M. L. H. Arnold Snow, M.D.
Relation of Mechanical Vibration to the Nervous Systems
There are certain indications for the vibratory treatment
of spinal nerves and there are conditions and times where and when there is
a question as to the advisability of inducing additional stimulation.
Another point to be considered is how to affect the vaso-constrictors or the
vaso-dilators as desired.
THE TWO GREAT SYSTEMS are the cerebro-spinal
consisting of the brain, spinal cord, and cranial and spinal nerves, -
and the sympathetic, consisting of a connected chain of ganglia
on each side of the spinal column, three plexuses, - cardiac, solar, and
hypogastric, which consist of nerves and ganglia "in front of the spine
in the thoracic, abdominal and pelvic cavities respectively," and of smaller
ganglia in relation with certain viscera, and two kinds of nerve-fibres,
- communicating and distributary. A THIRD SYSTEM, the adrenal
system, is recognized by Sajous and his followers.
Three views [Landois. Text-Book of Human Physiology,
page 621] are held regarding nerve elements. One view is that the
"independent physiological unit of nervous tissue" is the neuron consisting
of "a ganglionic cell with all of its processes. The axis cylinders
of all nerve fibres arise from ganglionic cells and not from a network
of fibres. All nerve fibres terminate finally by means of terminal
arborescences or telodendrites. The nerve cells act as physiological
centers for automatic or reflex movement, for sensation, perception, for
trophic and secretory functions, and the fibres represent a conducting
A second view considers "the fibrillary substance
or the neuropile as the medium of nervous activity. The fibrillary
substance is present in the great mass of gray matter, which represents
a fine lacework or network of nerve fibrils. It can be seen further
in the nerve cells and in the fibres passing off from them."
The third view [Sajous. The Internal Secretions
and the Principles of Medicine, page XI, Vol. II] holds that the nervous
system consists of cells, (the neuron being "not a cell but an organ composed
of many cells), developed and nourished by leucocyte-granulations and traversed
by the oxygen-laden adrenoxidase, and that " the ground substance and Nissl
granules of nerve-cell bodies and the myelin of their axis-cylinders or
nerves are to the nerve-cell what the cytoplasm is to other tissue-cells.
The neuro-fibrils, including those of the axis cylinders, are nerve capillaries
through which the nerve-cells are supplied with oxygen-laden adrenoxidase"
which they receive "from the general circulation through the intermediary
of the ueuroglia fibres (also capillaries) and the neurogliacells which
regulate the volume of plasma admitted into the fibres. The axis
cylinders [Sajous. The Internal Secretions and the Principles of Medicine,
page 927] are the extension in the nerve of the neurofibrils which enter
the dendrites from above and form a mesh work in the cell body (the main
cell of the neuron) and around its nucleus." Sajous thinks "that the myelin
of nerves is a compound rich in phosphorus which, when in contact with
the oxygen-laden adrenoxidase circulating through them, generates nerve-energy"
and "that the ground-substance, the Nissl granules and the myelin in the
cell-bodies of neurons and their dendrites, are also phosphorus-laden compounds
which, when in contact with the adrenoxidase circulating through them,
NERVE FIBRES CLASSIFIED ACCORDING TO FUNCTIONS [Landois.
of Human Physiology, page 677] are:
(1) Centrifugal: (a) motor, (b) secretary, (c) trophic.
(2) Centripetal: (a) sensory, (b) nerves of special
sense, (e) reflex or excito-motor nerves.
(3) Intercentral nerves connecting ganglionic cells.
What concerns us particularly is the NUTRITION of
the nerve as it is affected by various
pathological conditions and the direct bearing of the nerve to stimulation
or inhibition. "That anabolism [Landois. Text-Book of Human Physiology,
page 628] from the blood must take place in the nervous tissue is indicated
by the fact that the irritability of the nerve diminishes after compression
- of the blood vessels, and returns on restoration of the circulation.
The ganglia form much lymph." It has been demonstrated that changes occur
"in the appearance of the cell and its nucleus." [Howell. Text-Book of
The chromatic substance accumulates in the cells
when not active, whereas activity induces its consumption. Vas [Starr.
