Limitation in lower animals. Effects of age training, race heredity,
individual and racial peculiarities, exhaustion, prostration,
dementia, cerebral congestion, compression, degeneration, narcotics,
ptomaines, toxins. Controlling absorption in another trouble.
Delusions, hallucinations, vice, violence, œstrum, fatigue. Cerebral
source of motions.
These have a much more restricted field in the lower animals than in man
in keeping with the limitation of the mental faculties, and they may
often be traced to demonstrated structural disorder. Yet some emotions
of joy, fear or rage run very high and are comparatively unchecked by
high mental development or mental training. The effect of training is,
however, very marked in the more educated animals.
=Age= modifies by the sobering that comes from experience and habit. The
frolics of puppies, kittens, lambs, foals and calves are in marked
contrast with the sedateness and stolidity of old dogs, cats, sheep or
cattle.
=Training= is seen in the educated horse which would have been panic
stricken at sight of a locomotive, flag or floating paper, at the smell
of a lion or bear, at the sound of a gun or drum, and which will now
boldly face any one of these with no manifest tremor. The emotional
puppy can be trained to soberly fetch and carry, to drive sheep or
cattle without biting, to lie sentinel by his master’s property, to
point at birds without seeking to catch them, or to carry shot birds
without devouring them.
=Race heredity= comes from the training along the same lines in many
successive generations. Thus the more domesticated breeds of dogs
(shepherd, poodle, and greyhound) are very affectionate; other breeds
(bull, mastiff, bloodhound) are lacking in this character. All trained
races take naturally to the occupations of their ancestors. Some
(horses, cattle and sheep) are easily panic-stricken, (stampeded). Some
(turkeys, roosters) are not easily stampeded. Some (skunks), having
effective sources, of defence, have little fear of man.
=Individual and racial mental dullness and torpor= must also be
recognized. Some are stupid and slow, others alert and quickly
responsive. Some horses are not _level-headed_ and become uncontrollable
in difficult situations. Some dogs are so emotional as to endanger their
lives from sudden heart trouble. Some horses, dogs and cats will pine
and die when separated from their fellows or human friends. Extreme
timidity, or sudden rage may be so marked as to constitute a virtual
morbid phenomenon. Sluggish cerebral and mental action may result from
_exhaustion_, _prostration_, or _dementia_; also from _cerebral
congestion_, _pressure_ and _degeneration_; or from _poisoning by
narcotics_, _ptomaines_ or _toxins_ (opium, hyoscyamus, Indian hemp,
dourine, milk sickness, etc.). It may come from profound absorption in
another object, as when the rabid dog bears whipping without a howl.
=Delusions= or =hallucinations= are shown in the rabid dog snapping at
flies, or attacking his friend or master as an enemy, as well as in
other forms of delirium. Narcotics, such as opium, Indian hemp, etc.,
ptomaines, toxins, and (in dogs) essential oils cause delirium by acting
on the nerve centres.
=Vice= in its various forms may become a genuine neurosis, the animal
losing control of its actions.
=Violence= in the form of self-defence or aggression is seen in mares in
_heat_, in bulls or stallions under sexual excitement, in animals roused
by inconsiderate whipping, or in bulls looking on scarlet clothing.
Some high-spirited animals, under extreme fatigue from overwork,
sometimes become violent but resume their docility under rest and food.
In all cases we must know the normal of an individual animal to enable
us to properly appreciate any apparent deviation from the psychic norm.
No less essential is it to take into account the environment and
treatment of the patient.
With regard to localization of cerebral lesions, Sequin thinks emotions
are probably generated in the basal ganglia such as those of the pons
and thalami, while inhibition depends on the anterior cerebral cortical
convolutions.
DIAGNOSIS, SYMPTOMS AND THEIR IMMEDIATE CAUSES. LOCALIZATION OF LESION
IN SPECIAL SYMPTOMS.
Spasm, pain, numbness—irritation. Paresis, paralysis, anæsthesia
(constant)—destructive lesions. Both combined—variable symptoms,
recurrent. Definite, fixed symptoms—structural lesions, usually
progressive. Symptoms, variable as to place, time, subsidence and
recurrence—functional lesions. Brain lesions. Pressure on brain—pain,
spasm, nausea, dullness, blindness, stupor, coma, palsy. Congestion
and anæmia synchronous. Lesions of cortex. Encephalic
lesions—hemiplegia, with spasms, increased reflexes, spasms follow
cranial nerves, vertigo, apoplexy, epilepsy, dementia, coma, little
muscular atrophy, or dermal sloughing. Spinal lesions, paraplegia
without spasm, reflex reduced or nil, follow spinal nerves, head
symptoms less, much muscular atrophy, bed sores. Sensory and motor
tracts, in crus cerebri, respiratory centres—inspiratory expiratory,
inhibition. Salivation, sneezing, coughing, sucking, chewing,
swallowing, vomiting. Cardiac centres, accelerating and inhibitory.
