36 EXPEKI MENTAL STUDY. 



to be done on the other. Spalding, for instance, points out 

 the desirability of further experiment and observation on 

 what he calls ' inherited acquisition ' a doctrine capable of 

 experimental proof or demonstration. Houzeau, again, has 

 suggested, as an important subject for future research in- 

 cluding both experiment and observation the taming and 

 studying, in their native countries, of the great anthropoid 

 apes particularly the soko, which is as yet known only to 

 Livingstone and other forms of the gorilla and chimpanzee. 

 Among other legitimate and desirable, and at the same time 

 harmless, subjects of experimental investigation by man is 

 the effect of mirrors, pictures, and patterns on various 

 animals. 



Many experiments are performed for man by nature, by 

 disease or injury in himself or other animals; but their 

 value or importance is seldom evident, unless to the accom- 

 plished or experienced physiologist, pathologist, or naturalist. 

 In the hands of such men, however, these experiments of 

 nature's may be reproduced artificially by imitation; so 

 that the lessons they are calculated to teach may be duly 

 learned and applied. In other words> the results of human 

 experiment may be made, when necessary or desirable, to 

 imitate those of disease or injury ; or the diseases or injuries 

 themselves may be deliberately produced. 



The animals that will best repay man's observation and 

 experiment and that should, therefore, be selected for that 

 purpose are those that most closely resemble him, on the one 

 hand, in structure and functions, and, on the other, in habits 

 that are most intimately associated with him as com- 

 panions, servants, pets, adopting, as much as may be, his 

 own mode of life. Hence the fittest subject for man's 

 observation and experiment is the dog his constant friend, 

 companion, servant, and plaything; so like him probably 

 by reason of the intimacy of the personal association both 

 in character and habits. 



