man regards all passing
events as depending on the arbitrary volition of a superior but
invisible power. The tendency is necessarily to superstition. After
reason, aided by experience, has led him forth from these delusions as
respects surrounding things, he still clings to his original ideas as
respects objects far removed, believing the stars to be inhabited by
mysterious powers, or to be such themselves. Gradually he emerges from
star worship as he did from fetichism, still venerating and perhaps
exalting into immortal gods the genii whom he once supposed to inhabit
the stars, long after he has ascertained that the latter are without any
perceptible influence on him.

He is exchanging, by ascending degrees, his primitive doctrine of
arbitrary volition for the doctrine of law. As the fall of a stone, the
flowing of a river, and the ordinary operations of nature familiar to
him have been traced to physical causes, to like causes are at last
traced the revolutions of the stars. In events and scenes continually
increasing in greatness and grandeur, he is detecting the dominion of
law. This perception is extended, until at last it embraces all natural
events, until they are seen to be the consequences of physical
conditions, and therefore the results of law.

'But if we admit that this is the case, from the mote that floats
in the sunbeam to multiple stars revolving round each other, are we
willing to carry our principles to their consequences, and
recognize a like operation of law among living as among lifeless
things, in the organic as well as the inorganic world? What
testimony does physiology offer on this point?'

Physiology, in its progress, has passed through the same stages as
physics. Living beings were once considered to be beyond the power of
external influences, the various physiological functions being carried
forward by a feigned immaterial principle, called the vital agent. But
when it was discovered that the heart is constructed upon the recognized
rules of hydraulics; the eye upon the most refined principles of optics;
that the ear was furnished with the means of dealing with the three
characteristics of sound--its tympanum for intensity, its cochlea for
pitch, and its semicircular canals for quality; and that the air,
brought into the great air passages, calling into play atmospheric
pressure, was conveyed upon physical principles into the ultimate cells
of the lungs, and