from its various component parts, obeying 
the laws of attraction,* and that 
« to reduce my bed-clothes to a single blanket and coverlid, but slept without inconvenience m a large 
« bed-chamber, looking to the north-east, with the window open all night, and with the. door and 
“ windows of an adjacent sitting room also open.—My appetite was keen, and I eat one thud or one 
“ fourth more than before, without feeling the stomach loaded. 
jlnimal heat, therefore, proceeds from the chemical union of certain parts of our food and 
oxygen, modified, and combined, by the proper exercise of the natural animal functions, disen¬ 
gaging caloric , Vide The Philosophy of M^edicine: or, MTdical Extracts on the Nature 
of Health and Disease, including the Laws of the Animal (Economy and the Doctrines 
of Pneumatic Medicine. 
* The Supreme Being has given a force of mutual attraction to the parts ot matter; a principle 
which is alone sufficient to produce that arrangement which the bodies of this universe present to our 
observation. As a very natural consequence of this primitive law, it follows that the elements of 
bodies must have been urged towards each other; that masses must have been formed by their re-union; 
and that solid and compact bodies must have insensibly been constituted; towards which, as towards 
a centre, the less heavy and less compact bodies must gravitate. 
This law of attraction, which the chemists call Affinity, tends continually to bring principles toge¬ 
ther which are disunited, and retains with more or less energy those which are already in combination; 
so that it is impossible to produce any change in nature, without interrupting or modifying this attrac¬ 
tive power. 
Affinity is exercised either between principles of the same nature, or between principles of a dif¬ 
ferent nature. 
We may, therefore, distinguish two kinds of affinity, with respect to the nature of bodies. 
1. The Affinity of Aggregation, or that which exists between two principles of the same 
nature. 
2 . The Affinity of Composition, or that which retains two or more principles of different 
natures in a state of combination. 
of the affinity of aggregation. 
Two drops of water which unite together into one, form an aggregate, of which each drop is 
known by the name of an integrant part. 
An aggregate differs from a heap-, because the integrant parts of this last have no perceptible adhe¬ 
sion to each other; as, for example, a heap of barley, of sand, &c. 
An aggregate, and a heap, differ from a mixture-, because the constituent parts of this last are of a 
different nature; as, for example, in gunpowder. 
The affinity of aggregation is stronger the nearer the integrant parts approach to each other; so 
that every thing which tends to separate or remove these integrant parts from each other, diminishes 
their affinity, and weakens their force of cohesion. 
Heat produces this effect upon most known bodies: hence it is that melted metals have no consist¬ 
ence. I he caloric, or matter of heat, by combining with bodies, almost always produces an effect 
opposite to the force of attraction; and we might consider ourselves as authorised to affirm that it is 
a principle of repulsion, if sound chemistry had not proved that it produces this effect only by its 
endeavour to combine the bodies, and thereby necessarily diminishing their force of aggregation, as all 
other chemical agents do. Besides which, the extreme levity of caloric produces the effect that, when 
it is combined with any given body, it continually tends to elevate it, and to overcome that force 
which retains it, and precipitates it towards the earth. 
The mechanical operations of pounding, of hammering, or of cutting, likewise diminish the affinity 
of aggregation. They remove the integrant parts to a distance from each other; and this new dispo¬ 
sition, by presenting a less degree of adhesion, and a larger surface, facilitates the immediate action, 
