76 SEPARATION OF THE GASES OF THE BLOOD. 



of water absorbs 0.02477 volume of air, consisting of 0.00862 volume of oxygen 

 and 0.01615 volume of the nitrogen. It accordingly contains 34 per cent, of 

 oxygen and 66 per cent, of nitrogen. Water, therefore, absorbs from the atmos- 

 pheric air an amount of gas that is by percentage richer in oxygen than the air 

 itself. 



SEPARATION OF THE GASES OF THE BLOOD. 



The expulsion of the gases of the blood and their collection for chemical 

 .analysis are effected by means of the mercurial air-pump. The Pfluger 

 pump for the extraction of gases is illustrated diagrammatically in Fig. 20. 

 It consists of a blood-receptacle (A), a glass flask with a capacity of from 250 

 to 300 cu. cm., drawn out above and below into tubes, each of which can be 

 closed by means of a stop-cock (a b). The cock b is an ordinary stop-cock, while 

 the cock a has a channel passing through its longitudinal axis and opening at x 

 in such a manner that in accordance with its adjustment it leads either into the 

 receptacle (position x a) or downward through the lower tube (position x' a') . 

 This receptacle is first completely deprived of air by application to a mercurial 

 air-pump and is then weighed. Next, the extremity x' is tied in an artery or a 

 vein of an animal and by placing the lower cock in the position x a the blood is 

 permitted to flow into the receptacle. When the desired amount has been col- 

 lected the lower cock is again placed in the position x' a', the exterior is carefully 

 cleaned and the receptacle is weighed in order to determine the weight of the 

 blood collected. 



The second portion of the apparatus is the froth-vessel chamber (B) , likewise 

 drawn out above and below into tubes, which can be closed by means of the 

 cocks c and d. The purpose of the froth-chamber is to take up the froth formed 

 in consequence of the active escape of the gases from the blood. Below, the froth- 

 chamber is connected with the receptacle by means of a ground-glass tube and 

 above likewise through a well-fitting tube with the drying apparatus (G). This 

 consists of a U-shaped tube expanded below into a glass bulb. The latter is half 

 filled with sulphuric acid, while each arm contains bits of pumice-stone saturated 

 with sulphuric acid. In passing through this apparatus, which likewise may be 

 closed by means of the two stop-cocks e and f, the gases of the blood yield up 

 their watery vapor to the sulphuric acid, so that they may be conveyed through 

 the cock f in a perfectly dry state. 



The short tube D is similarly connected with the prolongation from f by 

 means of a properly ground surface, and it is provided with a small manometer 

 from which the degree of vacuum can be read. The tube D communicates with 

 the pump -apparatus proper. This consists of two large glass flasks, E and F, 

 terminating above and below in open tubes, the lower of which, Z and w, are 

 connected by means of a rubber tube G. Both flasks and the tube are filled with 

 mercury to about half the height of the flasks. The flask E is secured, while the 

 flask F can be raised and lowered by means of a pulley-apparatus attached to a 

 stand. When F is raised E becomes filled, and when F is lowered E is emptied. 

 The upper extremity of E divides into two tubes, g and H, of which g is connected 

 with D. The tube h, passing upward, becomes greatly narrowed and further on 

 is so curved that its free extremity, i, dips into a basin containing mercury, v, 

 with its opening below the tube for the reception of the gases, J (eudiometer- 

 tube) completely filled with mercury. At the junction of g and H there is a cock 

 with a double channel, which in the position H connects the flask E with A B G D, 

 and in the position K closes A B G D and connects the flask E with the tube J. 



In the first place, B G D is completely exhausted of air by the following steps: 

 The stop-cock is placed in the position K; and F is raised until globules of mercury 

 pass from the free tube i, which is as yet not placed below J, into the basin. Then 

 the stop-cock is placed in the position H, when F is depressed. Next, the cock 

 is placed again in the position K, and so on, until the manometer y indicates 

 that evacuation has taken place. Now, J is placed over i. If the cocks c and b 

 are opened, so that the receptacle A communicates with the remainder of the 

 apparatus, the gases of the blood pass actively into B, with the generation of foam, 

 and through G, dried, to E. The depression of F brings them principally into E. 

 Finally, the cock is placed in the position K, while F is raised, and the gases are 

 conveyed to J above the mercury. Repeated depression and elevation of G with 

 appropriate adjustment of the cock will finally bring all of the gases into J. 



The removal of the gases from the blood is materially facilitated by placing 

 the recipient A in a vessel containing water at a temperature of 60 C. It is 



