1884.] 
Limits to Population. I2 t 
ments foi his first sales have come in. Just so here. Let 
us take the. single case of phosphorus. Besides the quantity 
contained in the bodies of man and other animals, there is 
a reserve-capital in the soil ; there is a further stock of 
phosphoius in the bodies of the dead and the excreta of the 
living which is being gradually converted into plant-food, 
and there is a further quantity accumulating in the tissues 
of plants, but not available until the crops have reached 
matuiity. All these items form, so to speak, the world’s 
working capital of phosphorus. Is there the remotest pos- 
sibility that this capital is large enough to enable her to 
conduct opeiations a million times larger than those which 
even now appear at times to cripple her resources ? 
As with phosphorus so with combined nitrogen, and more 
or less with all the rarer constituent elements of our 
bodies. 
We have still, however, one important consideration, viz., 
the fa (ft that a very large proportion both of the excreta 
and of the dead bodies of mankind are, so to speak, with- 
drawn fyom circulation. T. he liquid and solid excrements of 
the four million inhabitants of London, together with their 
household refuse of various kinds, are let flow into the sea. 
How long it may be before they can reappear in the form of 
plant-food— much more of human food — it is impossible to 
calculate. 
We have thus shown that the chemical limit of possible 
population depends not. on the “ eternity ” of matter, but on 
the supply of certain kinds of matter as existing in certain 
conditions, which are anything but eternal. 
There is another limit easily overlooked by orators and 
enthusiasts. Every sanitarian knows the difficulty of ob- 
taining, for domestic purposes, a sufficiency of pure water 
untainted by putrescent or putrescible animal matter, Let 
us imagine the population, and consequently the quantity of 
pollution increased a millionfold. How is pure water to be 
procured ? In like manner, how are the excreta of such a 
fearful multitude to be disposed of? Where will be the 
gathering-grounds for water, the irrigation-farms, or even 
the precipitation-tanks, when an uninhabited acre will be a 
rarity ? 
There is a further limit to population, having its seat in 
the organic world. So far we have found that as man in- 
creases, and as the plants and animals which he cultivates 
and protects multiply, there increase also other species 
of plants and animals which are man’s enemies, or, in more 
modern phraseology, his competitors. These enemies either 
