132 VASCULAR SYSTEM. 



side of the heart, in consequence of pulmonary obstruction, 

 or of an irregular action of the heart. These occasion a 

 psuedo-pulsation, resulting from the contractility of tex- 

 ture, not from irritability. 



Q. How far is this reflux operative? 



ft. Rarely beyond the great trunks; it is stopped by 

 the valves. Haller said it extends to the iliacs. 



Q. Why do wounded veins inflame and unite so much 

 more speedily than arteries? 



ft. Because the tonic vital forces are greater in the veins 

 than arteries, because the action of the arteries may pre- 

 vent union, and perhaps because there is more cellular tex- 

 ture in the veins than in the arteries. 



Q. How is the blood moved from the general capilla- 

 ries through the veins? 



ft. By the insensible contractility of the capillaries; by 

 an absorbing power which commences in the venous ra- 

 mifications, and extends towards the venous trunks. 



Q. But as the resistance to the motion of the blood in 

 the veins is often greater than the impulse, how does it 

 get forward? 



ft. By various aids; by anastomoses; by muscular ac- 

 tion and pressure ; by assistance from the pulsation of the 

 neighbouring arteries; by the motion of certain parts, as 

 the elevation and depression of the cerebral mass; by the 

 locomotion of other organs, as the gastric ; and by external 

 frictions and motions.* 



Q. Can you give a parallel view of the circulation in 

 the arteries and veins? 



* For a more particular account of the forces, by which the blood 

 is made to circulate in the veins, see Arnott's Elements of Physics, 

 American Edition, p. 446, et seq. 



