114 VASCULAR SYSTEM. 



*ft. To ossification, which occurs most frequently about 

 the aorta and mitral valves. 



Q. What renders the pulse so intermitting in old age? 



tfl. It is probably owing to this ossification of the lining 

 membrane. 



Q. Does this ossification of the lining membrane equally 

 endanger the old man and the rniddle-aged ? 



#. That ossification which is not alarming in the old, 

 is exceedingly dangerous to the adult. 



Q. What cellular investments have the arteries ? 



*fl. There is a loose cellular envelope which connects 

 them with surrounding parts, and a dense cellular coat. 



Q. Does cellular substance enter into the organization 

 of the fibrous coat? 



/?. It does not; hence the brittleness of that coat, and 

 its disposition to rupture in aneurism. 



Q. Why are not absorbents found in the arteries? 



A. Because in the peculiar and common or lining mem- 

 brane of these vessels there is no cellular texture. 



Properties of the Vascular System with Red Blood. 

 1. Physical Properties. 



Q. What physical property do the arteries possess in 

 an eminent degree? 



t/#. Elasticity, and this property distinguishes them prin- 

 cipally from the veins. 



Q. What tubes in the body are kept open by this elas- 

 ticity ? 



#. The arteries, the trachea, the meatus auditorius of 