Organic Nervous Diseases] noted that a mild stimulation caused the
cell to swell and clear up in the center, and Mann showed that functional
activity of the cell is accompanied by an increase in the size due to inhibition
of the lymph lying in the cavity about the cell, the cell at work filling
up the cavity in which it lies. When activity goes on to the point
of fatigue then a shrivelling of the cell begins, first in the nucleus
then in the body." These changes were the result of various stimuli
both electrical and mechanical as running." If a cell that has been
stimulated be given sufficient rest, it will revive and resume its functional
activity but it is necessary that the blood supply be perfect and that
the blood contain the requisite nutrition. There may be an injury
to the neuron of a character which cannot be repaired, which will lead
to organic nervous disease. According to Dr. Starr bacteria as well
as leucocytes may be found in the neuron body and its branches. Howell
[Text-Book of Physiology, page 139] believes the energy to be derived
from "a metabolism which consists essentially in the splitting and oxidation
of the complex substance in the protoplasm of the cell."
THE SPINAL CORD is supplied with blood vessels
which are non-anastomosing terminal arteries. When an embolus occurs
in such an artery "an area of softening" results. Some of the veins
empty their contents eventually into the vena cava, and others into branches
of the jugular.
The spinal cord controls various voluntary and involuntary
actions of the human body. Nerve centers for many of these functions
have been discovered, but others are as yet unknown or are in doubt, some
authorities claiming one and some another region to be the center for a
certain act or impulse, and yet again in some instances experiments have
been made on the lower animals resulting in the discovery of certain centers
which have not as yet been verified in respect to main. Nerve centers
are considered in Chapter VI, and specifically in connection with the consideration
of various organs when their pathological states are discussed.
THE TWO ROOTS OF THE SPINAL NERVES, ANTERIOR AND
POSTERIOR, differ in function.
The anterior roots [Landois. Text-Book of Human
Physiology, page 717] supply centrifugal fibres to:
"1. Striated muscles of the trunk and of the extremities
under the control of the will. Every muscle receives its motor fibres
from several anterior roots and not from a single root, while every root
distributes fibres to a related group of muscles.
"2. Motor fibres to a number of organs provided with
unstriated muscle fibres as urinary bladder, the uterus, vasa deferential
"3. Motor fibres for the unstriated muscles of the
vessels, the vaso-motors.
"4. Inhibitory fibres for the contraction of the
vascular muscles (known only in part): vaso-dilators.
"5. Secretory fibres for the sweat.
"6. Trophic fibres for the tissues."
The posterior roots supply sensory nerves to the
skin and internal tissues except for the face and the anterior part and
inner portions of the head. "They also contain tactile nerves for
the cutaneous surfaces indicated and can convey" irritations exciting reflex
Stimulation of the anterior roots [Brubaker. A
Compend of Human Physiology] causes:
1. Convulsive movements of muscles.
2. The formation of a secretion in glands.
3. Changes in the calibre of blood vessels.
4. Inhibition of the rhythmic activity of certain
Division of these roots is followed by:
1. Loss of muscular movement (paralysis of motion).
2. Cessation of secretion.
3. Cessation of vascular changes.
Stimulation of posterior roots causes:
1. Reflex activities.
2. Conscious sensations.
3. Inhibition of the rhythmic activity of certain
Division of the posterior roots is followed by:
1. Loss of reflex activities.
2. Loss of sensation in all parts to which they are
Sajous' [The Internal Secretions and the Principles
of Medicine, page page XI, Vol. II] view in regard to the spinal system
supported by evidence is embodied in:
"That the pituitary body is the general and governing
center of the spinal system, which includes the gray substance of the base
of the brain, pons, bulb and spinal cord, and the nerves derived from any
of these structures, cranial or spinal, though subsidiary centers are also
present in the bulb and spinal cord."
THE SYMPATHETIC SYSTEM is composed of three cervical,
eleven dorsal, four lumbar and four sacral ganglia, and two [Landois. Text-Book
of Human Physiology, page 718], kinds of fibres (1) medullated supplied
to it as visceral branches by cerebral and spinal nerves, (2) fibres of
Remak which arise from sympathetic ganglia," the medullated fibres being
" (a) sensory; (b) motor for vessels (vasomotors) and viscera, the latter
entering into sympathetic ganglia whence Remak's fibres, as well as medullated
fibres, pass from the ganglion-cells to the innervated areas; (c) inhibitory
fibres and vaso-dilators, in the course of which no sympathetic ganglia
The situation of the ganglia [Belousow. Krause.
