Tropisms and Instincts as Adaptations 411 



In this latter instance it must appear very improbable that 

 we are dealing with an instinct that has been built up by 

 slow degrees on account of the benefit accruing at each stage 

 to the individual. In fact, it appears that the instinct is in 

 this case of really no use at all to the animal, for there can 

 scarcely be any question of an escape by this action. Yet so 

 far as we can judge it is the same instinct shown by other 

 animals, and it is not logical to account for its origin in one 

 case on the grounds of its usefulness, when we cannot apply 

 the explanation in the other cases. If this be admitted, we 

 have another illustration of the importance of keeping apart 

 the origin of an instinct or of a structure and the fact of its 

 usefulness or non-usefulness to the organism. Thus under 

 certain conditions this death-feigning instinct might really 

 be of use to the animal, while under other conditions and in 

 other animals it may be of no advantage at all, and in still 

 other conditions it may be a positive injury to its possessor. 

 Perhaps we need not go outside of our own experience to find 

 a parallel case, for the state of fright into which imminent 

 danger may throw an individual may deprive him for the 

 moment of the proper use of those very mental qualities of 

 which he stands in this crisis in greatest need. 



The peculiar behavior of cattle caused by the smell of blood 

 is another case of an instinct whose usefulness to its possess- 

 ors is far from apparent. It is known that cattle and horses 

 and several wild animals become violently excited by the 

 smell of blood. Hudson gives a vivid account of a scene 

 witnessed by himself, the animals congregating, "and moving 

 around in a dense mass, bellowing continually." Those ani- 

 mals that forced their way into the centre of the mass where 

 the blood was " pawed the earth and dug it up with their 

 horns, and trampled each other down in their frantic excite- 

 ment." 



This action leads us to a consideration of the behavior 

 of animals toward companions in distress. " Herbivorous 



