HOW DO WE CONTROL THE HUMAN MACHINE? 387 



pineal gland 

 pituitary* 



parathyroid 

 -thyroid 



tWmus 



liver 



of the body go on without our knowing much about what 

 is taking place. 



Two Kinds of Control. Your unconscious body con- 

 trol is of two sources. One is under the care of the so- 

 called autonomic nervous 

 system ; but there is another 

 control brought about by 

 some very wonderful glands 

 in the body. These glands 

 are not connected with the 

 food tube or other parts of 

 the body, but instead pour 

 their secretions directly into 

 the blood. They are called 

 endocrine glands. You have 

 heard about some of them. 

 The thyroid gland, for ex- 

 ample, sends certain messages 

 into the blood which causes 

 a greater or lesser activity 

 on the part of the body. 

 The suprarenal glands are 

 used at times when we are 

 angry, or when we wish to 

 make a desperate muscular effort of some sort. The 

 pituitary gland, a little organ no larger than a chestnut, 

 found at the base of the brain, controls the size of the 

 human body. There are several of these glands which 

 you will learn more about later in your study of biology, 

 but they have a very definite effect on the running of the 

 human machine. If they are in good condition, the 

 human machine behaves normally. If they are out of 

 condition, the machine may behave very badly. 



Other Things that Influence Body Control. You have 

 all found that you could not work as well when you were 



creas 



spleen 

 adrenal 

 sex gland 



Glands that influence body control. 



Can you tell what each one shown 



does for the body ? 



