638 TRANSACTIONS OF SECTION I. 
changes in chemical composition of the surrounding medium, are always found 
especially at the front or mouth end of the organism. The chances of an animal 
in the struggle for existence are determined by the degree to which the responses 
of the animal to the immediate environment are held in check in consequence of 
stimuli arising from approaching events. The animal, without power to see or 
smell or hear its enemy, will receive no impulse to fly until it is already within 
its enemy’s jaws. It must therefore be an advantage to any animal that the 
whole of its nervous system should be subservient to those ganglia or central 
collections of nerve cells which are in direct connection with the projicient sense 
organs in the head. This subservience is secured by endowing the head centre 
with a power, firstly, of controlling and abolishing the activities (7.e., all those 
aroused by external stimuli) of allother parts of the central nervous system, and, 
secondly, of arousing these parts to a reaction immediately determined by the 
impression received from the projicient sense organs of the head, and originated 
by some change in the surroundings of the animal which has not yet affected 
the actual surface of its body. 
Education by Experience. 
The factors which so far determine success in the struggle for predominance 
are, in the first place, foresight and power to react to coming events, and, in the 
second place, control of the whole activities of the organism by that part of the 
central nervous system which presides over the reaction. The animal therefore 
profits most which can subordinate the impulses of the present to the exigencies 
of the future. 
An organism thus endowed is still, however, in the range of its reactions, 
a long way behind the type which has attained dominance to-day. The 
machinery we have described, when present in its simplest form, suffices for the 
carrying out of reactions or adaptations which are determined immediately by 
sense impressions, advantage being given to those reactions which are initiated 
by afferent stimuli affecting the projicient sense organs at the head end of the 
animal. With the formation of the vertebrate type, and probably even before, 
a new faculty makes its appearance. Up to this point the reactions of an animal 
have been what is termed ‘ fatal,’ not in the sense of bringing death to the animal, 
but as inexorably fixed by the structure of the nervous system inherited by the 
animal from its precursors. Thus it is of advantage to a moth that it should be 
attracted by, and fly towards light objects—e.g., white flowers—and such a re- 
activity is a function of the structure of its nervous system. When the light 
object happens to be a candle flame the same response takes place. The 
first time that the moth flies into and through the candle flame, it may only be 
scorched. It does not, however, learn wisdom, but the reaction is repeated so 
long as the moth can receive the light stimuli, so that the response, which in the 
average of cases is for the good of the race, destroys the individual under an 
environment which is different from that under which it was evolved. There 
is in this case no possibility of educating the individual, The race has to be 
educated to new conditions by the ruthless destruction of millions of individuals, 
until only those survive and impress their stamp on future generations whose 
machinery, by the accumulation and selection of minute variations, has under- 
gone sufficient modification to determine their automatic and ‘fatal’ avoidance 
of the harmful stimulus. 
The next great step in the evolution of our race was the modification of the 
nervous system which should render possible the education of the individual. 
The mechanism for this educatability was supplied by the addition, to the con- 
trolling sensory ganglia of the head, of a mass of nervous matter which could 
act, so to speak, as an accessory circuit to the various reflex paths already exist- 
ing in the original collection of nerve ganglia. This accessory circuit, or upper 
brain, comes to act as an organ of memory. Without it a child might, like the 
moth, be attracted by a candle flame and approach it with its hand. The injury 
ensuing on contact with the flame would inhibit the first movement and cause 
a drawing back of the hand. In the simple reflex mechanism there is no reason 
why the same series of events should not be repeated indefinitely, as in the case 