Charts of the Nerves of Man] varies in their relation to the vertebrae
in the different regions.
The superior cervical ganglion "is situated
in front of the longus capitis muscle and the transverse processes of the
2nd and 3rd cervical vertebrae. (Gray says that sometimes it extends as
low as the 4th or 5th.) It sends three or four rami communicantes to the
anterior divisions of I to III cervical nerves, a communicating branch
to ganglion nodosum of vagus nerve, a communicating branch to the hypoglossal
nerve, the jugular nerve, the internal carotid nerve." The last three branches
come from the upper part of the ganglion. The following are from
the lower part of the ganglion. The external carotid nerves, pharangeal
branches, laryngeal branches, and superior cardiac nerve. The superior
cervical ganglion connects with the middle cervical ganglion and from this
connection a branch is sent "to the anterior division of the fourth cervical
.nerve." Anteriorly the superior cervical ganglion is " internal to the
sterno mastoid high up."
The middle cervical ganglion "lies at the
level of the 5th or 6th cervical vertebra." It gives off the middle cardiac
nerve, and "communicating branches to the anterior divisions of the 5th,
6th and 7th cervical nerves." Two trunks connect it to the inferior
cervical ganglion. Anteriorly this ganglion is found "behind the
middle of the sterno mastoid."
The inferior cervical ganglion "lies at a
slightly lower level than the middle cervical ganglion." (Gray says: "between
the base of the transverse process of the last cervical vertebra and the
neck of the first rib.") "It sends communicating branches to the
anterior divisions of the 8th cervical and 1st dorsal nerves." (Gray states
7th and 8th cervical.) The inferior cardiac nerve, entering into the formation
of the cardiac plexus, arises "from the inferior cervical and first thoracic
ganglia." Other branches form the subclavian plexus of which "the inferior
thyroid and vertebral plexus are the largest."
The thoracic ganglia number ten, eleven, or
twelve. The first and second thoracic are usually as one; and when
these two are with the inferior cervical ganglion, the number of the thoracic
ganglia is reduced to ten. Most of the thoracic ganglia "lie in front
of the necks of the corresponding ribs. In the middle portion of
the thorax they are slightly more external, in front of the transverse
processes. Lower down they lie closer to the bodies of the vertebrae.
They may be situated nearer the upper border, or nearer the lower border
of the ribs, or in the intercostal spaces." The "greater splanchnic
nerve comes from the 6th to the 9th thoracic ganglia. The roots pass
in front of the bodies of, the dorsal vertebrae. The smaller splanchnic
nerve comes from the 9th to the llth thoracic ganglia."
The lumbar ganglia "lie on the bodies of the
lumbar vertebrae." They usually number five.
The sacral ganglia of which there are four,
or three, lie on the anterior surface of the sacrum,
somewhat internally to the anterior sacral foramina.
The coccygeal ganglion "lies in front of the
anterior surface of the second piece of the coecyx."
The hypogastric plexus lies "in front of the
body of the fifth lumbar vertebra, and of the
promontory, and also in front of the left iliac vein."
Sajous states that the sympathetic system ("general
motor system") has its governing center in the posterior pituitary body
and that it is structurally a part of the general cerebro-spinal system.
He believes that the function of the "sympathetic system [Sajous. The
Internal Secretions and the Principles of Medicine, pages 294 and 1198]
is to transmit efferent impulses and is purely vaso-constrictor, its field
being limited to the small arteries or arterioles, and that it is independent
of the vaso-motor system (whose action is general) being capable, unlike
the latter, of influencing each organ individually, and that its terminals
form part of the mechanism of all organs, and that the specific role of
its terminal fibres is to oppose the strictodilators and restore the arterioles
of an organ to their normal calibre when the functional activity of that
organ is to cease.
