CHAPTER VIII 



PHYSIOLOGY 



The maintenance of any living body requires the cooperation of 

 several functions which will attain similar fundamental results 

 wherever they occur in living material. The principal functions 

 performed by the structures in the animal body are: (1) support 

 and protection, (2) movement and locomotion, (3) digestion, (4) 

 respiration, (5) circulation, (6) excretion, (7) reproduction, (8) 

 reception and conduction of stimuli, and (9) internal regulation. 

 These functions merge into one living process which involves the 

 building up of protoplasm, transformation of energy, and repro- 

 duction. During the execution of these activities energy is con- 

 stantly being changed from the potential to the kinetic form. 



The collective term metabolism is employed when referring to all 

 of the interactions involved in the living process of protoplasm. It 

 includes the processes concerned with conversion of food into proto- 

 plasm, release of energy through oxidation, production of heat, 

 movement, elimination of wastes, or in other words these processes 

 are chiefly : ingestion, digestion, egestion, absorption, transportation, 

 assiyyiilation, respiration, oxidation, and elimination. The processes 

 concerned with the conversion of food material into protoplasm (build- 

 ing up) constitute the phase of metabolism known as anabolism. In- 

 cluded here are ingestion, digestion, absorption, transportation, and 

 assimilation. The oxidation of materials of the protoplasm to liberate 

 energy, and the elimination of wastes incidental to it, is known as 

 catabolism or the ''breaking down" phase. 



Metabolism is one of the fundamental features of all protoplasm ; 

 therefore all physiology, since it is a study of the functions of living 

 organisms, must be concerned with metabolism. It includes all of 

 the chemical changes and transformations by which energy is sup- 

 plied for the activities of the protoplasm. For convenience, the 

 several functions will be discussed separately with the thought of 

 bringing out their expression in different types of animal life. 



Support and Protection 



In Protozoa there is no very elaborate adaptation in this direc- 

 tion. The presence of a cuticle in some and the secretion of a hard 



16C 



