760 
PROFESSOR MORTON’S 
must be taken into account the influence of the atmosphere 
which surrounds the earth, and which we and all other sentient 
beings inhale. This, in fact, is the agent or medium by which the 
two grand kingdoms are made reciprocally useful. To the most 
superficial observer it must be obvious that the air is necessary 
to the maintenance of the life of animals and vegetables ; but 
some little acumen is requisite to explain how it is so. This an 
application of chemical laws makes clear. 
The atmosphere essentially consists of one-fifth of a peculiar 
gaseous substance called oxygen, and four-fifths of another pecu- 
liar gaseous substance called nitrogen ; and these are mechani- 
cally mixed together. This may be proved by a simple experi- 
ment. I take a graduated gas jar, taper, trough, phosphorus, 
stand. You perceive that the taper burns freely in this vessel of 
air. I will remove the oxygen from it by burning a portion of 
phosphorus in it, and with which it will rapidly unite. By this 
act we see the proportions in which the two gases are united, 
for the water has ascended up the vessel about one-fifth of its 
dimensions. In other words, the oxygen has been removed and 
the nitrogen remains. 
We will now see whether the taper will burn in this gas. It 
will not. Hence, then, we infer that it is unfit for the respiration 
of man and animals. To the oxygen the air owes its activity, 
its power of supporting combustion, and of purifying the blood 
of animals. Since, then, it is required for these purposes (and 
there are many more hereafter to be spoken of), it must be con- 
stantly undergoing a change, and some source must exist whence 
it again can obtain oxygen; for it has just been said, that no 
formation of new matter ever takes place. 
This source is tiie vegetable world. Animals, by respiration, 
decompose and vitiate the atmosphere; plants purify it by the 
same act. Animals exhale carbonic acid gas, a highly deleteri- 
ous compound ; plants ?7diale this, retain the carbon, which, 
by assimilation, they render a part of themselves, and emit the 
oxygen in a state of great if not absolute purity : and thus two 
of the grand kingdoms of Nature become conducive to each 
other’s benefit. 
Thus, in the neighbourhood of marshy districts and stagnant 
pools, during the fall of the leaf, there is generated a miasm, 
which induces nervous debility (this, in all probability, being 
some of the compounds of carbon or sulphur with hydrogen). 
Persons living contiguous to such places become hypochondriacal. 
They labour under great dejection of mind, and their despondency 
is occasionally so great, that they are both unwilling and incapable 
of undertaking any thing which requires mental exertion. Ilence 