His conclusions [Sajous. The Internal Secretions
and the Principles of Medicine, page 294] in regard to the study of
the nerve supply of the voluntary muscles, the salivary, mammary, and cutaneous
glands are as follows:
"The general motor nerves distributed to the organs
above mentioned divide, when near their destination, into two branches:
(1) an 'extrinsic vasoconstrictor' branch, which supplies filaments to
the arteries outside the contractile or secretary - structures of the organ
concerned, and increases the speed of the blood-flow through the latter
during activity by reducing the calibre of these arteries; (2) an 'excito-regulator'
branch, which supplies the intrinsic structures of the organ and governs
their functional activity, and which in turn divides into (a) an excitor
and (b) an intrinsic constrictor branch."
"As the vibratory rhythm of the stream of impulses
transmitted by a nerve always corresponds with that of the structures to
which its terminal filaments are distributed, any variation of vibratory
rhythm transmitted from the cerebro-spinal centers by the general motor
nerves gives rise to a corresponding variation of activity in the structures
or organs supplied by these terminal filaments.
"In all the above-mentioned organs the oxidizing
substances combination of adrenal secretion and oxygen formed in the lungs
and of which the blood plasma is the vehicle - is the physico-chemical
agency through which cellular metabolism is sustained during passive
functional activity, and increased during active functional activity."
He states also "that the volume of blood which circulates
through any organ, whether the latter be in the passive state or functionally
active, is regulated by the joint action of the motor and sympathetic centers
in the posterior pituitary, and that the cranial and sympathetic filaments
to the arterioles owing to the presence in the walls of the arterioles
of spirally disposed muscles, endow these vessels with a special property;
that of increasing the vis a tergo motion of the blood in order to overcome
the resistance of the capillaries."
THE FUNCTIONS OF THE SYMPATHETIC SYSTEM according
to Hall [Sajous. The Internal Secretions and the Principles of Medicine,
page 1185] are:
"1. Cardio-acceleration and cardio-augmentation through
the branches from the cervical ganglia..
"2. Secretory impulses to the salivary glands, the
stomach, the pancreas, the liver, the small intestine, the large intestine,
"3. Vaso-motor impulses, both constrictor and dilator
to all arteries and arterioles.
"4. Motor impulses to the muscular coats of the stomach
and intestines, causing peristalsis and
controlling the pylorus and the cardia of the stomach.
"5. Motor impulses to the muscularis mucosa of the
alimentary canal, causing movements of the
A THIRD SYSTEM is the "ADRENAL SYSTEM" which includes
"the pituitary body, the adrenals and the thyroid gland including the parathyroids."
Sajous' explanation is:
"That the anterior pituitary body is a lymphoid organ
which, through the intermediary of a center located in the posterior pituitary
body and a nerve path in the spinal system, the upper dorsal sympathetic
ganglia and the splanchnic nerves, governs the functional activity of the
"The anterior pituitary body governs, through the
posterior pituitary body, all the oxidation processes of the body.
The center in the posterior pituitary body through which the anterior pituitary
governs the adrenals also controls the functional activity of the thyroid
gland, and thus constitutes the 'adreno-thyroid' center; which is governed
by the test organ (the sensory organ between the two lobes of the pituitary
The adrenal system is "the immunizing apparatus of
the body" and its principal function is to supply an internal secretion
which absorbs the oxygen of the air to carry it to the tissues. It
is the system [Sajous. The Internal Secretions and the Principles of
Medicine, page 231] through which cardiac action, respiration and general
cellular oxidation are maintained. The processes governed by the
posterior pituitary body "include all functions which require conscious
and to a certain extent intelligent co-operation, and are, not mere reflex
phenomena as those elicited from subsidiary nerve centers, in the medulla
and spinal cord."
THE VASO-MOTOR CENTER supplying motor fibres to the
arterial muscles is thought by Landois to be in the medulla oblongata.
This center may be stimulated directly or reflexly. "In animals in
which the center is irritated electrically it has been found that single
induction shocks of moderate strength are effective only when two or three
shocks occur in a second. There is thus a summation of the effects
of the individual stimuli." Ten or twelve strong or twenty to twenty-five
moderately strong shocks per second induce the maximum vaso-constrictor
effects shown by the maximum blood pressure.
