VASCULAR SYSTEM. Ill 



/?. By means of the internal or lining membrane; the 

 fibrous membrane of the aorta does not unite directly with 

 the fleshy substance of the heart. 



Q. How are the semilunar valves formed? 



*#. By the folds of the lining membrane, and the cor- 

 responding festoons of the fibrous membrane of the aorta. 



Q. What advantage results from the undivided trunk of 

 the aorta descendens? 



t/2. The impulsive power of the heart is better preserv- 

 ed over the great length of the branches of the inferior 

 aorta. 



Q. What is the most accurate estimate of the number 

 of branches and subdivisions of each artery? 



#. That made by Haller, amounting to twenty. 



Q. In ramifications from the main trunk of an artery, 

 what favours the current of blood in the branch ? 



#. A projection formed by the folds of the internal 

 membrane of the artery, corresponding with the angle 

 coming from without, breaks the column of the blood and 

 favours the change of its current. 



Q. Does the tortuous course of the arteries diminish the 

 impetus of the blood? 



*#. From experiments. made on animals, it was ascer- 

 tained that the tortuous course of the arteries does not di- 

 minish it. 



Q. Are anastomoses formed near to the heart, or remote 

 from it? 



/?. They are found distant from the heart, and they are 

 more numerous in those organs whose motions are not con- 

 trolled in any way by other parts. You see this exempli- 

 fied in the arteries of the brain. 



Q. You see the large arteries deep-seated and well pro- 



