6 J'HYSIOLOGY. 



individual, the community, the state, and the nation. The 

 cell is an individual, the community is a tissue, the state is 

 an organ, and the nation is one body. 



Let us proceed to study the nature of the individual cell, 

 and the combined actions of these individuals in that com- 

 munity called the human body. 



Summary. i. Health is essential to comfort and efficiency in 

 work. 



2. Our artificial mode of life is at variance with nature's laws. 



3. Only by obeying the laws of nature can we preserve health. 



4. We should learn these laws of nature from the advice and ex- 

 perience of others, and not by the expensive process of suffering from 

 disobedience. 



5. Anatomy is the science of structure. Human anatomy is the 

 science of the structure of the human body. 



6. Physiology is the science of function. 



7. Hygiene is the art of preserving health. 



8. Cells are the units of structure in the body. 



9. A tissue is a group of similar cells having a single function. 



10. An organ is a part having a special work or function. The 

 organs work together for the common good of the whole organism. 

 This working together results in 



1 1 . The physiological division of labor, in which each organ works 

 for all the others, and is dependent on all the other organs. 



Questions. i. What are some of the ways in which we most fre- 

 quently violate the laws of health ? 



2. Name the more important organs of the body and their functions. 



3. Name the different tissues of one of these organs. 



