INTRODUCTION. 31 



when the season of migration approaches, and beat their 

 heads against the bars of their cages, although it may 

 reasonably be doubted whether quite young birds, which had 

 not yet taken part in a migration, and had been kept from 

 all communication with their fellows, would show a similar 

 desire. Should they even do so as F. C. Noll (p. 22) 

 maintains of the nightingale without having had any pos- 

 sibility of communication with the outer world, it would 

 then be only the inherited tendency to migrate which seizes 

 the animal at the season at which his species migrates, as 

 the result of an inborn and inherited organisation of the 

 brain and nervous system. 



It should the less surprise us that such inherited ten- 

 dencies or habits are found in animals since they are not 

 absent in man ; as many of the phenomena of intellectual 

 life in men show such a great likeness to those of 

 animals, it becomes necessary, if people will insist on the 

 existence of instinct, that the same explanation shall be given 

 of the former as of the latter. But indeed there is no such 

 thing as instinct, in the earlier application of the word, but 

 there is an unbroken series of intellectual gradations from 

 the lowliest animal to the highest man. " Instinct," says 

 Lindsay (" The physiology and pathology of mind in the 

 lower animals," 1871), "is not something separated from 

 and opposed to reason, but is rather a necessary conco- 

 mitant of the latter. Instinct and reason are merely different 

 stages of development, or differing manifestations of the 

 same capabilities, or of the same class of phasnomena. They 

 run into each other by such imperceptible degrees, that it is 

 impossible either to draw a decided line of demarcation, or to 

 find a clearly distinctive character. Instinct, like under- 

 standing and reason, is found both in men and in animals, 

 although in varying degrees or manifestations. It is very 

 difficult to distinguish innate from acquired capabilities, or 

 to separate the results of intuition from those of experience. 

 That which is an acquired capacity or property in the 

 parents, becomes generally an instinct in the following 

 generations, when custom has set on it its seal." 



And the same author (" Insanity in the lower animals ") 

 says again : " I do not doubt that much of that which is 

 called instinct in animals is exactly the same as that which 

 in man is called reason, and has just as good a right to this 



