IS79-] 
The Keys of Death. 
213 
less remains of animals. If different samples of wool are 
prepared in the same manner, and dyed together in the 
same pan, some of them will not only be darker in shade 
than others, but even a difference in tone will be occasion- 
ally detected. 
Coming more diredtly to the point, we find certain animals 
feeding heartily upon plants which to other species, and 
especially to man, are decidedly poisonous. Snails and 
slugs devour the leaves of the foxglove as safely, and rela- 
tively in as large quantities, as a cow consumes grass, and 
they are also fond of the Solanacese, including the bella- 
donna. The caterpillars of the following Lepidoptera feed 
upon poisonous plants : — Gonopteryx rhamni upon Rhamnus 
catharticus ; Thais polyxena upon species of Aristolochia ; 
Danais Archippus and Chrysippus upon various Asclepiads ; 
Deilephila Galii , Nicea , and Euphorhice upon species of 
Euphorbia ; Chcerocampa Nerii upon the oleander ; Sphinx 
ligustri upon privet and laurel ; Noctna baja upon belladonna; 
Polia cappa upon staves-acre ; Heliothisa armigera upon to- 
bacco ; and Chrysoptera moneta upon monkshood. Turning 
to the Vertebrates we find that domestic fowls eat the fox- 
glove ; the hornbill consumes with perfedt impunity the 
deadly fruit of species of Strychnos ; whilst the hare and the 
rabbit nibble the belladonna and gnaw the bark of the 
mezereon. 
We are by no means attempting to furnish a catalogue of 
species which feed upon plants noxious or fatal to man, but 
merely give a few of the best-established instances in proof 
that what is poisonous to one species may be to another 
perfectly harmless. There are doubtless poisons which are 
fatal to all. No animal save the serpent which secretes the 
poison has been found able to withstand the venom of the 
cobra. 
In looking over the instances above given, and seeking 
their explanation, we may suppose that the deleterious prin- 
ciples of the plants mentioned may never be really absorbed. 
Like gum and cellulose, they may simply pass along the 
intestinal canal and be rejected with the solid excreta with- 
out ever entering the system at all. But this hypothesis, 
even if demonstrated, would fail to solve the question. We 
should still have to ask, why are these substances absorbed 
in one animal and in others harmlessly rejected? Further, 
in many cases we know that the poison is absorbed. When 
the common viper bites a hedgehog we know that the poison 
enters the blood. What renders it inert, as witnessed in 
