CHANGES OF THE BLOOD IN RESPIRATION. 153 



which interferes with the ordinary analysis of the blood for gases, it would 

 seem possible to extract all the oxygen by immediately saturating the blood 

 with carbon monoxide. The experiments of Bernard on this point are con- 

 clusive. He ascertained that by mixing carbon monoxide in sufficient quan- 

 tity with a specimen of fresh arterial blood, in about two hours, all the oxy- 

 gen which it contained was displaced. Introducing a second quantity of 

 carbon monoxide after two hours and leaving it in contact with the blood for 

 an hour, a quantity of oxygen was removed so small that it might be disre- 

 garded. A third experiment on the same blood failed to disengage any oxy- 

 gen or carbon dioxide. 



The view entertained by Bernard of the action of carbon monoxide in 

 displacing the oxygen of the blood is that the former gas has a remark- 

 able affinity for the blood-corpuscles, in which nearly all the oxygen is 

 contained, and when brought in contact with them unites with the haema- 

 globine, setting free the oxygen, in the same way that an acid entering into 

 the composition of a salt is set free by any other acid which has a stronger 

 affinity for the base. There is every reason to suppose that this view is cor- 

 rect, as carbon monoxide is much less soluble than oxygen and as it has 

 the property of disengaging this gas only from the blood, leaving the other 

 gases still in solution. In drawing the blood for analysis, Bernard took 

 the fluid directly from the vessels by a syringe and passed it under mer- 

 cury into a tube, in such a way that it did not come in contact with the 

 air. In this tube, which was graduated, the blood was brought in contact 

 with carbon monoxide, which displaced the oxygen from the corpuscles 

 and prevented the formation of carbon dioxide at the expense of a portion 

 of the oxygen. 



As carbon monoxide displaces the oxygen alone, it is necessary to resort 

 to some other process to disengage the other gases contained in the blood. 

 Modern experimenters, Ludwig, Lothar Meyer and others, have made use of 

 the mercurial gas-pumps, either of Ludwig or of Pfliiger, in which all the 

 gases of the blood are disengaged by removing the atmospheric pressure. 

 By means of a "froth-chamber," the gases can be collected and analyzed, 

 with but little loss of time ; but it is probable that there is always a slight 

 error in estimates, made in this way, of the relative proportions of oxygen 

 and carbon dioxide,. the proportion of oxygen being too small, and of carbon 

 dioxide, too large. Nevertheless, the results obtained by this method corre- 

 spond pretty closely with what is known of the nature of the respiratory 

 process ; and analyses of the blood taken at different periods show variations 

 in the quantities of oxygen in the arterial blood and of carbon dioxide in the 

 venous blood, corresponding with some of the variations which have been 

 noted in the loss of oxygen and gain of carbon dioxide in the air in respira- 

 tion. Nearly all the gases contained in the blood may be disengaged by 

 means of the gas-pump, but according to most observers, a small quantity of 

 carbon dioxide remains in the blood in combination. This may be removed 

 by the introduction into the apparatus of a small quantity of tartaric acid. 

 It was justly remarked by Bert, that as the apparatus for the exhaustion of 