"THE VASO-MOTOR NERVES pass from their center in
part directly [Landois. The Text-Book of Human Physiology, page
763] through the tract of some of the cerebral nerves to their distribution:
- through the trigeminus in part to the interior of the eye, through the
hypoglossus to the tongue, through fibres of the vagus to the heart and
in limited number to the lungs and to the intestines. All other vaso-motor
nerves descend in the spinal cord and are connected within the gray matter
with centers of subordinate significance by means of contact. They
make their exit, through the anterior roots of the spinal nerves, then
pass through the visceral branches into the ganglia of the sympathetic
cord. In the sympathetic cord they pass upward or downward and finally
hence either to the vascular plexuses or through other visceral branches
again into the trunks of spinal or cerebral nerves and from these to the
respective vessels." According to Sajous' [The Internal Secretions and
the Principles of Medicine, page 458] view "each general motor nerve
distributed to a part supplies it with its vaso-motor fibres as well as
with all others distributed to it, unless associated with a special nerve,
such as the vagus," and consequently he concludes "that the vaso-motor
center in the medulla must coincidently be that of the general motor nerves
or at least the region where the latter assume vaso-motor functions."
He concludes [Sajous. The Internal Secretions and the Principles of
Medicine, page 463] that there is no individual center in the medulla
to be called "vaso-motor center" and says "the general vaso-dilation after
section of the medulla is due to the interruption of the stream of general
motor impulses through which tonic contraction of the arteries is maintained,
and which the medulla seems to transmit." He thinks the vaso-motors
for the arterioles are from the sympathetic system under control of the
sympathetic center and that the larger vessels are controlled by the bulbar
THE VASO-DILATOR NERVES or vaso-inhibitory nerves
or vaso-hypotonic nerves should be further investigated. Some authorities
(Landois) believe that they exist as special nerves or associated with
vaso-constrictor and other nerves. Sajous states that the functions
of vaso-constrictor and vaso-dilator nerves of muscles are filled "through
the agency of their motor nerves," and that "stricto-dilators "which are
fibres of a cranial motor or secretary nerve (the vagus, facial, etc.),
cause dilation of an arteriole during functional activity, and that the
vaso-constrictor fibres of the sympathetic (whose control is united to
arterioles or small arteries) restore a passive condition. He also
believes that "active vaso-dilation exercised through
vaso-dilator nerves is limited to the arterioles. [Sajous. The Internal
Secretions and the Principles of Medicine, page XII, Vol. II]
"Howell states that "the dilator fibres [Howell. Text-Book of Physiology,
page 597] end presumably in the walls of the arteries, and when sti-inu-.
lated their impulses inhibit - the tonic contraction of this musculature
and thus indirectly bring about a relaxation." Sajous believes that
the vaso-constrictor nerves cause "constriction of the nutrient arteries
of a vessel and vaso-dilation results, the vasomotor nerves become not
vaso-dilators, but stricto-dilators. For a further insight into the
subject of vaso-constrictors and vaso-dilators the reader is referred to
chapter VII. Tables of the vaso-constrictor and vaso-dilator neural
cells are given in Chapter VI.
Stimulation of PRESSOR and DEPRESSOR fibres of "different
afferent nerves" excites or inhibits the action of the vaso-motors.
Loven believes that "the first effect of stimulating every sensory nerve
is a pressor action" and "S. Mayer and Pribram found that mechanical
stimulation of the stomach, especially of its serosa, caused pressor effects."
Sajous thinks "the depressor nerves are those through
which the thyroid center regulates the circulation of the anterior pituitary
body and of the thyroid apparatus."
THE VASO-MOTORS TO THE HEAD ARE MOSTLY FROM the cervical
sympathetic, to the upper extremities "through the anterior roots
of the middle dorsal nerves, into the thoracic sympathetic, and upwards
to the last thoracic ganglion, and from thence to the rami communicantes
to the brachial plexus (Schiff, Cyon)," to the lower extremities
"through the nerves of the lumbar and sacral plexuses into the sympathetic,
and from thence to the lower limbs (Pfluger, Schiff, Cl. Bernard)," to
the skin of the trunk through the dorsal and lumbar nerves, to the
lungs "from the dorsal spinal cord through the first thoracic ganglion
(Brown-Sequard, Fick and Badoud, Lichtheim) to the abdominal viscera
from the splanchnic" (v. Bezold, Ludwig and Cyon). [Landois and Stirling.
of Human Physiology, 4th ed., page 856] A light cutaneous stimulus
lowers the cutaneous temperature, and lessens "the volume of the corresponding
limb, and sometimes causes an increase of the general blood pressure and
change of heart-beat."
