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it one of great interest though difficult to explain. After a time, 
one of them suggested—a suggestion that had before occurred to - 
myself—that this similarity of odours in the animal and vegetable 
kingdoms greatly supported the belief, very generally held by 
naturalists of the present day, that the two kingdoms had sprung 
from a common source. And certainly it is a fact the lower we 
descend in the scale of life, the more nearly they approach each 
other in their organisation, until we arrive at such an extreme 
simplicity of structure as renders it hardly possible to say 
whether it be animal or vegetable. 
But what if we find an imorganic substance having the same 
odour as an animal and a plant? I have mentioned above one 
such substance—viz., the metal arsenium ; and may we not draw 
‘the same inference here as before? If the circumstance of any 
particular odour being found alike in an animal and a plant leads 
to the belief that the animal and vegetable kingdom originated 
from one source, does not the circumstance of the same odour 
occurring in a mineral favour the belief that all the three 
kingdoms—animal, vegetable, and mineral—were united at bottom 
before they advanced on their respective lines of further develop- 
ment? This is in effect as much as saying that formerly, before 
the varied productions of this earth had taken shape, even before 
life had begun to exist, or at least to manifest itself in any 
distinguishable form, mutter existed, but in such an elementary 
state as to give no sign of what was afterwards to arise out of it. 
And now let us proceed to the question—what are these 
odours? Looking to their first origin, we may suppose them to 
have arisen from the interaction of such particles of matter as 
spoken of above, according to their polarity* and environment ; 
chemical affinities also coming into play, from time to time, as 
we see in the chemist’s laboratory—in the case of colours. 
* “ Atoms and molecules are endowed with definite, attractive, and 
repellent poles.”—Tyndall. 
B 
