558 
one ‘tissue may be influenced by the nervous system to different 
extents. 
Limitation in the Control of the Nervous System over the 
different Actevities of the Celt.—Even when nervous impulses 
can strikingly affect the vital activity of a tissue, their action is 
limited. They cannot modify the activity in all the various 
ways in which it is modified by the inherent nature of the tissue 
and the character of the surrounding fluid. Thus the sub- 
maxillary gland which pours saliva into the mouth is in life 
ceaselessly taking in oxygen and giving out carbonic acid; it 
does this without pouring forth any secretion. So far as we 
know, no nervous impulse can hasten or retard this customary 
life of the gland by a direct action upon it without producing 
other changes. The nervous system can only do this indirectly 
by modifying the blood supply. The nervous impulse which 
reaches the gland cells causes them to secrete, to take up fluid 
on one side and to pour it out on the other, and it does not, and 
so far as we know it cannot, confine its influence to those 
changes ordinarily going on in the gland cells. The essential 
effect of a nerve impulse appears to be ‘to modify the amount of 
energy set free as work ; usually it causes work to be done, as in 
the contraction of a muscle, or in the secretion of fluid by a 
gland ; sometimes it diminishes the work done, as in the cessa- 
tion of a heart-beat, or the decrease of contraction of a blood- 
vessel. Other changes often go on side by side with this setting 
free of energy as work, but there is no unimpeachable instance ; 
in which these other changes take place by themselves as the 
result of nervous excitation. Physiologists have sought for long 
years in all parts of the body for nerves—calorific or frigorific 
nerves—which cause simply an increase or decrease of the heat 
set free by a tissue; and for nerves—trophic nerves—which 
cause simply chemical changes in the tissue associated with a 
setting free of heat or not. Probable as the existence of such 
nerves seems to be, the search for them cannot, I think, be said 
to have been successful. 
Somatic or Voluntary Tissues.—When we look at the 
question of nervous control subjectively, and consider in our- 
selves what tissues are at our beck and call, we find that we 
have immediate and prompt governance over one tissue only, 
the one which, as we have already seen, is most universally 
supplied with efferent nerve-fibres—namely, the (fibrous) 
striated muscular tissue. The parts of the body composed of 
this muscular tissue we move, as we say, at will. We exercise 
a control over it that we cannot exercise over any other tissue. 
The tissue is supplied with a special system of nerves. In 
other vertebrates there is a tissue of similar microscopical 
characters, and having a similar system of nerves. And we can 
be certain that in all vertebrates the fibrous striated muscle and 
the nervous system belonging to it form a definite portion of the 
body which can be properly placed in a class apart from the 
other tissues of the body. The tissues in this class are spoken 
of as ‘‘somatic”’ tissues, or sometimes, in view of our own 
sensations, as ‘‘voluntary.’’ ‘‘ Voluntary” is not a word which 
physiologists care much to use in this context, because it readily 
gives rise to misconceptions. It will serve, however, if we bear 
in mind that the primary distinguishing characters of the system 
are microscopical, anatomical and developmental ; that other 
tissues than ‘‘ voluntary” can be put in action by the will, 
though in a different fashion ; and that ‘‘ voluntary”’ tissues are 
also put in action involuntarily. That is to say, the word will 
serve if we rob it of much of its ordinary meaning. 
The somatic or voluntary nervous system has in its essential 
features long been known. We may leave it and pass on to a 
more obscure field. 
Autonomic or Involuntary Tissues.—In putting on one side 
the voluntary system, you will notice that we have disposed of 
one only of the several tissues, differing microscopically from 
one another, which go to make up the various organs of the 
body. Of the rest some, as we have said, either do not receive 
nerve-fibres from the brain and spinal cord, or, if they do, 
practically nothing is known about them in our own class of 
vertebrates—the mammalia. These I shall say a word or two 
about later. For the present we must confine our attention to 
the tissues which are known to be supplied not too illiberally 
with nerve-fibres. These are unstriated muscle, and its allied 
cardiac muscle, and certain glands. Since the voluntary striated 
muscle has a nervous system of its own, it might be imag!ned 
that the unstriated tissue and the glandular tissue, differing as 
they do, would also have separate nervous systems. This, 
however, is not the case. The nervous supply of these two 
NO. 1562, VOL. 60] 
NATURE 
[OcTOBER 5, 1899 
tissues have common features and belong to the same system. 
