238 HUMAN PHYSIOLOGY CHAP, xvi 



is grouped into nerve centers, which control many of the higher 

 vital functions, as breathing, heart beat, swallowing, secretion, 

 etc. 



10. The pons, or bridge, is a mass of nerve fibers connect- 

 ing the bulb, cerebellum, and cerebrum. 



1 1. The cerebellum, or little brain, is the organ which makes 

 the muscles used in sitting, standing, walking, and balancing 

 work together in the right order, and gives us our bearings in 

 space. 



12. The cerebrum is the largest part of the brain, forming 

 about four fifths of the entire mass. It consists of two hemi- 

 spheres, each having four main lobes, known as the frontal, 

 parietal, temporal, and occipital. 



13. There are numerous nerve centers in the cerebrum, 

 each having its special function to perform. The three im- 

 portant areas are known as the sensory, the motor, and the 

 association. 



14. The sensory areas receive impressions from the sensory 

 nerves coming from all parts of the body. The motor areas 

 send out messages over the motor nerves to the muscles and 

 glands. The association areas connect the sensory and the 

 motor areas of the brain, and may serve as the centers for 

 thought. 



15. The ganglia and nerves of the sympathetic system supply 

 all the organs of the chest and abdomen. These organs are 

 also supplied with spinal and cranial nerves, so that they have a 

 double nerve supply. 



1 6. The brain and the mind stand in close relation to each 

 other. If we wish a strong, active, vigorous mind, we must see 

 that the brain is kept in an excellent physical condition. 



