254 STUDIES IN PHYSIOLOGY 



Or let us take a more complex example of cooperation 

 between the different organs. Suppose I am a batsman on 

 the baseball field, and a ball, thrown by the pitcher, is 

 coming swiftly toward me. For an instant I wait with 

 every muscle rigid ; then my arms swing the bat to strike 

 vigorously at the passing ball. If I am fortunate enough 

 to make a hit, my hands at once drop the bat, and my legs 

 begin to carry me swiftly toward first base. On reaching 

 this goal, if I stopped to consider the physiological condi- 

 tion of my body, I should find that my heart was pumping 

 twenty to fifty times more per minute than it was when I 

 started ; that my rate of breathing was more rapid ; and that 

 the flow of perspiration had been considerably increased. 

 I should doubtless experience a feeling of satisfaction that 

 I had not been " struck out " by the pitcher, and a determi- 

 nation to complete the run of the bases and thus make a 

 score for my team. 



Functions of the Nervous System. All the succession of 

 activities just described would be utterly impossible if some 

 means were not provided for making the organs work 

 together for the common good. The arms could not see 

 to strike at the ball ; the legs could not make themselves 

 run toward first base ; nor could the heart, lungs, and skin 

 respond to the sudden exertion of the rest of the body. It 

 is the nervous system that controls the action of each of the 

 organs in our body and brings about a cooperation between 

 them. All our sensations, too, and our will power are doubt- 

 less correlated with the activities of the nervous system. 



Parts of the Nervous System. The nervous system may 

 be said to consist of nerve centers and nerve trunks. The 

 principal nerve centers are in the brain and spinal cord. 

 These are sometimes said to constitute the central nervous 

 system or cer'e-bro-spi'nal center (Latin cerebrum = brain). 

 We have already seen that these delicate organs are inclosed 

 and wonderfully protected by the bony cranium and spinal 

 column. 



