I. — PHYSIOLOGY. 161 



then, the actual quantity of oxygen in the blood on the two occasions 

 would be : 



Here, I am in my usual health. In the chamber, I vomited; my 

 pulse was 86 — it is now 56 ; my head ached in a most distressing fashion, 

 it was with the utmost difficulty that I could carry out routine gas 

 analyses, and when doing so the only objects which I saw distinctly 

 were those on which my attention was concentrated. 



In the anoxic type of anoxaemia there may then be quite a sufficient 

 quantity of oxygen in the blood, but a sufficient quantity does not avail 

 in the face of an insufficient pressure. Indeed, as I shall show 

 presently, the anoxic type of anoxaemia is the most serious. We are 

 therefore confronted with something of a paradox in that the most 

 severe tjrpe of anoxaemia is one in which there is not necessarily an 

 insufficient quantity of oxygen in the blood at all. 



And here let me justify fhe statement that the anoxic type is the 

 most to be feared. I can justify it on either or both of two grounds. 

 Firstly, of the thi^ee types it places the tissues at the greatest disadvan- 

 tage as regards oxygen supply, and secondly, it is of the three the least 

 easy type for the organism to circumvent. 



Let me dwell for a moment upon the efficiency of the blood as a 

 medium for the supply of oxygen to the tissue in the three types. The 

 goal of respiration is to produce and maintain as high an oxygen pres- 

 sure in the tissue fluids as possible. For the velocity of any particular 

 oxidation in the tissues must depend upon the products of the concen- 

 trations (active masses) of the material to be oxidised and of the oxygen. 

 Now the concentration of oxygen in the tissue is proportional to its 

 partial pressure, and the highest partial pressure in the tissue must, 

 other things being equal, be the result of that type of anoxaemia in 

 which there is the highest partial pressure in the blood plasma. 



It is interesting and not uninstructive to try to calculate the degree 

 to which the tissues are prejudiced by being subjected to various types 

 of anoxa3mia. Let us suppose that we have a piece of tissue, muscle for 

 instance, which normally is under the following conditions : 



(a) One cubic centimetre of blood per minute runs through it. 



(b) The total oxygen capacity of this blood is '188 c.c. of oxygen 



per c.c. of blood. 



(c) The percentage saturation is 97. 



(d) The oxygen pressure is 100 mm. 



(e) The oxygen used is '059 c.c. 



(f) The oxygen pressure in the tissues is half of that in the veins, 



in this case 19 mm. 



Compare with this a severe case of anoxic anoxasmia, one in which 

 the blood-flow is the same as above, and also the oxygen capacity value 

 of the blood, but in which the oxygen pressure is only 31 mm. and the 

 percentage saturation of tlie arterial blood 66 per cent. Let us further 

 'etain the assumption that the oxygen pressure in the tissues is half 

 1920 M 



