MENTAL DIFFERENCE AND DISORDER. 195 



appear in middle life, lose much or all of their violence, and 

 perhaps dangerousness, in age. 



This, and certain other mental characteristics of age 

 among the lower animals, such as sedateness or demureness, 

 are advantageous both to the animals themselves, to their 

 fellows, and to man. But there are other equally common 

 and prominent features in character or disposition, begotten 

 by approaching senility, of which the same cannot be 

 said, for instance, moroseness, suspiciousness, irritability or 

 irascibility, savageness or ferocity, sullenness, sulkiness or 

 surliness, vindictiveness, distrustfulness, impatience, caprice, 

 ill-temper, touchiness or testiness of temper, readiness to 

 take offence, unsociality, apathy or lethargy, dulness or 

 stupidity, treacherousness, sourness of temper, discontent. 

 In some cases these evil qualities are only too probably the 

 fruits of man's ill-usage, including captivity, perhaps during 

 a series of years ; while in others they may be the result of 

 harsh treatment at the hands of younger competitors of 

 their own kind, in that ' struggle for life ' which is no less 

 keen among other animals than among mankind, civilised or 

 savage. 



The moose is suspicious in proportion to its age, this 

 suspiciousness tending or leading gradually to morbid imagi- 

 nation and delusion (Gillmore). 



The frequently marked contrast in character or disposition 

 in the same individual in youth and age is matter of as 

 daily observation in other animals as in man. Thus Baird 

 and other authors point out that the Barbary ape, the capped 

 ape, the chimpanzee, and various baboons, which in youth 

 are docile, gentle, affectionate to man, mild, placid, playful, 

 good-tempered, lively, intelligent, in age become ill-tempered, 

 fierce or ferocious, mischievous, sullen, morose,- intractable, 

 incorrigible, unteachable, untamable, obstinate, not amen- 

 able to punishment, dull, troublesome. 



Such character-contrasts are as frequent in the dog as 

 in various species and genera of monkeys. The dignified 

 silence and repose of dogs when they grow in years contrast 

 remarkably with the noisy, restless vivacity of their youth. 

 The manners of the parrot and other pet animals, which in 



o 2 



