Hooper, Robert [Editor]: The Anatomist's Vade-Mecum: Containing The Anatomy, Physiology, Morbid Appearances, &c. Of The Human Body ; The Art of making Anatomical Preparations, &c. To which are added Anatomical, Physiological, Medical, And Surgical Examinations For Students (London, 1811)

( ft* )

Tf is greater in living than in dead bodies, and is called the
tone of the muscle.

When a muscle is wounded, touched, or otherw ise irritated,
ft contracts, independent of the will; this power i3 called
irritability, and, by Haller, vis insita; it is a property
peculiar to, and inherent in, the muscles. The parts of our
body which possess t\is property, are called irritable, as the
heart, arteries, muscles, &c. to distinguish them from those
pans which have no muscular fibres.

With regard to the degree of this property peculiar to va-
rious parts, the heart is the most irritable, then the stomach
»nd intestines, the diaphragm, the arteries, veins, absorbents,
and at length the various muscles follow ; but the degree of
irritability depend* upon the age, sex, temperament, mode
of living, climate, state of health, idiosyncrasy, and likewise
upon the uatnre of the stimulus.

When a miwcle is stimulated, either through the medium of
the will, or any foreign body, it contracts, and its contrac-
tion is greater or less in proportion as the stimulus applied ij
greater or lees. The contraction of muscles is different ac-
cording to the purpose to be served by their contraction:
thus, the heart contracts with a jerk; the urinary bladder,
slowly and uniformly : puncture a muscle, and its fibres vi-
brate ; and the abdominal muscles act slowly in expelling the
contents of the rectum. Relaxation generally succeeds the
contraction of muscles, and alternates with it.

The use of this property is very considerable; for upon it
depend all muscular action, and the function of every viscus,
except the nerves,