OXYGEN. 435 



comes into play. At this point we meet with great difficulties in our 

 search for knowledge. To answer this question we must know, in the first 

 place, exactly how great the gas tension in the tissues is. We know, from 

 the experiments of Strassburg, 1 what the oxygen tension of the lymph is, 

 and as this surrounds all tissues and cells of the body, we get some idea as 

 to the gas-pressure prevailing there. Strassburg found the oxygen ten- 

 sion of the lymph greater than one atmosphere. According to the general 

 conception, the oxygen tension in blood is less than one atmosphere. 

 If this be true, it is necessary to assume some special activity as the 

 cause of the giving up of oxygen to the tissues. On the other hand, Strass- 

 burg found that the tension of carbon dioxide in the lymph was less than 

 that of venous blood. From this fact we should speak of gas secretions 

 in the tissues. Some idea of the consumption of oxygen by the tissues 

 is obtained by tracing the oxygen tension of the blood in its transformation 

 from the arterial to the venous condition. 2 



The oxygen supply of the tissues may be regulated in quite a number of 

 different ways. The rate of the blood flow has an effect and again the 

 change of the content of the blood in hemoglobin, whether it be due to the 

 formation of new hemoglobin, or a relative increase by elimination of 

 plasma. By means of such changes combined with variations in the 

 intensity of work of the organs of respiration, -the animal organism is, 

 within certain limits, independent of quite considerable variations in 

 oxygen and carbon dioxide tensions. It is highly interesting that each 

 lung has its own independent gas-exchange, and yet is able to mutually 

 compensate the other. If there is a greater oxygen tension in the air 

 supply of one lung, then a greater absorption of oxygen takes place in 

 this lung than in the other. At the same time, the other lung absorbs 

 less. than the customary amount of oxygen, so that the total absorption 

 of oxygen by the two lungs remains about the same. 



If the partial pressure of the oxygen in the inspired air becomes lower, 3 

 then naturally that of the alveolar air becomes similarly affected. The 

 degree of change in the composition of the latter depends materially upon 

 the amount of oxygen absorption and the ventilation of the lungs. This 

 is an extremely important fact. It is for this reason that with the same 

 oxygen partial pressure, the alveolar air of two different individuals may 

 have a quite different composition, according as to whether one breathes 

 more deeply than the other, so that the lungs have a greater ventilation. 



1 Pfliiger's Arch. 6,. 65 (1872). 



2 Cf. Ch. Bohr: Handbuch d. Physiol. p. 196. Loewy and von Schrotter, Z. exper. 

 Path. u. Ther. 1, 197 (1905). 



3 Cf. Paul Bert: La pression barome'trique. Paris, 1878. Frankel and Geppert: 

 Ueber die Wirkungen der verdiinnten Luft auf den Organismus, Berlin (1883). A. 

 Loewy: Untersuchen iiber die Respiration und Zirkulation bei Aenderung des Druckes 

 und des Sauerstoffgehaltes der Luft, Berlin, 1895. 



