INFLUENCE OF TEMPERATURE 589 



tigators as well, to be 1.34 cubic centimetres of oxygen for 

 one gram of haemoglobin. 22 



If the course of the pressure curves, however, is more 

 closely inspected, marked differences will be noted on com- 

 parison of normal laked blood and solutions of isolated 

 haemoglobin obtained from different animal species and in- 

 dividuals, which have led Bohr and his followers to assume 

 the existence of a multiplicity of haemoglobins and particu- 

 larly to differentiate " haemochrome " from haemoglobin. 



As a matter of fact, the line of the tension curves may 

 be influenced by a number of physical and chemical factors. 23 



Influence of Carbonic Acid Pressure. As one of the most 

 important factors of this type we have come to recognize 

 carbonic acid. According to the studies of Bohr, Hassel- 

 bach and Krogh the ascent of the curve becomes the less 

 sharp the greater the quantity of carbonic acid in the blood. 

 Given the same oxygen pressure, there will be less oxygen 

 fixed the more carbonic acid there is present; this may be 

 expressed in other words by saying that carbonic acid may 

 raise the dissociation pressure of oxyhaemoglobin, that is, 

 increase its tendency to give off oxygen. We are here deal- 

 ing with a purposeful provision of the economy which makes 

 it possible to have an especially ready oxygen release from 

 the arterial blood at precisely such places where for any 

 reason carbonic acid accumulates in the tissues and where 

 a danger from oxygen impoverishment is threatened. 



Influence of Temperature. Another important factor in 

 connection with oxygen tension is the temperature (as shown 

 by the experiments of Paul Bert, Barcroft, Lowy and Cas- 

 pari). The power of taking up oxygen by haemoglobin is 

 diminished with increase of temperature. In increased 

 temperature from fever or from severe muscular exertion, 



22 Cf. Literature: 0. Cohnheim, Chemie der Eiweisskorper, III Ed., p. 343, 

 1911. 



23 Literature upon the Dissociation of Oxyhaemoglobin: Ch. Bohr, Nagel's 

 Handb. d. Physiol., 1, 57-68, 70-103, 1905; A. Lowy, Handb. d. Biochem., 4', 

 47-55, 1908. 



