296 RESPIRATION 



to us by Dr. Parkes Weber, Douglas and I found that the haemo- 

 globin percentage was increased 80 per cent; the blood volume 

 IOO per cent; and the total haemoglobin 260 per cent; 35 and we 

 found similar increases in another case. Lorrain Smith had al- 

 ready found a considerable increase in a non-congenital heart 

 case with chronic cyanosis. 36 



In some cases (so-called idiopathic polycythaemia) where there 

 is neither exposure to a lowered oxygen pressure nor any heart 

 or lung affection, the haemoglobin percentage and number of 

 red corpuscles per unit volume is greatly increased. On determin- 

 ing the blood volume in two of these cases I found it greatly in- 

 creased. Boycott and Douglas examined three other cases with 

 a similar result. 37 In the most marked of these cases the haemo- 

 globin percentage was 1 76 per cent of the normal, and the blood 

 volume nearly three times the normal, so that the amount of 

 haemoglobin in the body was about five times the normal. Idio- 

 pathic polycythaemia is accompanied by a bluish tint of the skin, 

 and this suggests that from some cause there is slowing of the 

 circulation and consequent anoxaemia of the tissues, to which the 

 increased haemoglobin percentage is a natural response. 



It is clear that increase in the haemoglobin percentage will tend 

 to diminish the tissue anoxaemia at high altitudes or in cases of 

 heart affections; for the blood can pass more slowly (or at a more 

 normal rate at high altitudes) through the capillaries before a 

 given fall in the oxygen pressure occurs. This compensation is 

 never complete, however; for if it were there would be no stimu- 

 lus to the increased concentration of haemoglobin. An undue rise 

 of CO 2 pressure in the tissues is also prevented by the increased 

 haemoglobin percentage. 



When the red corpuscles and haemoglobin are increased 60 or 

 80 per cent the viscosity of the blood is very greatly increased, 

 and a good deal of stress has been laid on this increased viscosity 

 as a hindrance to circulation. Nevertheless persons with their hae- 

 moglobin percentage increased 50 per cent at high altitudes are 

 capable of the severest muscular exertion ; and there is no indica- 

 tion in them of any circulatory impairment. When we consider 

 the manner in which the circulation is normally regulated, as 



"The details of this case are given by Parkes Weber and Dorner, Lancet, 

 Jan. 21, 1911. 



38 Lorrain Smith and McKisack, Trans. Path. Soc. of London, LIII, p. 136, 

 1902. 



87 Boycott and Douglas, Guy's Hospital Reports, LXII, p. 157. 