Vaso-motor centre. Spasm centre. Perspiratory centre. Pons. Corpora
quadrigemini, crura cerebri. Thalamus, corpus striatum. Cerebellum.
Cerebral cortex: in ass; in dog. Spinal lesions: lateral half section:
central anteroposterior, vertical section: superior columns: inferior
columns: cervical lateral columns: respiratory tract: glycogenic
centre: pupillary dilator: cardiac accelerator; vaso-motor,
sudoriparous: centre for anal sphincter: for vesical sphincter:
genital centre: vaso-motor and trophic centres: muscular sense tract:
superior column and Goll’s. Table of phenomena from cord lesions.
In =Irritation= of nervous organs the symptoms (spasm, pain, numbness)
are usually _intermittent_.
In =Destructive Lesions= of nervous organs the symptoms (paresis,
paralysis, anæsthesia) are usually _constant_.
When =irritation and destruction= are associated the symptoms are
variable and frequent. The characteristic symptoms of the two may
coexist or succeed each other.
=Structural Nervous Lesions= have symptoms that are definite in their
area of distribution, nature (spasm, paralysis) and permanency.
_Objective Symptoms_ predominate and the case is likely to be
progressive and fatal.
=Functional Nervous Diseases= have symptoms of indefinite distribution,
variable in character, with intermissions and spontaneous disappearances
(as under marked excitement) and subjective symptoms predominate. They
may, however, last for a length of time without change.
Localisation of Brain Lesions.
Lesions of the cranial nerves and their superficial and deep centres of
origin need not here occupy attention. These may be studied in works on
anatomy and physiology. Attention may be drawn rather to the remoter
effects of ganglia which affect or control distant action, and to
general pressure on the encephalon.
=General Pressure on the Encephalon=, whether through fracture of the
cranium and depression of bone, by acute congestion, by blood
extravasation, by inflammatory exudation, or by acute abscess, will
cause pain, spasms, nausea, dullness, blindness, stupor and coma. After
expulsion of the cerebro-spinal fluid from the cranial cavity, the
increasing pressure compresses the blood vessels, reduces or interrupts
the circulation and abolishes the functions in the parts deprived of
blood. Thus congestion of one portion of the encephalon is usually
associated with diminished circulation in another portion. Disorder in
the first may occur from hyperæmia and irritation and in another part
from a consequent anæmia.
=Destructive Lesions of Cortex of One Cerebral Hemisphere= may or may
not cause permanent symptoms, as shown by the passage of a crowbar
through the front of the left hemisphere, yet the man survived for 13
years and showed no loss of intelligence, his disposition and character
alone having changed for the worse. The one hemisphere may by itself
sufficiently control mental acts, while the other lies dormant or may
even have undergone degeneration.
=Diagnosis of Encephalic and Spinal Lesions.= The following may be taken
as guiding principles:
=Encephalic=: Hemiplegic or bilaterally hemiplegic grouping of symptoms.
=Spinal=: Paraplegic grouping of symptoms.
=Encephalic=: Frequent contracture or spasms of paretic muscles.
=Spinal=: Paralysis more perfect and continuous.
=Encephalic=: Reflexes in affected muscles increased: Cerebral
inhibition absent.
=Spinal=: Reflex abolished or reduced in parts the seat of the lesion.
=Encephalic=: Spasms in areas of distribution of cranial nerves (not
spinal.)
=Spinal=: Spasms and paralysis follow distribution of spinal nerves.
=Encephalic=: Head symptoms frequent (vertigo, apoplexy, epilepsy,
dementia, coma).
=Spinal=: Relative absence of head symptoms.
=Encephalic=: Comparative absence of marked muscle atrophy.
=Spinal=: Atrophy in special muscular groups.
=Encephalic=: Little tendency to form bed sores.
=Spinal=: Tendency to form sloughs and bed sores.
Sensory (Æsthesodic) and Motor (Kinesodic) Tracts in Encephalon.
In the crus and above, the sensory tract lies dorso-laterad of the motor
tract, forming about one-fifth of the crus, and extending upward through
a white layer bending inward to form an angle and finally diverging to
the different cortical convolutions. The motor tract is mainly contained
in the inferior pyramids of the bulb, and constitutes the median two
fifths and basal two fifths of the crus. Without entering farther into
this subject it will be observed that lesions of the outer layer of the
crus and its radiating fibres may cause hemianæsthesia of body or head,
including the eye, while lesions of the median and basal layers and
radiating fibres induce hemiplegia of the head, tongue, fore limb, hind
limb, trunk, etc.
