CIRCULATION 29 



organ. The latter lias been determined by experiments 

 which prove that in every minute each hundred grams 

 of the leg receive 5 c.c. of blood ; while the same weight 

 of spleen would receive 58 c.c., of brain 136 c.c. and of 

 the thyroid no less than 560 c.c. in the same time. 



Circulation Velocity. Circulation velocity does not 

 refer to the rapidity of flow through any given vessel, 

 but to the time it takes for a given portion of blood to 

 pass between two points as from one jugular vein 

 through the heart, pulmonary artery, veins, left heart, 

 aorta and capillaries of the head to the opposite jugular. 

 This is determined by putting some methyleiie blue in 

 one jugular and watching for its appearance in the 

 other. This has been accurately determined in many 

 lower animals and is estimated to be about thirty-two 

 seconds in man. As the rate of flow is much more rapid 

 in the largest than in the smallest arteries, in the arteries 

 than in the capillaries, and in the veins than in the capil- 

 laries, it can not be calculated by simply watching the 

 speed with which corpuscles pass through one of the 

 vessels. Of course the velocity of the blood current will 

 not be confounded with the rate of the pulse, which is 

 an impact rather than a current. 



The Pulse. The pulse is seen and normally felt only 

 in the arteries. The capillary and venous systems are so 

 much wider than the arterial, that the force of the heart- 

 beat is not displayed in the pulsatile or expansile man- 

 ner so characteristic of the latter. The column of blood 

 extending from the heart throughout the arteries may 

 be compared to a series of balls suspended by strings 

 and each touching the other. If the first of the series 

 is struck sharply the power will be transmitted through- 

 out the series, but it will visibly affect the last only. If 

 fresh blood is pumped into the aorta, that particular 



