Gases of the Blood 589 



Which, following the combinations, may give us the following 

 extreme total results: 



Carbonic acid __. 19 or 18.8 



Oxygen 9.6 or 9.4 



Let us add to this the quantity of carbonic acid contained in 

 the condensed water, and the direct measure may give us a result 

 for this gas which is below the truth, from 0.4 cc. to 0.6 cc. 



We must now double all these figures, to get the total quantity 

 of gas contained in 100 cc. of blood, the amount which is commonly 

 used; so that, in spite of the greatest precautions, and supposing 

 that the extraction of the gases has been perfect, it is impossible 

 to say that the number obtained is not too high or too low for the 

 oxygen and the nitrogen by 2 or 3 tenths, and for the carbonic 

 acid by nearly a unit. 



After that we can judge the value of these second and third 

 decimals, which the tables of analyses almost always display fol- 

 lowing their whole numbers. I am strongly inclined towards this 

 truth that, if the decimals are exact from the arithmetical point of 

 view, the number of units itself is false from the chemical point of 

 view, for to the different causes of error mentioned above, we 

 should add the imperfection of the apparatuses which most of the 

 operators use. 



And what is to be said now from the physiological point of view? 

 The analysis of which we have just spoken gives us, for a deter- 

 mined case, an absolute result, error excepted. But how many 

 things cause complications, if we wish to compare it to another 

 analysis made by the same experimenter, with the same instru- 

 ment, on another animal belonging however to the same species! I 

 have specified before the differences which, from the point of view 

 of the oxygen content, may be presented by the blood of an animal 

 placed in different conditions, as in digestion and fasting, etc. Since 

 then, MM. Mathieu and Urbain, repeating with the gas pump the 

 experiments which I had performed simply with carbon monoxide, 

 and which, consequently, applied only to oxygen, have multiplied 

 and varied the conditions in which the animals can be placed. 



