222 GENERAL ANATOMY OF THE SANGUIFEROUS SYSTEM. 



blood must flow faster through the branches than through the 

 primitive trunk, as the same quantity of blood must be disposed 

 of in the same space of time ; and that by this means, friction 

 is reduced, as there is less surface of the vessels exposed to the 

 passing of the blood, and the force of the heart's action is 

 continued much farther through the system. 

 This manifest discrepancy among anatomists of high reputa- 

 tion, is explicable by the facts made known from careful mea- 

 surement by M. Bizot ; viz. that all the different modes of form 

 above specified, are met with in the arterial system, and that 

 each artery, so to speak, has its peculiar and constant form 

 in a healthy state ; the corresponding arteries of the two 

 sides of the body, being analogous in shape. To establish the 

 truth in regard to these points, this writer measured 2,162 

 arteries, in addition to the measurements of the aorta already 

 given.* All the modes of formation of the arteries he reduces 

 to the five following. 



1. A cone, the base of which is directed towards the heart, 

 met with 39 times in the 100. 



2. Two truncated cones opposed by their truncated summit, 

 met with 28 times in the 100. 



3. A cone with its summit directed, towards the heart, met 

 with 14 times in the 100. 



4. A perfect cylinder, met with 12 times in the 100. 



5. Two truncated cones opposed by their base, met with five 

 times in the 100. 



It is seen by this statement that, contrary to the opinion of 

 most anatomists, the perfect cylinder is one of the rarest forms. 

 The arteria innominata belongs to the second class, or in 

 other words, forms a tube narrowed in its middle, in nearly 

 one half of the cases in which it was examined. The primitive 

 carotid belonged to the same, in more than three-fourths ; whilst 

 the same arteries but twice in one hundred and thirty-six in- 

 stances presented the form of a cylinder. 

 The brachial, primitive and external iliacs, were found to 



* It has been computed that the blood flows 5 ; 233 times slower in the 

 capillaries than in the aorta. p. 



