2i 4 THE GROUNDWORK OF SCIENCE

of speech or gesture) of men on the one hand and of animals

on the other. That we cannot imagine how so fundamental

a distinction arose should be no bar to our recognizing its

existence as a fact. This break, or new departure, in the

order of nature is by no means an isolated one. There is an

absolute break between the living world and the world

devoid of life ; and though it is true that at some period life

for the first time appeared upon the surface of this planet,

whenever it did so appear, there must have been a breach of

continuity and a new departure, which is no whit less certain

because we cannot imagine how it took place. We are con-

vinced there was another breach of continuity and a fresh new

departure when the first organisms appeared which were

capable of sensation.

That all the higher animals " feel " will not be disputed.

They give abundant evidence of sensitivity, and they possess

the special living substance nervous tissue which we know

is the organ of sensation in ourselves. But the world of

plants affords us no such evidence. The movements of the

leaves of some as notably of the sensitive plant and of

Venus's fly trap might be thought so to do, but they are

explicable without sensitivity. That the vegetable world

is devoid of sensation is what should be expected, since

plants are devoid of all trace of a nervous system ; and it

is a universally admitted biological law that structure and

function vary together. If, then, there are any organisms

whatever which do not feel, while certain other organisms

do feel, then (as a gate must be shut or not shut) there

is and must be a break and distinction between the one and

the other.

But it may be objected : " The transition is so gradual, it is

impossible to draw a hard and fast line between sentient and

insentient organisms." Even if this assertion be true, such

an objection would be of no avail, because an apparently

of speech or gesture) of men on the one hand and of animals

on the other. That we cannot imagine how so fundamental

a distinction arose should be no bar to our recognizing its

existence as a fact. This break, or new departure, in the

order of nature is by no means an isolated one. There is an

absolute break between the living world and the world

devoid of life ; and though it is true that at some period life

for the first time appeared upon the surface of this planet,

whenever it did so appear, there must have been a breach of

continuity and a new departure, which is no whit less certain

because we cannot imagine how it took place. We are con-

vinced there was another breach of continuity and a fresh new

departure when the first organisms appeared which were

capable of sensation.

That all the higher animals " feel " will not be disputed.

They give abundant evidence of sensitivity, and they possess

the special living substance nervous tissue which we know

is the organ of sensation in ourselves. But the world of

plants affords us no such evidence. The movements of the

leaves of some as notably of the sensitive plant and of

Venus's fly trap might be thought so to do, but they are

explicable without sensitivity. That the vegetable world

is devoid of sensation is what should be expected, since

plants are devoid of all trace of a nervous system ; and it

is a universally admitted biological law that structure and

function vary together. If, then, there are any organisms

whatever which do not feel, while certain other organisms

do feel, then (as a gate must be shut or not shut) there

is and must be a break and distinction between the one and

the other.

But it may be objected : " The transition is so gradual, it is

impossible to draw a hard and fast line between sentient and

insentient organisms." Even if this assertion be true, such

an objection would be of no avail, because an apparently