ANIMAL FUNCTIONS. 97 



nature never furnishes any organs but such as are abso- 

 lutely necessary, so the terminations of the wings of 

 Birds, instead of being furnished with bones and muscles 

 which have the prehensile power, like the hand, are only 

 provided with such as are fitted for the insertion of 

 quills. 



PART III. 



ANIMAL FUNCTIONS. 



THE Vital functions, or actions, of animals are such as 

 are immediately essential to life, as the circulation of the 

 blood, respiration, secretion, and absorption. Without 

 these the animal cannot exist. The animal functions are 

 those which support and renovate the system, and with- 

 out which the vital functions could not long be maintain- 

 ed, as digestion, nutrition, and the formation of chyle. 

 These are not immediately essential to life, but may be 

 suspended for a time. The mechanical functions are 

 such as depend on the will, as the action of the muscles, 

 whether employed for the purposes of swimming, flying, 

 or walking. The instruments by which mechanical 

 action is effected have been the chief subjects of the 



What are the vital functions of animals 7 What are the animal func- 

 tions ? What are the mechanical functions ? 