=Respiratory Centres, Inspiratory and Expiratory= are in the floor of
the fourth ventricle between the centres for the vagus and accessory
nerves, and are directly stimulated by the CO_{2} in the blood.
Secondary subsidiary centres are in the optic thalamus, in the corpora
quadrigemini both anterior and posterior pairs, and finally in the
cervical spinal cord, so that disorder of respiration may occur from
lesions in these points as well as in the main oblongata centre.
=Respiratory Inhibition= and arrest depend on the vagus, the superior
and inferior laryngeal nerves.
=The Salivation Centre= also lies in the floor of the fourth ventricle
and stimulation of the medulla causes free secretion.
=The Centres for Sneezing, Coughing, Sucking, Chewing, Swallowing and
Vomiting= are also seated in the oblongata, so that any one of these
phenomena may come from a central irritation. In _bulbar paralysis_ the
loss of power usually extends from the tongue through the lips, cheeks,
jaws, pharynx, larynx, to the respiratory muscles and heart. Coughing
may be roused by irritation of the external auditory meatus, liver,
stomach, bowels, or generative organs as well as from the air passages.
=Cardiac Accelerating and Inhibiting Centres= are both present in the
bulb, the latter receiving its afferent impulse mainly through the vagus
nerve. Stimulation of the vagi, anæmia of the bulb through decapitation
or through tying both carotids, hyperæmia through tying of the jugulars,
a venous state of the blood, and blows on the abdomen all slow or arrest
the heart action. Digitalis or muscarin has a similar effect. The heart
action is accelerated by febrile and inflammatory affections, by a high
or low temperature by section of the vagi, by sipping of cold water, by
atropine or curari, and by salts of soda. Potash salts on the other hand
restore the inhibitory action of the vagi and lower the heart’s action.
=The Vaso-Motor Center= is also in the oblongata and the contraction of
the vessels with increase of arterial pressure may ensue from afferent
currents in the sympathetic nerve and many sensory trunks. The varying
activity is seen in blushing, in the congestion of mucous membranes
under rage or excitement, in the capillary contraction in the early
stage of inflammation, in the second stage of capillary dilation, in
angioma or nævus and in extensive congestions and hæmorrhages in
different organs. The arrest of bleeding under fainting is due largely
to the anæmia of this centre.
=A Spasm Centre= the pricking of which causes general convulsions lies
in the medulla oblongata at its junction with the pons. This is excited
by excess of carbon dioxide in the blood, by suffocation, drowning, by
anæmia of the bulb from bleeding or ligature of the carotids, by venous
congestion after ligature of the jugulars, or by the direct application
to the part of ammonia carbonate, or salts of potash or soda. It may
also be roused by afferent nervous currents from different peripheral
parts (spinal cord, sciatic nerve, etc.).
=A Perspiratory Centre= is found in the medulla, on each side, which may
be roused into action by diaphoretics (opium, ipecacuan, tartar emetic,
Calabar bean, nicotin, picrotoxin, camphor, pilocarpin, ammonia acetate,
etc.).
=The Pons= like the medulla is at once a ganglionic and conducting
organ, and its lesions may lead to arrest of nerve currents generated
above or below it, or to the failure to develop currents in its own
centres. Stimulation of its superficial layers may be without effect,
but if this is carried into the centre epileptiform convulsions ensue.
Lesions of one side of its posterior half cause facial paralysis on the
same side and motor and sensory paralysis on the opposite side of the
body (crossed hemiplegia). Lesions of one side of its anterior half
cause paralysis in both face and body on the same side. This depends on
the crossing of the fibres midway back in the pons, which cross again in
the medulla (motor fibres) and in the spinal cord (sensory fibres).
Lesions of the pons are liable to interfere with the functions of the
trigemini, the oculo motor and the superior oblique, and to determine
epileptic movements and loss of coördination of sensorio-motor
movements. Lesions of the superficial transverse fibres (median
cerebellar peduncles) tend to cause involuntary movements to one side.
=Lesions of the Corpora Quadrigemina= cause disturbance of vision,
failure of the pupil to contract to light, blindness, paralysis of the
oculo-motor nerves, and lack of coördination of movements. Stimulation
of one anterior corpus causes rolling of both eyes to the opposite side,
with, if continued, a similar movement of the head and even of the body
(horse in mill, or index motion, or rolling on its axis).
=The Crura Cerebri= are conducting bodies but contain also different
nerve centres. Lesions of one crus cause violent pain and spasm on the
opposite side of the body, followed by paralysis. The oculo motor may be
paralyzed on the same side, but the face and tongue on the opposite
side, owing to the fibres crossing in the pons. There may be turning
movements.
