PHYSICAL ANTECEDENTS OF SCIENCE 125

regions which are thus connected with feelings and move-

ments respectively.

What it is especially desirable that the reader should here

carefully note, is the fact that nervous activities which are

accompanied by definite corresponding feelings, shade off, as

it were, into activities which are but occasionally felt, and

into activities which are in no way felt, nor can by any

possibility be felt.

A delicate network of nerves is distributed to the heart,

arteries, intestines, liver, kidneys, etc., which network is

generally spoken of as the "sympathetic system." Usually

the influences which these nerves exercise do not give rise to

sensations, but under some abnormal conditions of any of

these internal organs, such influences may be felt and be

accompanied by pain.

Another notable fact is that exposure to fresh conditions,

it may be the reception of injuries, may result in very

remarkable results, which cannot have been brought about

without the help of that great co-ordinating system of the

body the nervous system. The thickening of the skin of

the hand constantly employed in hard work, and that of the

muscles of the blacksmith's arm or the dancer's leg, are

instances in point ; but most striking of all are the processes

of repair which may take place after injury. Very complex

structures, appropriately formed and nicely adjusted for the

performance of complex functions, may be so developed.

Thus a new elbow joint has been known to be produced

in a railway guard who was compelled to have his own cut

out as a consequence of an injury he had received. The

new joint served his purpose exceedingly well, he having soon

acquired the power of swinging himself by it from one

carriage to another, while a train was in motion, as easily

and securely by means of the newly-formed parts as he could

do with his other, uninjured arm.

regions which are thus connected with feelings and move-

ments respectively.

What it is especially desirable that the reader should here

carefully note, is the fact that nervous activities which are

accompanied by definite corresponding feelings, shade off, as

it were, into activities which are but occasionally felt, and

into activities which are in no way felt, nor can by any

possibility be felt.

A delicate network of nerves is distributed to the heart,

arteries, intestines, liver, kidneys, etc., which network is

generally spoken of as the "sympathetic system." Usually

the influences which these nerves exercise do not give rise to

sensations, but under some abnormal conditions of any of

these internal organs, such influences may be felt and be

accompanied by pain.

Another notable fact is that exposure to fresh conditions,

it may be the reception of injuries, may result in very

remarkable results, which cannot have been brought about

without the help of that great co-ordinating system of the

body the nervous system. The thickening of the skin of

the hand constantly employed in hard work, and that of the

muscles of the blacksmith's arm or the dancer's leg, are

instances in point ; but most striking of all are the processes

of repair which may take place after injury. Very complex

structures, appropriately formed and nicely adjusted for the

performance of complex functions, may be so developed.

Thus a new elbow joint has been known to be produced

in a railway guard who was compelled to have his own cut

out as a consequence of an injury he had received. The

new joint served his purpose exceedingly well, he having soon

acquired the power of swinging himself by it from one

carriage to another, while a train was in motion, as easily

and securely by means of the newly-formed parts as he could

do with his other, uninjured arm.