INSTINCT 105 
insect was swimming its efforts to swim away would be 
performed with much greater vigor. If it does not effect 
its escape by this method it has recourse to a remarkably 
neat and apparently intelligent device. The hind legs are 
thrown back as far as possible, whereby they are enabled 
to grasp the breathing tube a short distance behind the 
body; then by exerting a pull they bend the body ven- 
trally. This soon places the second pair of legs so that the 
offending object can be reached, when all four legs are em- 
ployed to push the body away, which is very frequently 
accomplished. The behavior of a decapitated Ranatra in 
this situation certainly affords an excellent simulation, not 
only of purposive action, but also of considerable ingenuity 
in its accomplishment. 
The reactions of the brainless frog form the stock illus- 
trations of reflex action. The withdrawal of a foot when 
pinched is one of the simplest of these. When a drop of 
acid is placed on one side of the body the hind foot of that 
side is brought forward to wipe it off. With a somewhat 
stronger stimulus the fore leg of the same side may be 
moved back to the irritated spot. If the acid is placed on 
the middle of the posterior part of the back both hind legs 
are employed to remove it. We have here reflexes of a 
higher degree of complexity involving the coérdinated move- 
ments of many muscles. If a frog with the greater part of 
its brain removed is taken in the hands it uses both hind 
legs to push against the hands, and at the same time inflates 
the lungs with air, causing the body to swell so that it more 
readily slips from the grasp. The use of the hind limbs 
and the swelling of the body may be regarded as two com- 
plex reflexes excited by the same cause and which coédperate 
to enable the animal to effect its escape, but the behavior 
may equally well be described as an instinctive reaction. 