The body temperature and even the body weight
are through stimulation of particular vascular areas acted upon by
the vaso-motor nerves. Stimulation of a motor nerve or the spinal
cord causes not only the contraction of the corresponding muscles,
but also dilatation of their blood-vessels, (C. Ludwig and Sezelkow,
Hafix and Gaskell) - the dilatation of the vessels taking place even when
the muscle is prevented from shortening. Gaskell observed under the
microscope the dilatation produced by stimulation of the nerve to the mylo-hyoid
muscle of the frog. Some think that vaso-dilator fibres arise from
all parts of the spinal cord, the ear receiving its supply from the lowest
cervical ganglion and first dorsal. The nervi erigentes from the
sacral plexus when stimulated cause the arteries of the penis to dilate.
(Eckhardt, Loven.) [Landois and Stirling. Text-Book of Human Physiology,
page 863] In applying mechanical vibration take as a guide the rule,
" Stimuli, which are applied at long intervals to the nerve, act especially
on the vaso-dilator fibres, while tetanizing stimuli act on the vaso-motors
(constrictors). The latent period of the vaso-dilators is longer
and they are more easily exhausted than the vaso-motors (Bowditch and Warren)."
MECHANICAL VIBRATION WHEN APPLIED TO AN INFLAMED
NERVE elicits pain if a sensory nerve or contraction if a motor nerve which
may at first be increased or exaggerated. Prolonged application results
in diminution or disappearance of the pain or contraction. It is
of interest to note Tigerstedt's findings. "Tigerstedt [Landois.
of Human Physiology, page 629] discovered that the minimal value of
the mechanical stimulation (induced by the falling of a weight upon the
isolated nerve) is 900 milligram-millimeters, the maximal value from 7000
to 8000. More powerful stimulation causes exhaustion, but this does
not extend beyond the irritated area. The mechanically irritated
nerve does not acquire an acid reaction. A lesser degree of pressure
or tension increases the irritability, which again diminishes after a short
time. The work done by the irritated muscle as a result of this irritation
was as much as 100 times greater than the kinetic energy of the mechanical
nerve irritation. If a mechanical influence acts gradually the nerve
may lose its conductivity or its irritability without any manifestation
of irritation in the process." Heidenhain's tetanomotor, a vibratory
apparatus, is used in investigation work to cause nerve stimulation mechanically.
It will induce "a tetanus lasting up to two minutes. Spinal cord
stimulation may be from interrupted vibration or peripheral nerve stimulation
frictionally. Peripheral stimulation results from local vibrations
with the disc vibratode. Stimulation or inhibition may result according
to the length of time and degree of pressure exerted. The heart may
be slowed or quickened by nerve vibration. It has been demonstrated
that vibration from various devices [Cyriax. Vibrations and Their Effects]
induced muscular contraction (Langendorff and Axenfeld), and stimulatory
effects (Borruttau)." Bechterew and Tschigajew [Cyriax. Vibrations and
Their Effects] by vibrating the whole body induced sleep in about 1/4 hour.
Buchheim obtained stimulatory effects on the sympathetic and vagus in the
neck according to the site of application." Nerve vibration reflexly
affects the activity of organs. "Nebel, Lenmalm and others found
that in some cases paralyzed nerves would react to mechanical (a vibratory
nerve pressing) but not to electrical stimulus." Mechanical stimuli act
when sufficiently rapid to cause a change in the nerve particles.
Their effects vary: if the pressure on a mixed nerve be continuous the
motor fibres are paralyzed sooner than the sensory. If the pressure
be increased gradually an increase of excitability follows to be later
followed by a decrease. According to Kroneeker and Zederbaum pressure
applied to a mixed nerve abolishes reflex conduction before motor conduction.
