Theories and Experiments 249 



carbonic acid of the blood and the oxygen of the air, an exchange 

 regulated by the laws of physics. 85 . 



The work of M. Fernet made them change their minds. This 

 physicist, by a series of experiments carried on with unusual 

 shrewdness, showed that carbonic acid and oxygen are kept in the 

 blood chiefly by a chemical affinity. The method of demonstration 

 which he used is directly connected with our subject, since he 

 utilized the effect of changes in the barometric pressure. 



The method used by M. Fernet involved removing from the 

 blood the gases which it contained, agitating it in closed vessels, 

 with oxygen or carbonic acid under various pressures, and meas- 

 uring the quantity of gas which it absorbed under these different 

 conditions. 



He thus showed that: 



The volumes of oxygen chemically absorbed and independent of 

 the pressure have a relative value so great that these experiments 

 are immediately distinguished thereby from those which relate to 

 saline solutions and even to serum. Not only is the progress of the 

 phenomenon almost completely freed from the law of simple solution, 

 but the volumes absorbed seem from the very first to be independent 

 of the pressure, since the volume, when chemically combined, is 

 almost five times as great as the volume when dissolved under atmos- 

 pheric pressure. (P. 209.) .... 



In respiration, the oxygen of the air exerts a pressure which 

 amounts to only one-fifth of the pressure of the atmosphere, so the 

 volume dissolved in the blood of the respiratory apparatus must be 

 reduced in the same proportion. The volume of oxygen absorbed in 

 the state of combination by the corpuscles will then become about 

 twenty-five times as great as the volume which actually enters the 

 serum in the state of true solution. (P. 211.) 



From this well established fact, in his actual experimental 

 conditions, M. Fernet thought he could draw the following con- 

 clusion: 



This is the explanation of this result, already verified by a great 

 many observations, that the absorption of oxygen is practically the 

 same, on the summits of mountain and on the plains, whatever the 

 atmospheric pressure; however, observation, here agreeing with 

 theory, has already noted slight differences corresponding to differ- 

 ences in pressure; but they can be demonstrated only by measuring 

 methods capable of great accuracy. (P. 211.) 



We should make reservations about this conclusion, which does 

 not seem to us to be included in the experimental premises. But 

 we shall see that certain physiologists let themselves be drawn 

 far beyond that. In this number is Longet. 



