GENERAL ANIMAL FUNCTIONS. 95 



Function. System. 



(a) Metabolism Nutritive (digestive, respiratory, 



circulatory, excretory) . 



(b) Support and protection Skeletal and integumentary. 



(c) Growth (No special organs). 



(d) Reproduction Reproductive. 



(e) Motion and locomotion Muscular, in connection with skele- 



tal. 



(f) Sensation Nervous. 



5. Metabolism includes both building-up processes and 

 tearing-down processes. The former add to the materials 

 of the body and include digestion and assimilation. The 

 latter include the oxidation that takes place in the cells, 

 the display of motion or heat that comes from it, and the 

 excretion of the waste materials. 



6. The hard or skeletal parts are secreted by certain 

 cells. This material may be external or internal. It is 

 important in determining the arrangement and action 

 of the soft and more active parts of the animal. 



7. Growth and reproduction are the outcome of the 

 nutritive work. Growth means the building up of the 

 individual; reproduction means the forming of a new 

 individual at the expense of the old. Whether in the 

 one-celled animals or the higher ones, reproduction is 

 always a division of the parent. If only one parent is 

 necessary, we speak of reproduction as non-sexual. If 

 cells from two parents are necessary, it is called sexual. 



8. The nervous and muscular systems are closely bound 

 together, both in structure and function. All muscles 

 have nerves running to them. Sensation alone, without 

 power to respond would be of no value to an animal. In 

 a similar way, power to act without the ability to get im- 

 pressions of the internal and external conditions would 

 be meaningless. The action would be unguided. 



