THE GASES OF THE BLOOD. 245 



elements are produced, and the blood conies into relationship with 

 the nascent cells in a way unknown in any other part of the body. 

 Further, various unusual elements, some like altered red cor- 

 puscles, others like white cells enveloping haemoglobin, are found 

 in this organ. 



The blood corpuscles, on coming to the spleen, are possibly sub- 

 mitted to a kind of preliminary test of general fitness, some 

 elements of the spleen pulp having the faculty of examining 

 their condition and deciding upon their fate. Many, no doubt, 

 pass the trial without any change, being found in good working 

 order. Others that are found totally unfit are broken up, and 

 their effete haemoglobin carried to the liver to be eliminated as 

 bile pigment. Some possibly undergo a form of repair, a white 

 cell taking charge of a weakly disk renews its stroma, adds to its 

 haemoglobin, and carries it through the final proof in the liver, 

 where it is chemically refreshed before going to the lungs for the 

 load of oxygen which it has to carry to the systemic capillaries. 



THE GASES OF THE BLOOD. 



These are present in two conditions; i.e., (1) dissolved in it 

 in accordance with well-established physical laws,* and (2) chem- 

 ically combined. But, since the latter are but loosely combined, 

 they may be separated by the same means as the former, and thus 

 the oxygen, carbon dioxide, and nitrogen, can all be removed by 

 reducing the pressure with the air-pump. For this purpose a 

 mercurial pump must be used, by means of which a practically 

 perfect vacuum can be formed, and all the gases obtained in a 



* I. A given liquid absorbs the same volume of a given gas independent 

 of the pressure exercised by that gas. 



II. At the same temperature the volume of a gas varies inversely with 

 the pressure, so that with twice the pressure a given volume of gas is 

 twice the weight. 



III. Therefore, the amount by weight of gas absorbed by a liquid de- 

 pends directly on the pressure, being nil in vacuo. 



The weight of a given volume of gas decreases as the temperature in 

 creases ; therefore, the amount of gas absorbed is in inverse proportion 

 to the temperature, being practically nil at boiling point. 



