VASCULAR SYSTEM. 133 



In the arteries there is 



Pulsation, 



Rapid flow of blood, 



Small capacity and 

 thick parietes, 



No necessity for ac- 

 cessory aid, 



Blood flowing per 

 saltern, 



Very little arterial 

 gravitation. 



In the veins there is 

 No pulsation, 

 Slow motion of the blood, 

 Great capacity and thin 



parietes, 

 Necessity for accessory 



aid, 

 Uniform flow of blood, 



Power of gravity in the 

 veins. 



Q. What are the effects from an organ of impulse at the 

 origin of the arteries? 



t#. It gives uniformity of pulsation or motion in the 

 arteries, and you find all the arteries of the body equally 

 dilated or contracted after death. 



Q. Now, what results proceed from the absence of an 

 organ of impulse at the capillary origin of the veins ? 



t/tf. The blood is propelled with very various power in 

 different parts of th6 body ; and there is great variety in 

 the states of fulness or contractions of different veins in the 

 several parts of the body. 



Development of the Arterial System with Black Blood. 



Q. Is the arterial or venous system most developed in 

 foetal life? 



w2. The arterial much more so; less blood returns by 

 the veins, because of the quantity exhausted by nutri- 

 tion. 



Q. What' veins have been found developed before the 

 arteries? 



#. The umbilico mesenteric in the chick. 



