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 conditiéns 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 
