Epidemics. 239 



comprehensive question, but surely it deserves a passing 

 consideration. Suppose it be assumed that 22 parts of 

 blood represent the given quantity of blood flowing through 

 the system, and to the arteries be allotted 6 parts, to the 

 veins 7 parts, and to the capillaries 9 parts, which together 

 will make 22 parts ? (The quantities here given are purely 

 hypothetical.) 



The capillary system is here represented as containing 

 more than either the venous or arterial systems ; that it of 

 course delivers its blood to the veins at a slower rate of 

 velocity than that belonging to the arteries ; but the veins, 

 having a larger capacity for blood than the arteries, the 

 discrepancy of velocity in the veins is compensated by their 

 greater cubic contents, giving to the right side of the heart 

 an amount equal to that injected into the arterial system 

 by the left side of the heart. But the most difficult system to 

 understand is the capillary system, a system which appears to 

 have some motor power plus that of the heart, and, in a 

 measure, independent of it ; nevertheless, as a whole, it acts 

 synchronously with the blood propulsion delivered to it by 

 the action of the heart. Moreover, the momentum with 

 which it receives blood from the heart invariably regulates 

 the momentum of the circulation running through its own 

 finely spread net-work of tubing; but, inasmuch as the 

 blood travels through a larger cubic space in the capillaries 

 than in the arteries, as well as its being checked by increased 

 friction, the momentum offeree with which it enters the veins 

 must be considerably diminished. But put the matter in 

 another light, and then a clearer aspect will be obtained. Let 

 the time or velocity be the same, and the size of the bodies 

 the same, in which two hearts are placed. One heart shall use 

 force in one hour equal to move loolbs., and the other force in 

 the same time equal to move 8olbs., the weight being divided 



