214 
The Keys of Death . 
[March, 
the experiments of Dr. Lenz ? Morphia if swallowed by 
certain apes enters their circulation, and can be readily 
detected in their urine in large quantities. Why is it in 
them eliminated without occasioning harm ? We note, fur- 
ther, an important distinction : the exemption which any 
animal enjoys from the effects of some particular poison 
may be merely relative, as compared with the adtion of the 
same drug on man, or it may be absolute. To poison a 
hedgehog with cantharides would be as hopeful a task as to 
poison a Neapolitan with macaroni. But when it is loosely 
said that a horse cannot be poisoned with arsenic, or an ape 
with morphia, it is meant merely that these animals can 
endure larger doses than can we without perceptible harm. 
There are cases in which copper — a well-known irritant 
poison — is not merely absorbed, but assimilated, and appears 
even to be an essential of life. Harless detected copper in 
the blood and in the liver of certain mollusks, especially 
cephalopods and Ascidise. His experiments show that it 
“ stands in an essential relation to the blood-corpuscules.” 
Indeed in the blood of the cephalopods there has been de- 
tected an organic copper compound, known as hsemocyanin, 
which fulfils the function due in the higher animals to 
haemoglobin. Von Bibra detected copper on certain crusta- 
ceans, such as Cancer pagurus, and found that it occurred in 
an inverse ratio to the iron which it more or less completely 
replaced. Dr. Genth quantitatively determined the copper 
in the blood of the Limulus, a crab found on the coasts of 
North America. The blood of the healthy females, taken 
just before laying their eggs, was of a deep blue, and when 
dried the incinerated residue contained 0*295 per cent oxide 
of copper, and but a mere trace of oxide of iron. How 
strangely would the appearance of mankind be altered had 
we, like the Limulus , copper instead of iron in our blood ! 
A rich azure would mantle on the cheek of beauty ; we 
should extol in song the charms of sea-green tresses, and 
liken the lips we love not to coral, but to malachite. Per- 
haps the dealers in cupriferous pickles and preserved fruits 
and vegetables are striving to bring about this consum- 
mation. 
Copper in an organic compound named touracin has been 
detected by Prof. Church in the feathers of the touraco. 
That it must consequently be normally present in the blood 
of this bird follows of necessity. 
We may conceive it possible, both as regards disease- 
ferments and poisons properly so-called, that strains o 
