22 THE VITAL PROCESSES 



1. That of maintaining in the body a nutrient fluid for 



the cells. 



2. That of bringing the body into such relations with its 

 surroundings as will enable it to secure materials for the 

 nutrient fluid and satisfy its other needs. 



The first problem is internal and includes the so-called 

 vital processes, known as digestion, circulation, respiration, 

 and excretion. The second problem is external, as it were, 

 and includes the work of the external organs the organs 

 of motion and of locomotion and the organs of special 

 sense. These problems are closely related, since they are 

 the two divisions of the one problem of maintaining life. 

 Neither can be considered independently of the other. In 

 the chapter following is taken up the first of these problems. 



Summary. The individual parts, or units, that form the 

 body organization are known as cells. These consist of 

 minute but definitely arranged portions of protoplasm and 

 are held together by the intercellular material. They build 

 up the body and carry on its different activities. The 

 tissues are groups of like cells. By certain general activ- 

 ities the cells maintain their existence in the tissues and by 

 the exercise of certain special activities they adapt the 

 tissues to their purposes in the body. The body, as a cell 

 organization, has its activities directed under normal con- 

 ditions toward a single purpose that of maintaining life. 

 In the accomplishment of this purpose a nutrient fluid is 

 provided for the cells and proper relations between the 

 body and its surroundings are established. 



Exercises. i. If a tissue be compared to a brick wall, to what do 

 the separate bricks correspond ? To what the mortar between the bricks ? 



2. Draw an outline of a typical cell, locating and naming the main 

 divisions. 



3. How do the cells enable the body to grow ? Describe the process 

 of cell-division. 



