Gases of the Blood 611 



sider the carbonic acid. The experiments of M. Fernet have in- 

 spired the belief that most of the carbonic acid of the blood (0.964) 

 is in the state of simple solution in the liquid, and that a rela- 

 tively small proportion (0.597) is alone in the state of combination. 

 Now what we have just said makes this interpretation of M. 

 Fernet's experiments rather improbable. If the larger part of the 



Fig. 32 — Percentage decrease of O and of CO 2 in the arterial blood when 

 the barometric pressure is diminished. 



carbonic acid was dissolved, the escape of the carbonic acid would 

 take place more easily and more regularly under the influence 

 of the decompression, and the graph C0 2 would be closer to the 

 bisecting line. Besides, we shall find in another part of this work 

 other reasons for thinking that the carbonic acid of the arterial 

 blood is, in the greater proportion, combined with carbonates and 

 phosphates, and that only a very small part exists in a state of 

 solution. However, these combinations are easily dissociated under 

 the influence of a decrease in pressure. 



These contradictions to the conclusions of M. Fernet do not 

 imply any criticism of his important work. For we must note that 

 the experiments of this physicist were made in vitro, and at a low 

 temperature, whereas mine had as instrumental apparatus the 

 living animal itself. The presence of tissues, the continual con- 

 sumption of oxygen, the multiplicity of surfaces of contact with 



