32 ANIMAL PHYSIOLOGY. 
more, until finally the machine becomes worthless for the pur- 
pose of its construction. If this mechanism possessed the 
power of adapting from without foreign matter so as to con- 
struct it into steel and brass and arrange this just when re- 
quired, it would imitate a living organism; but this it can not 
do, nor is its waste chemically different from its component 
metals; it does not break up brass and steel into something 
wholly different. In one particular it does closely resemble 
living things, in that it gradually deteriorates; but the degra- 
dation of a living cell is the consequence of an actual change 
in its component parts, commonly a fatty degeneration. The 
one is a real transformation, the other mere wear. 
Had the watch the power to give rise to a new one like itself 
by any process, especially a process of division of itself into two 
parts, we should have a parallel with living forms; but the 
watch can not even renew its own parts, much less give rise to 
a second mechanism like itself. Here, then, is a manifest dis- 
tinction between living and inanimate things. 
Suppose further that the watch was so constructed that, 
after the lapse of.a certain time, it underwent a change in its 
inner machinery and perhaps its outer form, so as to be scarcely 
recognizable as the same; and that as a result, instead of indi- 
cating the hours and minutes of a time-reckoning adapted to 
the inhabitants of our globe, it indicated time in a wholly dif- 
ferent way; that after a series of such transformations it fell to 
pieces—took the original form of the metals from which it 
was constructed—we should then have in this succession of 
events a parallel with the development, decline, and death of 
living organisms. 
In another particular our illustration of a watch may serve 
a useful purpose. Suppose a watch to exist, the works of which 
are so concealed as to be quite inaccessible to our vision, so that 
all we know of it is that it has a mechanism which when in 
action we can hear, and the result of which we perceive in the 
movements of the hands on the face; we should then be in the 
exact position in reference to the watch that we now are as re- 
gards the molecular movements of protoplasm. On the latter 
the entire behavior of living matter depends; yet it is abso- 
lutely hidden from us. 
We know, too, that variations must be produced in the 
mechanism of time-pieces by temperature, moisture, and other 
influences of the environment, resulting in altered action. The 
same, as will be shown in later chapters, occurs in protoplasm. 
