196 PHYSICAL CAUSES OF 



youth are marked by sprightliness, in age are characterised 

 by sedateness or demureness. Sedateness and love of solita- 

 riness appear with age in the hare, in place of the friskines^ 

 and love of society that marked its youth. 



The mental characteristics of youth in other animals, as 

 in man, include the following good and bad qualities 



1. Good: spirit, energy, activity, agility, ardour or en- 

 thusiasm, intelligence, vivacity or sprightliness, playfulness 

 or love of sport or games, animation or liveliness, love of fun 

 and of society, confidence in themselves and man, versatility, 

 flexibility or plasticity of mind, eagerness. 



2. Bad : forwardness or impudence, mischievousness and 

 love of mischief including destructiveness, inconsiderate- 

 ness, haste, rashness or precipitancy, headstrongness, im- 

 pulsiveness, inexperience, excessive feeling or a tendency 

 thereto, thoughtlessness. 



There is a most interesting and intimate connection or 

 relationship between mental change and the development of 

 physical disease, as well as between both and morbid con- 

 ditions of the brain or nerve- substance, observable in the dog 

 or other animals, as in man. This has been brought out 

 of late years by the experimental investigations of various 

 physiologists and pathologists, British and foreign. Thus 

 Dr. Major, of Wakefield, gives a case of the association of 

 irritability of temper, with loss of memory and diminished 

 intelligence, including failure to recognise her master, coin- 

 cidently with the development of fits, apparently of an 

 epileptic character, and with partial paralysis of the limbs, 

 all in an old terrier bitch, these conditions, moreover, being 

 coincident with senile atrophy or degeneration of the brain. 

 He gives a plate of the morbid appearances in the brain, 

 and remarks : ' In the dog, in old age, decided pathological 

 changes occur in the nerve elements of the brain,' and, 

 comparing these with similar changes in man, he goes on: 

 6 It cannot escape observation that the resemblance between 

 them is very great .... In both we find a progressive 

 granular degeneration and atrophy of the cells .... and 

 the same destruction of nerve branches, while in the 

 neuroglia we have evidence of a similar morbid process.' 



