BY H. S. HALCRO WARDLAW. 515 



condition of anoxaemia which Haldane (1918) has described may 

 result. Such a condition might be produced by a conversion of 

 the oxyhemoglobin of the blood into its isomer methaemoglobin . 

 If in addition, there were decreased sensitiveness of the res- 

 piratory centre, such a condition might give rise to an appear- 

 ance resembling cyanosis, but to no dyspnoea. 



A third suggestion is that the colouration of the skin of in- 

 fluenza patients has nothing to do with the degree of oxygenation 

 of the blood, but that it is a direct pigmentation. In this case, 

 no respiratory disturbance would accompany the appearance of 

 the colour. 



If, as is supposed in the first hypothesis, the so-called cyanosis 

 is due to deficient aeration of the blood, then the oxygen content 

 of the arterial blood, and also of the venous blood, will be lower 

 than normal, provided that the rate of the circulation does not 

 increase out of all proportion to the metabolism. The amount 

 of carbonic and other acids in this blood, on the other hand, will 

 be abnormally high. Such blood will possess a normal capacity 

 for oxygen; its degree of saturation with oxygen, however, will 

 be abnormally low. The reaction or hydrogen ion concentration 

 of this blood will probably also be normal, since only an extreme 

 degree of acidosis affects the reaction. The reactivity of this 

 blood, however, or its power of neutralising added acid will be 

 abnormally low. 



On the second hypothesis the oxygen capacity of the blood 

 as well as its oxygen content will be altered. A given amount 

 of haemoglobin will not be able to take up its usual charge of 

 oxygen. The reactivity of this blood toward alkali will also 

 be diminished owing to the accumulation of acid products of 

 metaboLism . 



On the third hypothesis the blood will differ neither as regards 

 its degree of oxygen saturation nor its oxygen capacity from 

 normal, and its reactivity toward alkali will also lie within 

 normal limits. 



An investigation which has been carried out by Harrop (1919) 

 supports this last hypothesis. This worker found that the 

 venous oxygen content and the oxygen capacity of the blood 

 of influenza patients remained normal until the final stages of 

 the pneumonic complications were reached. The oxygen capacity 

 and the degree of saturation then began to diminish, and some 

 cases reached very low values before death took place. Harrop 