There is, unfortunately, no satisfactory term by which to 
designate it.- On the whole the term ‘‘ autonomic” seems to 
me best adapted for scientific use. But it is not of the first im- 
portance for our present purpose to insist upon a proper 
nomenclature, so that I think I shall not do much harm if I 
use the familiar ‘‘involuntary” for the unknown, or nearly 
unknown, ‘‘autonomic.” 
I need hardly point out how widespread are both the 
glandular and the unstriated muscular tissues. In man practi- 
cally the whole surface of the skin is supplied with sweat- 
glands, lachrymal glands lie hid behind the eye, small glands 
are thick in the respiratory tract from the nose to the smaller 
bronchial tubes, and glands stretch along the whole of the 
digestive tract. Most of these can be set in action by nerve- 
fibres. There are a number of others in which such action has 
not been shown, so that they do not concern us at present. 
Unstriated muscle forming, as it does, part of the walls of the 
arteries and veins, penetrates to every part of the body. It 
forms a large part of the coats of the stomach and intestines ; 
it is present in the spleen and in parts of the lymphatic vessels ; 
it is present in the iris and in other parts of the eye; it occurs 
in greater or less amount in different animals in the deeper layers 
of the skin. 
Consider some of the ways in which these tissues in the several 
organs or structures affect the working of the body. The heart 
contracts and supplies the driving force for the circulation of 
the blood ; the arteries contract less or more, here or there, and 
regulate the amount of the blood to each region; the digestive 
tract secretes solvent and disintegrating fluids in the food, 
churns it into pulp, absorbs some and rejects the rest ; the skin- 
glands pour out their tiny beads of perspiration, and so aid in 
regulating the temperature of the body ; the iris commands the 
aperture of the pupil and determines the amount of light falling 
on the retina; the ciliary muscle, by its varying contraction, 
brings about the focussing necessary for distinct vision. 
But the involuntary tissues do not confine themselves to 
actions of such flagrant utility as those just mentioned. The 
contraction of small bundles of unstriated muscles in the skin 
will cause the flesh to creep; other similar small muscles are 
attached to the hairs; ’tis these will make 
“Thy knotted and combinéd locks to part, 
And each particular hair to stand on end, 
Like quills upon the fretful porpentine.” 
The involuntary tissues, although not under the prompt and 
immediate control of the will, are under the control of the 
higher centres of the brain, They are particularly responsive 
to the emotions ; and in so far as we can call up emotions, we 
can play upon them at will. The ease with which nervous im- 
pulses pass along given tracts depends, amongst other things, 
upon use. And so it appears that our great-grandfathers wept 
and our great-grandmothers fainted with an ease which we 
should require assiduous practice to attain. 
Further, you may note that the contraction of involuntary 
muscle caused by an emotion may in its turn set up nervous im- 
pulses, which pass back to the brain and give rise to vague and 
curious feelings, feelings often lending themselves to effective 
literary expression :— 
““Where our heart does but relent, his melts; where our eye pities, his 
bowells yearn.” 
I must ask your forgiveness for mentioning so many well- 
known facts in the sketch which I have just given of the in- 
voluntary tissues. But I hope it will take from you all excuse 
for not understanding the rest of what I have to say. 
The arrangement of the involuntary nervous system presents 
some peculiar characters. The most distinctive of these is that 
the nerves, after they leave the brain or spinal cord, do not run 
interruptedly to the periphery ; they end in nerve-cells, and the 
nerve-cells send off the fibres which run to the periphery. The 
most direct proof of this lies in the fact that a certain amount 
of nicotine prevents the central nervous system from having any 
influence on the peripheral structures—7.e. the line is some- 
where blocked ; it can be shown, speaking generally, that there 
is no block on either side of the ganglia, so that it must be in 
them. The actual point of attack of the nicotine appears to be 
the connections made by the central nerve-fibres with the 
peripheral nerve-cells. Thus all nerve-impulses, which pass 
from the brain or spinal cord to unstriated muscle or glandular 
tissue, pass through an intermediate station on their way. In 
