194 PHYSICAL CAUSES OF 



senses and of sensation; the same tendency to blindness, 

 deafness, muscular decrepitude and stiffness of the joints ; 

 the same indisposition to fatigue, bodily or mental ; the 

 same indifference to former pursuits and pleasures. 



The decay of the mental powers the mental degenera- 

 tion or weakness of senility is observable, for instance, in 

 the old, worn-out horse or dog the racer or harrier. This 

 mental degeneration involves the moral powers where they 

 have been developed to any appreciable extent. Thus in 

 certain old formerly well-behaved dogs there is, as in man, 

 a weakening of the moral sense a yielding to, or non-resist- 

 ance of, temptation, an indecision of character equally 

 attributable to gradual loss of will. 



Not only, however, are the mental infirmities of age in 

 other animals perceptible to man, where he is at all ob- 

 servant ; they are felt also by the animals themselves. The 

 sense of decadence of physical strength in the horse and dog 

 leads to the cessation of the races or sports in which they 

 used to be engaged. They leave active and fatiguing 

 pursuits to the young, who are possessed of ardour as well 

 as vigour. They prefer to watch and wait rather than pur- 

 sue, recognising at once the necessity and advantage of 

 ' taking things easy.' The old harrier substitutes cunning 

 for speed. 



Age, however, is necessary to the development of the 

 mental powers equally in young animals and in the human 

 infant, though its rapidity and extent vary in different 

 species and genera. The acquisition of such qualities as 

 caution, cunning, wariness, which are obviously the result 

 of painful experience, is gradual, and it is one of the many 

 characteristics of age. The power, or at least the practice, 

 of reflection is developed, as in man, in proportion to age. 

 Attachment to the person of man, or to place, is also a 

 growth of or with age. There is an absence of any such 

 feeling, for instance, in the pup. 



On the other hand, in age there is frequently a weaken- 

 ing or loss of the dislikes or furiosity that characterised 

 earlier periods of life perhaps the greater part of its course 

 while the violent forms of insanity such as mania, which 