Fontana, 1758, found that a stimulus increased very gradually caused the
nerve to be inexcitable without showing stimulation signs. A mechanical
stimulus does not cause the nerve to become acid. When a motor nerve
is irritated, the nearer the nerve center the greater the excitability,
that is a muscle that contracts with a given stimulus at a given point
will answer with a greater contraction if the same stimulus be applied
nearer the spinal cord. Reflex contractions [Landois. Text-Book of
Human Physiology, page 633] caused by irritating a sensory nerve "are the
greater the more proximally the irritation is applied." Yet another
point to b noted is that in the same nerve a stronger stimulus is required
for it to act on some muscles as of extensors than on others as flexors,
as has been demonstrated on the sciatic nerve of a frog. The facts
set forth may ultimately aid in estimating the degree of stimulation indicated
for various groups of muscles which it may be advisable to affect.
If stimulation be continuous and excessive, fatigue
followed by exhaustion results. Bernstein demonstrated that "a nerve
trunk is more slowly fatigued than a muscle, but it recovers more slowly"
[Landois and Stirling. Text-Book of Human Physiology, 4th ed., page 683]
which suggests a judicious employment of vibratory stimulation according
to the ease treated, that over stimulation be avoided.
Nerves are capable of carrying impulses even after
there is loss of excitability. We should not stimulate a nerve too
rapidly in order that the nervous impulse may be allowed to travel
without interruption. The impulse travels in a motor nerve at from
"100 to 120 feet per second as found by v. Helmholtz and Baxt" and from
90 to 280 in sensory nerves, as shown by v. Helmholtz. It is less
in the visceral nerves, being but 26 feet in some branches of the vagus
(Chauveau). Reflexes are best induced by 16 stimuli per second.
REFLEX ACTIVITY is considered by some authorities
to be of great importance as it is believed that in chronic visceral diseases
"the spinal muscles lying over the reflexly affected spinal nerve center
will generally be found contracted, and if long coijtinued more or less
atrophied, "and that stimuli" applied directly over the affected center,"
act as a vis a tergo to restore normal functionating power. Interrupted
vibration with the ball used alternately on each side of the spine between
the transverse processes is an effective stimulus.
"Strong stimulation of a sensory nerve inhibits reflex
movements. The reflex does not take place if an afferent be stimulated
very powerfully (Goltz, Lewisson)."
Setschenow distinguished tactile reflexes,
which are discharged by stimulation of the nerves of touch; and pathic
are due to stimulation of sensory (pain conducting) fibres. He and
Paschutin suppose that tactile reflexes are suppressed by voluntary impulses,
and the pathic by the center in the optic lobes.
Jendrassik makes the following subdivision of reflexes:
[Landois. Text-Book of Human Physiology, page 731]
"I. Spinal (tendinous, muscular, periosteal, bony,
articular, genital-muscle). Pathologically manifested as flexor,
less often extensor movement of the lower extremities.
II. Cerebral cortical caused by tickling.
III. Complex from a spinal and a cerebral reflex
center, sneezing, vomiting, swallowing, coughing, evacuation of bladder,
and rectum, and ejaculations."
The following is of interest as regards reflexes:
"1. Reflexes are more easily and more completely
discharged when the specific end-organ of the afferent nerve is stimulated,
than when the trunk of the nerve is stimulated in its course " (Marshall-Hall).
2. A stronger stimulus is required to discharge a
reflex movement than "for the direct stimulation of motor nerves.
3. A movement produced reflexly is of shorter duration
than the corresponding movement executed voluntarily. Further the
occurrence of the movement after the moment of stimulation is distinctly
In connection with the subject of reflexes the question
arises whether the spinal cord is or is not stimulated when we stimulate
the posterior root. "As the spinal cord conduces to the brain impulses
communicated to it from the stimulated posterior roots, but does not itself
respond to stimuli which produce sensations, Schiff has applied to it the
term 'aesthesodie'." Further as the cord can conduct both voluntary
and reflex motor impulses, without, however, itself being affected by motor
impulses applied to it directly, he calls it "kinesodic." Many others believe
that direct stimulation will excite the spinal cord.
Reflex time or the time for carrying impulses by
means of the afferent nerves through the cord to the efferent varies, in
the frog being .0008 to .015 second, but is increased by "almost 1-3 if
the impulses pass to the other side of the cord." It lessens as the
strength of the stimulus is increased "and may even become of minimal duration."
