336 



ANIMAL NATURE AS A WHOLE. 



[III. 



658. As this period of perfection of all the functions is 

 attained sooner in some animals than in others, and continues 

 for a shorter period, it determines the duration of life in 

 different classes of animals ; and in this there is the greatest 

 difference, the period in which the sexual organs are active, 

 varying from a day to a hundred years. The interval between 

 the cessation of sexual activity and death, seems only to be an 

 addition to life, — a something given over and above ; and we 

 will term it the period of decline. But before entering on the 

 consideration of this period, we must consider the whole plan 

 of perfect animal life, the proper knowledge of which is the 

 great object of this system of physiology. 



