HANDBOOK OF PHYSIOLOGY. 



means of the stopcock, E, with /in which the blood is contained by the 

 stopcock, 6r, and with a movable glass globe, M, similar to />, 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. Mis raised 

 by means of the pulFey until F is full of mercury, and the air is driven 

 out. E is then closed, and L is raised so that (7 becomes full of mer- 

 cury, 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 C. On 

 opening E and lowering J/, 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 C, 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 repeat- 

 ing the experiment several times the whole 

 of the gases of the specimen of blood is 

 obtained, and may be estimated. 



A. 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 mercurial 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 ab- 

 sorbed by a liquid such as plasma would de- 

 pend upon the proportion of the gas in the 

 atmosphere to which the liquid is exposed 

 if the proportion is great, the absorption will 

 be great; if small, the absorption will be 

 similarly small. The absorption continues 

 until the proportions of the gas in the 

 liquid and in the atmosphere are equal. 

 Other things will, of course, influence the 

 absorption, such as the nature of the gas employed, the nature of the 

 liquid, and the temperature, but cceteris paribus, the amount of a gas 

 which a liquid absorbs depends upon the proportion the so-called par- 

 tial pressure of the gas in the atmosphere to which the liquid is 

 subjected. And conversely, if a liquid containing a gas in solution be 

 exposed to an atmosphere containing none of the gas, the gas will be 

 given up to the atmosphere until the amount in the liquid and in the 



FIG. 77. Ludwig's Mercurial 

 Pump. 



