CHAPTER VIII 



THE METABOLISM OF THE BLOOD ITSELF 



ONE of the subtler problems in physiology, and one which has 

 made a considerable appeal to some minds, is that of the extent to 

 which the blood itself can be regarded as a living organ of the body. 

 In some works blood is described as one of the " connective tissues," 

 the essential difference between it and for instance cartilage being 

 that the matrix is fluid instead of solid. This question brings us back 

 to a statement of what we regard as the essential criteria of life. 

 Without indulging in any general statement on the subject it is fairly 

 obvious that any tissue which we regard as alive must have a meta- 

 bolism of its own, and for that reason various workers have from time 

 to time tried to estimate the amount of oxygen used up by blood 

 per minute and the amount of carbonic acid given off by it. If such 

 a metabolism were proved to exist, it would be natural to discuss 

 the extent to which the plasma, the red corpuscles and the white 

 corpuscles respectively participated in it. 



The early work on this subject was of course wholly vitiated by 

 ignorance of the growth of microorganisms, the so-called metabolism 

 of the blood being simply evidence of bacterial action. 



Within the last few years, the problem has been taken up afresh 

 by two workers, Warburg (1) and Morawitz' 2 ', both at that time working 

 at Heidelberg, though in different laboratories. As will be seen they 

 worked from different points of view. 



Before describing their work in greater detail there is one point 

 which should be made clear. The oxidative processes in the blood, in 

 so far as they exist, are of two quite different natures which must 

 not be confused. In the first place there may be substances which 

 are readily oxidisable, which have found their way into the blood 

 in (small quantities from the tissues and which take up a certain 



