Gases of the Blood 587 



Pierre. But I must speak of it, since I have happened, in some of 

 the experiments which are reported below, to compare analyses 

 of the blood of the carotid with analyses of the blood of the femoral. 

 I shall therefore repeat here what I have already said else- 

 where: 4 MM. Estor and Saint-Pierre have made no direct com- 

 parative experiment; if they had made even one, they would have 

 seen how mistaken their statement is. They have preferred to 

 search in books, and to compare results obtained by M. Claude 

 Bernard at different epochs, on dogs placed in the most varied gen- 

 eral conditions, using carbon monoxide as the means of extracting 

 the oxygen, with others for which they are indebted to several Ger- 

 man physiologists who used mercury pumps of different models, 

 and operated sometimes on dogs, sometimes on sheep. I showed 

 in detail, in the work quoted above, how truly faulty such a method 

 is ; if one can give the name of "method" to such a procedure. I 

 might today present the result of my own experiments, made 

 simultaneously on the same animal and with the same apparatus. 

 But I prefer to invoke the aid of two experimenters who have 

 studied these questions with what I consider an exaggerated preci- 

 sion, but which is a sure guarantee of painstaking in the experi- 

 ments. Now MM. Mathieu and Urbain, 5 investigating whether 

 there are differences in the blood of the various arteries, reached 

 the following results, in regard to the carotid and the femoral (page 

 192): 



Carotid— 20.45- 20.99- 15.06- 13.25- 12.75- 18.25- 15.00- 15.75- 14.93 

 Femoral __ 18.03- 17.69- 13.81- 13.25- 13.50- 18.00- 15.75- 15.75- 14.48 



We see, as the authors say correctly, that if there is a slight 

 difference in favor of the blood of the carotid, it is infinitely less 

 great than MM. Estor and Saint-Pierre claimed. Let us add that, 

 according to the experiments of MM. Mathieu and Urbain, the dif- 

 ference would increase greatly when, instead of taking arteries of 

 about the same caliber, one examines comparatively the blood of 

 the carotid and that of an artery of small dimensions, whether it 

 is close to or far from the heart.. But we cannot dwell on these 

 data; for our present purpose, it is enough for us to conclude that, 

 even if it is preferable to take the blood always from the same 

 artery, there is no serious disadvantage about taking it successively 

 from the carotid and the femoral, in the same animal, when one 

 is forced to it. 



Furthermore, before expressing ourselves on the importance of 

 the different causes of errors which may come from physiological 



