of two fixed globes, C and F, the upper one com- 

 municating by means of the stopcock D, and a stout india-rubber tube 

 with another glass globe, L, which can be raised or lowered by means of 

 a pulley; it also communicates by means of a stop-cock, B, and a bent 

 glass tube, A, with a gas receiver (not represented in the figure), A dip- 

 ping into a bowl of mercury, so that the gas may be received over mercury. 

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

 with / in which the blood is contained by the 

 stopcock G, and with a movable glass globe, 

 M, similar to Z, by means of the stopcock, H, 

 and the stout india-rubber 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, D, 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 

 driven off. B is then closed. On lowering L 

 the mercury runs into it from C, and a vacuum 

 is established in 0. On opening E and lower- 

 ing M, a vacuum is similarly established in F; 

 if G be now 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, the gas is driven 

 through A, and is received into the receiver 

 over mercury. By repeating the experiment 

 several times the whole of the gases of the speci- 

 men of blood is obtained, and may be estimated. 



The Oxygen of the Blood. It has been 

 found that a very small proportion of the oxygen 

 which can be obtained, by the aid of the mer- 

 curial pump, from the blood, exists in a state of simple solution in the 

 plasma. If the gas were in simple solution, the amount of oxygen in any 

 given quantity of blood exposed to any given atmosphere ought to vary 

 with the amount of oxygen contained in the atmosphere. Since, speak- 

 ing generally, the amount of any gas absorbed by a liquid such as plasma 

 would depencl upon the proportion of the gas in the atmosphere to which 

 the liquid was exposed if the proportion were great, the absorption 

 would be great; if small, the absorption would be similarly small. The 

 absorption would continue until the proportion of the gas in the liquid 



FIG. 80. Ludwig's Mercurial 

 Pump. 



