COMMON VIPER. 65 
backwards, and the head fixed almost horizontally. In 
an instant the head is, as it were, launched by a sudden 
effort towards the object of its anger, and the erected tooth 
struck into it, and withdrawn with the velocity of thought. 
It is found by experiment that the effect of subsequent 
wounds is greatly diminished either by the diminution of 
the quantity of venom, or by some deterioration of its 
strength; so that if a venomous Serpent be made repeat- 
edly to inflict wounds, without allowing sufficiently long 
intervals for it to recover its powers, each successive bite 
becomes less and less effective. A gentleman of my ac- 
quaintance had some years since received a living Rattle- 
snake from America. Intending to try the effects of its 
bite upon some rats, he introduced one of these animals 
into the cage with the Serpent; it immediately struck the 
rat, which died in two minutes. Another rat was then 
placed in the cage ; it ran to the part of the cage farthest 
from the Serpent, uttering cries of distress. The Snake 
did not immediately attack it; but after about half an 
hour, and on being irritated, it struck the rat, which did 
not exhibit any symptoms of being poisoned for several mi- 
nutes, and died at twenty minutes after the bite. A third, 
and remarkably large rat, was then introduced into the 
cage. It exhibited no signs of terror at its dangerous 
companion, which, on its part, appeared to take no notice 
of the rat. After watching for the rest of the evening, my 
friend retired, leaving the Serpent and the rat together ; 
and on rising early the next morning to ascertain the fate 
of his two heterogeneous prisoners, he found the Snake 
dead, and the muscular part of its back eaten by the rat. 
I do not remember at what time of the year this circum- 
stance took place, but I believe it was not during very hot 
weather. 
