SPECIAL PHYSIOLOGY. 



GENERAL CONSIDERATION AND CLASSIFICATION 

 OF THE FUNCTIONS. 



In every living structure of a complex nature, we see a great va- 

 riety of actions resulting from the exercise of the different properties 

 of its several component parts. A general survey of these, with 

 reference to their mutual rela-tions to each other, will show that they 

 may be associated into groups, each consisting of a set of actions, 

 which, though different in themselves, concur in effecting some posi- 

 tive and determined purpose. These groups and actions are termed 

 functions. A function may be defined the action of an organ or 

 syste7n of organs. Thus respiration is a function ; its object is the 

 conversion of venous into arterial blood, and its instrument is the 

 lungs. 



On further examination of these functions, we find that they are 

 susceptible of some degree of classification. There is a set which 

 is found to be possessed by all living organized beings, vegetable as 

 well as animal ; these are called the organic or vegetative. These 

 may be again subdivided into those concerned in the maintenance of 

 the structure of the individual, or the nutritive, and those to which 

 the preservation of the species is due, or the reproductive. There 

 is then a set which is possessed by animals alone, in addition to 

 those belonging to vegetables, these are called the animal functions^ 

 or the functions of relation, and are dependent for their exercise 

 upon the existence of a nervous system, the presence of ivhich latter 

 in an organized being marks the distinction between an animal 

 and a vegetable. The animal functions render the individual con- 

 scious of external impressions, and capable of executing spontaneous 

 movements. 



These two sets of functions, the organic and animal, are mutually 

 dependent on each other, the organic supplying the material neces- 

 sary for the repair of the instruments of the animal ; whilst the 

 animal functions, in which are included sensation and voluntary 

 motion, are essential to enable the individual to obtain that material 

 which the plant, from the different provision made for its support, 

 can obtain without any such assistance. In the animal body, all 

 the functions are so completely bound up together, that none can be 

 suspended without the cessation of the rest. 



