TRANSACTIONS OF SECTION I. 883 
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, how- 
ever, 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 Inown. We may leave it and pass on to a more obscure field. 
Autonomic or Involuntary Tisswes—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 imagined 
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 tissues has common features and belongs 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 importance 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 practically 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 formsa 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 to pulp, 
absorbs some and rejects the reat; the skin-glands pour out their tiny beads of 
perspiration, and so aid in regulating the temperature of the body; the iris com- 
mands 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, ; ; yowles or. 
.. But the involuntary tissues do not confine themselyes to actions of such flagrant 
utility ae those just. mentioned, ‘The contraction of small bundles of -unstriated 
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