408 



THE RESPIRATION 



air: thus, in one case, inspiration of air containing 11.4 per cent C0 2 only 

 served to increase the minute volume of air breathed from 10 to 14 liters, 

 with mild symptoms of dizziness and nausea (R. W. Scott). In a normal 

 person a much lower percentage of C0 2 would increase the pulmonary 

 ventilation several times over the normal and the symptoms would soon 

 become intolerable. The most probable explanation for the existence 

 of these conditions is that the interference with the pulmonary func- 

 tion has prevented proper removal of free C0 2 from the blood, to com- 

 bine with which the alkali has increased probably by diminution in its 

 excretion by the kidney. The increase in alkali raises the buffer action 

 of the blood for C0 2 . Oxygenation of the blood is also interfered with, 

 causing cyanosis. 



THE OXYGEN REQUIREMENT OF THE TISSUES 



In order to ascertain the average 2 requirement of the different tis- 

 sues of the body, it is necessary to adopt as a standard of measurement 

 the amount of 2 in c.c. absorbed per gram of tissue per minute. To ob- 

 tain it we must know: (1) the weight of the particular organ or tissue 

 under investigation; (2) the bloodflow through the vessels of the organ 

 in c.c. per minute; and (3) the different percentages of 2 in the arterial 

 and venous blood of the tissue. It would be beyond the scope of this 

 book to review in any detail the many experimental investigations which 

 have been undertaken in this connection. A few of the most recent 

 and important results are given in the accompanying table from Halli- 

 burton 's Physiology: 



