IQO APPLIED PHYSIOLOGY 



If a part is continuously supplied with an excess of 

 blood by dilated arteries, there is apt to be an overgrowth 

 of some of its tissues, especially of connective tissue. An 

 excess of this tissue interferes with the action of the work- 

 ing cells of the part. This change is apt to occur especially 

 in the arteries themselves, making them thick and hard. 

 It naturally comes on during old age, but is often hastened 

 by the use of strong drink. The affected arteries cannot 

 change their size, and so the parts which they supply 

 surfer in nutrition. Although an excess of blood may go 

 to a part, yet it is not renewed so often as it should be. 



SUMMARY 



1. The muscles in the arteries give them the power of 



becoming smaller or larger in order to regulate the 

 amount of blood going to any part of the body. 



2. The contraction and relaxation of the arteries is con- 



trolled by a set of nerves called vaso-motor nerves. 



3. Heat, cold, work, and mental influences are a few causes 



which excite the action of the arterial muscles. 



4. Contraction of arteries near the surface and dilatation 



of the deeper ones is the common cause of taking 

 cold. 



5. Alcohol causes a paralysis of the muscles of the arteries 



so that they may remain permanently enlarged. The 

 arteries of the face and stomach are most affected. 



6. Small blood tubes, when cut, bleed for a moment until 



the ends of the tubes contract and a clot plugs them 

 up completely. 



7. Large blood tubes may bleed until death occurs. 



Bleeding can always be stopped by grasping the 

 part boldly and firmly. 



