Picture - Cosmic Polymath

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DESIGN IN NATURE
It goes without saying that the ant, the bee, the spider, and the bird cannot build their nests and carry on their
domestic economy as apart from conscious thought any more than men can build houses and cities and institute
governments as apart from conscious intelhgent effort. If consciousness and intelligence withm hmits be demed
the ant the bee, the spider, and the bird, then it is obvious that these attributes must be exercised by the Creator
in and through them. The nest of the ant, the honeycomb of the bee, the web of the spider, and the nest of the
bird are constructed with surpassing skill. They are, in no sense, chance products. On the contrary, they are
paragons of workmanship and design, and the highest resources of mathematics, physics, and mechamcs are not
unfrequently laid under contribution. Consciousness and intelligence are, though to a less degree, present in their
case as they are in man. It is mere evasion to say that an ant, a bee, a spider, and a bird bmld their nests exclu-
sively by instinct, and that a man builds his houses and cities wholly by conscious intelhgent effort. The distinction
is altogether artificial. As there is no difference in the nerve substance of the lower and higher ammak, and no
breach of continuity in the chain which connects the one with the other, it is evident that what holds true of the
highest animals also holds true, within limits, of their lower congeners.
in
I have to express my conviction that conscious reasoning power can be traced in all
their workings, they provide examples of the adaptation of means to ends. Similar
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the lower ammals where,
remarks are to be made
(but in a modified and lower sense) of plants, where no differentiated nervous system exists. The presence of a
nervous system, as we know it, is not necessary to adaptation, and the arranging of means to ends.
The subject of instinct raises the important question of reflex nerve action as it exists in the higher ammals
and in man. As is well known, the nervous system in man is divided into two parts : the cerebro-spinal part, con-
sisting of the brain and the spinal cord plus the sensory and motor nerves, and the sympathetic part, consisting of a
double chain of nerve ganglia extending on either side of the vertebral column plus visceral and other nerve plexuses.
These two parts are united to each other at various points ;
the nervous system in reality being a continuous whole.
There is this pecuharity. The voluntary movements of the body are controlled by the cerebro-spinal portion : the
involuntary, for the most part, by the sympathetic portion. The modus operandi of the cerebro-spinal system is
usually as follows. A sensation due to some external object is transmitted from the peripheral sensory nerves which
travels inwards to the ganglia of the spinal cord, and thence to the gangha of the brain, where it is perceived and
interpreted. The brain in turn sends an impulse, which travels outwards by the motor nerves to the muscles which
are set in motion. The brain can act independently from within, as apart from sensations or impulses transmitted
from without. In other words, the brain, or the mind acting through it, can originate motor impulses similar in
some respects to the sensory impulses transmitted by the sensory nerves and the sense organs. In the case of a
reflex nerve action the sensation, as a rule, only reaches the ganglia of the spinal cord, where it is perceived and inter-
preted ;
a motor impulse being generated and sent on to the muscles by the motor nerves without the knowledge
or co-operation of the brain. The reflex act does not involve voUtion and consciousness in the ordinary sense. It
may occur in the decapitated frog and in man where the brain or the upper part of the spinal cord are diseased, and
where they are functionally cut off or disassociated from the spinal cord as a whole. In such cases, the reflex act
may be largely explained by a nerve habit acquired by constant repetition of acts performed by the entire cerebro-
spinal system during the Ufe of the individual : the spinal cord and sensory and motor nerves being taught to
perform their parts independently of the brain.
The nerve-habit due to the repetition of certain acts becomes after a time automatic, and when once estab-
hshed forms what may be regarded as part of a self-acting machine, which when once set in motion is inchned to
go on indefinitely. This is true of nerve reflexes generally, and of the nerve and muscular arrangements of the
heart, lungs, alimentary canal, bladder, uterus, &c.
The nerve-habit in the higher animals is almost invariably associated with a muscular habit, and it is often
exceedingly difficult to distinguish between the two. The nerves and muscles, as a rule, act conjointly, but they
also, as will be seen further on, act singly and independently. The brain by its motor nerves may send impulses to
the muscles of an amputated or paralysed limb. Similarly, the heart may act without its nerves and as apart from
the brain. The heart of the chick is composed of a mass of nucleated cells with no trace of either nerves or muscles,
yet the organ acts perfectly.
If the sensory nerves be diseased or from any cause paralysed, no sensations reach the brain, and if the motor
nerves be similarly circumstanced no motor impulses reach the muscles. The self-acting machine formed by the
co-ordinated movements of the nerves and muscles must be intact for the performance of cerebro-spinal voluntary
acts. In the case of reflex nerve acts it suffices if a portion of the self-acting machine is unimpaired and in perfect
working order.
The point of transcending interest in this connection is the relation of the reflex nerve acts of the higher
animals to the nerve acts witnessed in the lower animals having a nervous system (with or without a brain) ; it being