What investigation has demonstrated of the relation
that stimuli bear to effect has been aptly summarized by Kirke acording
to Pfluger as follows:
"l. Law of unilateral reflection. - A slight
irritation of the surface supplied by certain sensory nerves is reflected
along the motor nerves of the same region. Thus if the skin of a
frog's foot be tickled on the right side, the right leg is drawn up.
2. Law of symmetrical reflection. - A stronger irritation
is reflected, not only on one side, but also along the corresponding motor
nerve of the opposite side.
3. Law of intensity. - In the above case, the contractions
will be more violent on the side irritated, but it must not be assumed
that the effect is always ,in proportion to the strength of the stimulus.
4. Law of radiation. - If the irritation (afferent
impulses) increases it is reflected along other motor nerves till at length
all the muscles of the body are thrown into action.
The vagus nerve is particularly worthy of notice
as it has such a wide range of control. "It supplies (1) motor influence
to the pharynx and oesophagus, stomach and intestines, to the larynx, trachea,
bronchi and lung; (2) sensory and in part (3) vaso-motor influences, to
the same regions; (4) inhibitory influence to the heart; (5) inhibitory
afferent impulses to the vaso-motor center; (6) excito-secretory in the
salivary glands; (7) excito-motor in coughing, vomiting, etc."
Scientific conclusions are of importance to all employing
vibratory stimulation of whatever form - static wave current, high-frequency
current, or mechanical vibration. They demonstrate the existence
of factors that are too often overlooked.
VIBRATORY FRICTION acts on nerve endings of both
systems and interrupted vibration acts upon the nerve trunks and
centers. Lightly applied, interrupted vibration stimulates while
stronger or longer fatigues or exhausts the nerves, according to the degrees,
and may affect the blood flow, causing a numbness from diminished nutrition.
Percussion excites "languid" nerves, but if long and vigorous
may over stimulate them and exhaust their ability of perceiving impressions
and allay morbid irritability, a point of therapeutic interest.
LIGHT PERCUSSION at first increases pain, but later
diminishes it, often causing it to finally disappear. The greater
the sensitiveness of the nerve, the less pressure should be at first employed.
VIBRATORY STROKING has a soothing effect and vibratory
friction by acting on the nerve of the blood vessels and lymphatics has
a marked effect on inflammation. It also helps to give the tired
nerves their necessary blood supply.
WHEN DEEP INTERRUPTED VIBRATION, even compressing
in character, is used pressure on the trunk is best made over the "motor
points." Douglas Graham says "it is often surprising how much better
contraction can be obtained from percussion than from a faradic current."
When made on the solar plexus below the xiphoid cartilage and the lumbar
ganglia, situated about two inches on each side of the umbilicus, the patient
should exhale slowly and forcibly, breathing deeply. All abdominal
viscera will be affected
If deep interrupted vibration is applied to the aortic
lumbar plexus the vibratode should be placed about two inches below the
umbilicus. During applications to these regions the patient should
lie on his back, the head and shoulders being elevated, the legs being
flexed. The patient should breathe deeply and during forced exhalation
the pressure should be increased, the vibratode being carried more deeply
at the sites of application. Each impulse should be but for a few
seconds at each site, the period of rest being as long or twice as long
as the time of contact. The vibratodes should be applied but for
three or r times and great care must be exercised that the re is not applied
too suddenly or too heavily, as unpleasant effects, such as nausea and
depression may result.
Deep interrupted vibration with moderate or deep
pressure is stimulating if the application is short, but is exhausting
if too strong or if it be applied too long.
In applying interrupted vibration to the spine place
the ball vibratode over the site of the ganglion and make the pressure
close to the spinous processes and between the transverse processes, or
between the ribs near the spine.
The "chief actions of the sympathetic nerves
on the one hand, and of the cranial and sacral autonomic nerves
on the other, in the regions of double supply" are as follows:
||Effect of Stimulating the Cranial and Sacral Fibres
||Effect of Stimulating the Sympathetic Fibres
||Increase in rate and strength
|Blood vessels of salivary glands and most of buccal mucous
||Dilitation and in certain cases contracture
|Muscular coats of alimentary canal
||Chiefly contraction, sometimes apparent inhibition
||Chiefly inhibition, sometimes contraction
|External generative organs
|Blood vessels of anal mucous membrane and of external