THE CIRCULATION OF THE BLOOD AND LYMPH 125 



The total circulation -time is properly the time required for the 

 whole of the blood to complete the round of the pulmonary and 

 systemic circulation. But there are many routes open to any given 

 particle of blood in making its systemic circuit. If it passes from 

 the aorta through the coronary circulation it takes an exceedingly 

 short route. If it passes through the intestines and liver, or through 

 the kidney, or through the lower limbs, it takes a long route. So 

 that to determine the total circulation-time by direct measurement 



FIG. 43. MEASUREMENT OF THE PULMONARY CIRCULATION-TIME IN 

 RABBIT BY INJECTION OF METHYLENE BLUE. 



we must know (i) the quantity of blood that passes on the average 

 by each paih in a given time, and (2) the average circulation-time of 

 each path. If the average weight of blood in each organ be repre- 

 sented by w v ' 2 , w# etc. ; and the average circulation - times 

 by *i *& *& etc. ; and / be the total systemic circulation-time ; then 



w \7> W f7t W 37> etc -> will represent the quantity of blood passing 



r i f -2 '8 



through each organ in / seconds, since in the average circulation- 



