PHARMACEUTICAL SOCIETY, EDINBURGH. 
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animal, and the elements are burned within the animal frame, the sun force developes 
the animal warmth, and becomes the motive agent which enables man and the other 
animals to perform their allotted tasks. The coal is fossil-wood with its store of solar 
force absorbed many ages ago, and the fat and muscle of the animal are aggregations 
of atoms held together by solar force, and suitable for future use. The sun not only 
guides our planet in space, but it raises water in vapour from the ground and surface 
of the sea, and rains it down on upland districts, giving rise to streams, and sup¬ 
plying the running force which moves the water-wheel of the factory. The sun, too, 
causes the motion among the particles of the air which gives rise to local and trade 
winds which move our vessels from shore to shore, and drive our windmills; and 
influencing the waters of the ocean, the sun gives rise to the water-currents so well 
instanced in the Gulf-stream, and to the tides directly and indirectly through the moon. 
The solar orb directs the magnetic and electrical storms which more or less influence 
the earth at all times, and which, probably in an intense degree, as developed within 
the crust of the globe, give rise to earthquake action and volcanoes. In short, the 
sun is the all-motive agency in the physical world. 
We are now in a position to understand the remaining proposition, viz. that the 
food of the animal not only supplies material to build up the living structure and 
to replenish waste, but that it also yields force which can be stored up in the animal 
economy, and used, as necessity may require, in the display of vital energy. In the 
discussion of this subject, it matters little whether we regard life as the mode of activity 
peculiar to certain organized beings, or as the special agency inherent in each organized 
structure ; as in either case life cannot be considered as derivable from physical forces, 
but must be acknowledged to be a mysterious agency implanted in the animal by an 
all-wise Creator, and which directs or controls the matter and force which enter the animal 
economy. 
The physico-chemical conditions which minister as stimulants, have been stated to 
be both external and internal, and the latter are supplied directly or indirectly by 
plants. During its growth, the plant has built up in its structure not only matter, but 
force in the form of chemical affinity, and when the plant is partaken of as food by the 
animal, the matter and the force become available to the animal. Certain of the plant 
elements go to form fatty tissue, which can be stored in the animal frame and form a 
reservoir of fuel which can be burned at a future time ; and part is used directly as 
fuel, so that by its combustion the animal warmth may be sustained. Certain of the 
other compounds of plant matter are elaborated by the animal into muscular and nervous 
tissue, and are stored up as force matter in the animal frame, whilst in other part they 
rapidly undergo changes, and by their disintegration they yield the force exerted by 
the animal. 
These functions which the food of the animal fulfils, are very much the counterpart 
of the processes which occur in an ordinary steam engine. A stock of coal is used in 
the fireplace, which by its combustion supplies the requisite warmth, and a supply of 
water is raised into steam, and gives rise to motive power ; so in the animal economy, 
the elements of food which can form fatty tissue are burned in the animal structure so as 
to supply animal warmth, and the compounds which form nervous and muscular tissue 
are destroyed so as to yield force which is displayed as vital activity. Certain of the 
food compounds undergo change in the blood, and there yield heat and force, whilst 
others are stored up as fatty, nervous, and muscular tissue. In the building up or con¬ 
struction of those parts, heat and force are expended which can only be obtained by the 
destruction of another portion, which may howevey be more or less supplemented by 
external heat. 
The animal system is in a state of incessant motion, and therefore there must be in¬ 
cessant change. The destruction of the animal tissue during the display of the nervous 
and muscular functions, gives rise to the development of force in two ways:—first in the 
passage of matter from the living to the dead state, when the force exerted by the plant 
and the animal in the production of organized tissue is evolved ; and second, in the dis¬ 
integration and separation of the compound atoms of muscle from each other, and the 
resolution of those compound atoms into more simple substances. 
The motive force, therefore, which is exhibited by the animal, is obtained by the 
destruction of muscular and nervous tissue, and the breaking up of similar compounds 
which are flowing in the blood. Labour, which requires the strength of the arm, and 
