154 Life and Health 



to pour out gastric juice, the arteries that supply these 

 organs are dilated, and so the parts are flushed with an 

 extra supply of blood, and thus are aroused to greater 

 activity. 



Again, the ordinary supply of blood to a part may be 

 lessened, so that the organ is reduced to a state of inac- 

 tivity, as occurs in the case of the brain during sleep. We 

 have in the act of blushing a familiar example of sudden 



FIG. 80. The Right Axillary 

 and Brachial Arteries, 



with Some of their 

 - Main Branches. 



enlargement of the smaller arteries of the face and neck, 

 called forth by some emotion which acts on the vaso-motor 

 center and diminishes its activity. 



Experiment 65. Hold up the ear of a white rabbit against the light 

 while the animal is kept quiet and not alarmed. The red central artery 

 can be seen coursing along the translucent organ, giving off branches 

 which by subdivision become too small to be separately visible, and 

 the whole ear has a pink color and is warm from the abundant blood 

 flowing through it. Attentive observation will show also that the 

 caliber of the main artery is not constant; at somewhat irregular 

 periods of a minute or more it dilates and contracts a little. 



234. The Pulse. When the finger is placed on any part 

 of the body where an artery is located near the surface, as, 



