1884.] 
Limits to Population. 
1 23 
One of these elements is phosphorus. Without it plants 
cannot grow. Without it the nervous system and the bones 
. 3._ nim als cannot, be formed. Now— borrowing an illus- 
ation from a critique in the “ Chemical News ” — we will 
suppose a planet which contains in its rocks, its soils, and its 
waters, a million ounces of phosphorus in different states. 
Suppose such planet inhabited by a race of beings, each of 
which on an average, contains an ounce of phosphorus in 
its body. The eternity of phosphorus, and of every other 
milT°rV n f tter , n< J t '” thStand , i J ng ’ il is plain that a thousand 
millions of such beings could not co-exist upon the face of 
the planet in question. 
. :t ls , sur ely, then, evident that the limit to population is 
§ Iv ^ n wanhty of certain kinds of matter, their in- 
destructibility being utterly unable to make one ounce play 
the part of two, or of a hundred or of a thousand ounces. 
But we may go very much farther. We cannot live on— 
or, in more technical language, we cannot assimilate— the 
elements such as they exist in the free state, or in inorganic 
combinations in the air, the water, and the rocks g 0 T 
need tor phosphorus has been already referred to. But if 
we take into our stomachs free, pure phosphorus, in its un- 
combined condition, the result is not nutrition, but death. 
Oi suppose we take one of its mineral compounds, such as 
. patite,. a phosphate of lime, or vivianite, a phosphate of 
lion, grind it into the finest powder, and swallow it. Will it 
in any way nourish us ? Will it supply our bodies with the 
phosphorus which they need ? Not in the least. It will be 
excreted just as it was eaten, unchanged and undigested. 
Another essential component of our bodies is nitrogen. 
I he atmosphere, we know, contains a relatively infinite 
supply of nitrogen in the free or elementary state. We take 
tiis nitrogen. into our bodies at every breath we draw: but 
it is not retained and assimilated ; we exhale it again un- 
changed precisely as we drew it in. 
Just the same is the case with carbon, one of the mo^t 
abundant components of our bodies. It exists in the dia- 
mond, in graphite, in anthracite in a nearly pure condition. 
It is found in the air, in the form of carbonic acid. But we 
cannot obtain. the carbon we want by eating graphite or in- 
haling carbonic acid. r 
In like manner we might pass through the whole list of 
substances which go to build up our bodies, and show that 
we cannot obtain them from mineral sources. Our supply 
of all these substances is drawn from the consumption of 
vegetable and animal matters containing them in organic 
