PROBLEM 169 



191 



partially protected by the ribs, is a cavity, the body cavity, divided 

 into two unequal parts by a wall of muscles, the diaphragm. The 

 body cavity contains the working parts of the 

 machine : a. The organs of digestion, gullet, 

 stomach, small intestine, large intestine, the liver 

 and pancreas (two digestive glands), and the 

 spleen (a gland connected to the digestive 

 organs), b. The organs of respiration, the 

 lungs and tubes which connect them with the 

 outside of the body. c. The organs of circu- 

 lation, the heart and blood vessels, d. The 

 organs of excretion, the kidneys, e. Most im- 

 portant of all is the nervous system. This con- 

 sists of the brain and spinal cord with the nerves 

 growing out from them, and several different 

 sense organs, which are at the. outside of the 

 body and send nerves inward to connect with 

 the central nervous system. 



Your instructor will demonstrate these to 

 you. We will spend most of the remainder 

 of our course in learning more about the use 

 of these various organs in the human machine. 



Conclusion. 1. What are the chief organs 

 of the human body cavity ? 



2. Which of these are in the body cavity and 

 which extend into other parts of the body ? 



3. Which are chiefly outside the body cavity 

 but send branches in? (Get help from your 

 instructor or your textbook, page 271, Civic 

 Biology.) 



4. Why are sense organs in the skin ? How do they send mes- 

 sages to other parts of the body ? 



PROBLEM QUESTIONS 



1. What is the unit of structure in the human body? 



2. Why do the cells in different parts of the body differ in shape 

 and size? 



THE ORGANS WITHIN 

 THE HUMAN BODY. 

 READ FROM ABOVE 

 DOWN : 



t, tongue ; L, larynx ; 

 CB, gullet ; I, lung ; 

 H, heart ; st, ster- 

 num ; s.c, spinal 

 cord ; d, diaphragm ; 

 L, liver ; S, stom- 

 ach ; A;, kidney ; p, 

 pancreas ; i, small 

 intestine ; /, large 

 intestine ; a, vermi- 

 form appendix; B, 

 bladder ; R, rectum. 



