60 



THE RESTING AND DIVIDING CELL 



of processes are essential to the work of the cell and depend upon 

 each other. The anabolic activities are concerned chiefly with 

 nutrition and the katabolic, with energy release. For example, 

 in order to perform the anabolic functions of assimilation, the 

 cell is dependent on the energy derived from the katabolic func- 

 tion of respiration. 



Ingestion 



Digestion 



Absorption 



Circulation 



Assimilation 



Nutrition 



Growth 



Secretion 



Reproduction 



Respiration 

 Irritability 

 Excretion 

 Motion 



Anabolism ^ 



Katabolism 



Metabolism 



Cell division. When a cell is not at rest, it is in a state of divi- 

 sion. There are two methods of division: 1. Direct division 

 also called amitosis (a without; mitos thread), and 2. in- 

 direct division or mitosis. In amitosis, direct division, the nu- 

 cleus simply pinches in half and becomes separated into two 

 daughter nuclei. The cytoplasm sometimes cleaves and a part 

 goes with each nucleus. This sort of division takes place only in 

 cells which are very active and need very many nuclei in the work 

 they are doing. Amitosis may also occur when cells have been 

 very active, and the nucleus, becoming exhausted, multiplies 

 rapidly by breaking into fragments. 



Mitosis or indirect cell division. Mitosis is a very compli- 

 cated process when compared with amitosis. The nucleus lives a 

 very long time in an active and young cell, and will divide a great 

 many times. Each time the nucleus divides, the entire cell di- 

 vides, forming two new cells. Each cell will have exactly the 



