54 EXTRACTION OF THE BLOOD-GASES. 



blood bulb (position x, a), or downwards through the lower tube (position 

 #', a'). This blood-bulb is first completely emptied of air (by means of a mercurial 

 air-pump), and then carefully weighed. One end (cc') of it is tied into an artery 

 or a vein of an animal, and when the lower stop-cock is placed in the position 

 (x a) blood flows into the receptacle. When the necessary amount of blood is 

 collected, the lower stop-cock .is put into the position, cc', a', and the blood- 

 bulb, after being cleaned most carefully, is weighed to ascertain the weight of the 

 amount of blood collected. The second part of the apparatus consists of the froth- 

 chamber, B, leading upwards and downwards into tubes, each of which is pro- 

 vided with an ordinary stop-cock, c and d. The froth-chamber, as its name 

 denotes, is to catch the froth which is formed during the energetic evolution of the 

 gases from the blood. The lower aperture of the froth-chamber is connected by 

 means of a well-ground tube with the blood-bulb, while above it communicates 

 with the third part of the apparatus, the drying -chamber, G. This consists of a 

 U -shaped tube, provided below with a small glass-bulb, which is half filled with 

 sulphuric acid, while in its limbs are placed pieces of pumice-stone also moistened 

 with sulphuric acid. As the blood-gases pass through this apparatus (which may 

 be shut off by the stop-cocks, e and/) they are freed from their watery vapour by 

 the sulphuric acid, so that they pass quite dry through the stop-cock, /. The 

 short well -ground tube, D, is fixed to/, and to the former is attached the small 

 barometric tube or manometer, y, which indicates the extent of the vacuum. From 

 D we pass to the pump proper. This consists of two large glass-bulbs which are 

 continued above and below into open tubes ; the lower tubes, Z and w, being 

 united by a caoutchouc tube, G. Both the bulbs and the caoutchouc tube contain 

 mercury the bulbs being about half-full, and F being larger than E. The bulb, 

 E, is fixed ; but F can be raised or lowered by means of a pulley with a rack and 

 pinion motion. If F be raised, E is filled ; if F be lowered, E is emptied. The 

 upper end of E divides into two tubes, g and h. of which g is united to D. The 

 ascending tube, h gas-delivery tube is very narrow, and is bent so that its 

 free end dips into a vessel containing mercury (v) a pneumatic trough and the 

 opening is placed exactly under the tube for collecting the gases, the eudiometer, 

 J, which is also filled with mercury. Where g and H unite, there is a two-way 

 stop -cock, which in one position, H, places E in communication with A, B, G, D 

 the chambers to be exhausted, and in the position, K, shuts off A, B, G, D, and 

 places the bulb, E, in communication with the gas-delivery tube, h, and the 

 eudiometer, J. 



B, G, D are completely emptied of air, thus : The stop-cock is placed 

 in the position, K ; raise F until drops of mercury issue from the fine tube, i (not 

 yet placed under J) ; place the stop-cock in the position H, lower F ; stop-cock in 

 position, K, and so on until the barometer, y, indicates a complete vacuum. J is 

 now placed over i. Open the cocks, c and b, so that the blood-bulb, A, communi- 

 cates with the rest of the apparatus, and the blood-gases froth up in B, and after 

 being dried in G pass towards E. Lower F, and they pass into E ; stop-cock 

 in position, K, raise F, and the gases are collected in J under mercury. The 

 repeated lowering and raising of F with the corresponding position of the stop- 

 cocks ultimately drives all the gases into J. The removal of the gases is greatly 

 facilitated by placing the blood-bulb, A, in a vessel containing water at 60C. 



It is well to remove the gases from the blood immediately after it is collected 

 from a blood-vessel, because the O undergoes a diminution if the blood be kept. 

 Of course, in making several analyses it is difficult to do this, and the best plan to 

 pursue in that case is to keep the receptacles containing the blood on ice. 



Mayow (1670) observed that gases were given off from blood in vacuo. Magnus 

 (1837) investigated the percentage composition of the blood-gases. The more 

 important recent investigations have been made by Lothar Meyer (1857), and by 

 the pupils of C. Ludwig and E. Pfliiger. 



