460 FRAGMENTS OF SCIENCE. 
functions of his machine from the mere arrangements of 
its organs, as the movement of a clock, or other automaton, 
is deduced from its weights and wheels. " As far as these 
functions are concerned," he says, "it is not necessary to 
conceive any other vegetative or sensitive soul, nor any 
other principle of motion or of life, than the blood and 
the spirits agitated by the fire which burns continually in 
the heart, and which is in nowise different from the fires 
existing in inanimate bodies.*' Had Descartes been 
acquainted with the steam-engine, he would have taken it, 
instead of a fall of water, as his motive power. He would 
have shown the perfect analogy which exists between the 
oxidation of the food in the body, and that of the coal in 
the furnace. He would assuredly have anticipated Mayer 
in calling the blood which the heart diffuses, "the oil of 
the lamp of life," deducing all animal motions from the 
combustion of this oil, as the motions of a steam-engine 
are deduced from the combustion of its coal. As the 
matter stands, however, and considering the circum- 
stances of the time, the boldness, clearness, and precision, 
with which Descartes grasped the problem of vital dynam- 
ics constitute a marvelous illustration of intellectual 
power.* 
During the middle ages the doctrine of atoms had to all 
appearance vanished from discussion. It probably held its 
ground among sober-minded and thoughtful men, though 
neither the church nor the world was prepared to hear of 
it with tolerance. Once, in the year 1348, it received 
distinct expression. But retractation by compulsion im- 
mediately followed; and, thus discouraged, it slumbered 
till the seventeenth century, when it was revived by a 
contemporary and friend of Hobbes of Malmesbury, the 
orthodox Catholic provost of Digne, Gassendi. But, 
before stating his relation to the Epicurean doctrine, it 
will be well to say a few words on the effect, as regards 
science, of the general introduction of monotheism among 
European nations. 
"Were men," says Hume, " led into the apprehension 
of invisible intelligent power by contemplation of the 
works of Nature, they could nev,er possibly entertain any 
*See Huxley's admirable "Essay on Descartes." " Lay Sermons," 
pp. 364, 365. 
