340 RESPIRATION 



arterial blood, a mean increase of 9.2 vols. per cent carbon dioxide, and a 

 deficit of 8.15 vols. per cent oxygen, or, after correcting for the venous stasis 

 caused by the catheter, + 8.2 C0 2 and 7.15 vols. per cent 2 respectively. 



E. THE DISTRIBUTION OF THE BLOOD GASES BETWEEN CORPUSCLES 



AND PLASMA 



The distribution of the blood gases between corpuscles and plasma has 

 been studied by Fredericq on the venous blood of the horse, and in this case 

 only the carbon dioxide was determined; 71.4 vols. per cent were found in the 

 plasma, 49.6 vols. per cent in the corpuscles. 



All other determinations along this line relate to defibrinated blood. The 

 following noteworthy facts have been recorded. Only traces of oxygen (0.10.2 

 vols. per cent) occur in the serum; almost the entire quantity belongs to the 

 blood corpuscles. We have already remarked that these traces can never be 

 entirely absent from the serum so long as the blood corpuscles contain oxygen 

 at all. 



The serum, on the other hand, contains most of the carbon dioxide. Ac- 

 cording to the investigations of Fredericq, Zuntz, and A. Schmidt, the carbon 

 dioxide of the serum amounts to about eighty-six per cent of the total quantity 

 in the blood. However, it is not impossible that by changes taking place in 

 the process of defibrination carbon dioxide might wander from the serum to 

 the blood corpuscles or from these to the serum. The observations of Ham- 

 burger indicate that in changing the quantity of gases in the blood, sub- 

 stances pass from the serum to the corpuscles and vice versa, and it is possible 

 that such migrations might occur in coagulation, as the result of which the 

 carbon dioxide carriers of the blood would probably become differently dis- 

 tributed between the corpuscles and the serum. 



When the whole blood is exposed to a vacuum, the entire quantity of 

 carbon dioxide escapes. Not so with the serum : it loses in a vacuum only a 

 part of its carbon dioxide, while a part can be driven out only by the addition 

 of acids. According to Pfliiger, the carbon dioxide firmly combined in the 

 serum amounts to five to nine vols. per cent. Since this portion firmly com- 

 bined is expelled in the presence of the blood corpuscles without the addition 

 of acids, there must be present in the corpuscles certain constituents which 

 act as an acid. 



FOURTH SECTION 



THE RESPIRATORY EXCHANGE OF GASES 



1. MECHANISM OF EXCHANGE BETWEEN BLOOD AND 

 ALVEOLAR AIR 



Knowing that the carbon dioxide exists in the blood in the form of a 

 dissociable compound independent of the partial pressure, it is reasonable to 

 suppose that the transfer of carbon dioxide from the blood to the alveoli of 

 the lungs takes place by the equalization of the existing difference in tension. 



