572 SAMUEL H. HUKWITZ 



the supply of oxygen to the tissues is beyond the immediate requirement. 

 In anemia, when the hemoglobin content is low and the volume per cent 

 of oxygen is correspondingly diminished, the consumption of oxygen re- 

 mains normal, or may even be above the normal. Many views are held 

 concerning the compensatory mechanism at work. 



It has been suggested that a more liberal supply of blood to the tissues 

 may be favored by a greater respiratory volume. Such an increase in 

 the depth of respirations has been noted by Jiirgensen, and Kraus(fr). 

 But since the tension of oxygen in the alveolar air of anemic individuals is 

 normally sufficient to saturate about 96 per cent of the hemoglobin in 

 the blood, it is difficult to see that much would be gained by increased 

 pulmonary ventilation. 



Nor has it been determined that the respiratory compensation in 

 chronic anemia resides in the blood itself. It was at one time thought that 

 the hemoglobin of anemic blood might differ from that of normal blood in 

 its power to carry oxygen. Such a conception, however, has been rendered 

 improbable by a comparison of the specific oxygen capacity of normal and 

 anemic bloods (Butterfield, Peters). 



There are two other ways in which the anemic patient may carry on 

 his gaseous metabolism in spite of a marked reduction in hemoglobin. 

 Either the rate of the circulation is increased (Mohr(e), Plesch(a)), so 

 that the diminished amounts of hemoglobin are used more frequently for 

 transporting oxygen, or else the oxyhemoglobin which reaches the tissues 

 gives up unusually large amounts of oxygen, the blood returning to the 

 heart in various degrees of asphyxia (Kraus, Mohr, Morawitz). 



It has not as yet been determined with, certainty which of these two 

 methods is the more important in the chronic anemias of man. By an 

 indirect method of determining the total blood flow in man, Plesch 

 found that this was always increased in anemias in approximate propor- 

 tion to the severity of the anemia. According to his view, the anemic indi- 

 vidual compensates for his lack of hemoglobin almost entirely by main- 

 taining a more rapid circulation. Some objection to this view has come 

 from the observation that it is uncommon to encounter marked hyper- 

 . trophy of the heart even after long-continued severe anemias, which 

 would be the case if the heart continually did an increased amount of 

 work. 



Concerning the degree to which the hemoglobin gives up oxygen to the 

 tissues of anemic patients, there is likewise considerable difference of 

 opinion. Mohr found a marked reduction in the oxygen content 

 of venous blood taken from animals that had been rendered anemic by 

 hemorrhage, indicating that the hemoglobin had given up an unusually 

 large prooprtion of its oxygen during its passage through the tissues. A 

 similar observation was made by Morawitz and Rb'hmer, whereas Plesch 