=The Optic Thalamus= transmits sensory currents to the cerebral cortex.
Lesions in this organ cause sensory paralysis on the opposite side of
the body. Afferent currents that do not traverse the thalamus cause
reflexes only. It contains one of the roots of the optic nerve and its
destruction will impair vision. Its injuries may also produce turning
movements.
=The Corpus Striatum= transmits motor currents originating in the
cerebral cortex. Lesions of its interior (lenticular nucleus) cause
motor paralysis and sometimes anæsthesia on the opposite side of the
body. Electrical stimulation of this nucleus causes general muscular
contractions of the opposite side of the body. Irritation of the surface
layers is painless and symptomless.
=The Cerebellum= has been long credited with coördination, and Flourens,
after its removal from a pigeon, found an utter lack of harmonized
movement in walking, springing or balancing. Luciani removed the organ
from a bitch and, after full healing of the part, found a lack of
muscular tone (a cerebellar ataxy), so that no great muscular effort
could be satisfactorily accomplished. After months, marasmus set in and
proved fatal. The lack of coördination is especially connected with
lesions of the vermiform process, those of the posterior portion causing
falling forward and those of the anterior portion, falling backward.
Injury to the middle peduncle on one side causes turning or rolling to
the opposite side. Under slighter injuries there may be only
unsteadiness and staggering like a drunken man. Nausea and vomiting,
with more or less stiffness of the neck or oposthotonos, may be present.
Rolling of the eyes or squinting may occur.
=Focal Cortical Centers of the Cerebrum. Cortical Localization.= Much
has been done experimentally and by observation of morbid lesions to
locate functions in the different convolutions, and though the
subsidiary implication of adjacent and interdependent parts interferes
with a perfectly confident diagnosis, yet certain fundamental facts may
be borne in mind as contributing to a satisfactory diagnosis.
Arloing, on the basis of his own experiments and those of his
predecessors, gives the following as applicable to the equine (ass)
brain:
1. Stimulation of the origin of the front part of the first frontal
convolution, or of the anterior part of the pre-Sylvian convolution,
causes approximation of the feet on the opposite side of the body.
2. Stimulation of the superior part of the first frontal convolution or
of the superior part of the post-Rolandic convolution causes closure of
the jaws and diduction.
3. Stimulation of the anterior end of the upper orbital convolution, or
of the anterior part of the pre-Rolandic convolution, leads to movements
of the nose and upper lip.
4. Stimulation of the antero-superior part of the lower frontal
convolution, or the union of the post-Rolandic with the Sylvian
convolution causes movement of tongue and jaws.
5. Stimulation of the union of the vertical and horizontal parts of the
orbital convolution or frontal lobe, causes opening of the jaws and
bending of head and neck.
6. Stimulation in the front of the union of the frontal and longitudinal
convolutions, or at the union of the Sylvian and second parietal
convolution causes rolling of the opposite eye.
7. Stimulation of union of the frontal and parietal parts of second
parietal convolution leads to closure of both eyelids or, with a strong
current, of lids on both sides.
8. Stimulation of the second parietal convolution, above and a little
behind the extremity of the Sylvian fissure, causes opening of the eye
and adduction of the ear on the opposite side, or, if a very strong
current, on both sides.
9. Strong stimulation of the posterior part of the first and second
parietal convolutions causes tonic convulsions.
10. Currents through the posterior parts of the third and fourth
parietal convolutions gives similar convulsions with violent trembling
of the trunk and members.
In the =Dog’s Brain= localization is easily made by reference to the
crucial fissure which passes outward, right and left, at right angles
with the longitudinal fissure about the junction of its anterior with
its middle third. Also by four parietal convolutions which run backward
from near the crucial fissure, parallel with the longitudinal fissure.
They are counted from without inward. Fritsch, Hitzig and Ferrier have
mapped out the following motor areas:
1. The convolution in front of the outer end of the crucial sulcus
controls the muscles of the neck.
2. The bend of the same convolution backward, opposite the outer
extremity of the crucial sulcus, controls the extensors and adductors of
the fore limb.
3. The convolution just behind the outer end of the crucial sulcus
controls the muscles which flex and rotate the fore limb.
4. The same convolution behind the middle of the crucial fissure
controls the movements of the hind limb.
5. The second convolution back of the crucial fissure controls the
muscles of the face.
6. The anterior part of the internal (4th) parietal convolution, just
back of the crucial fissure, controls the lateral switching movements of
the tail.
7. The posterior angle of the first post-crucial convolution causes
retraction and abduction of the fore limb.
8. The outer end of the first post-crucial convolution, directly behind
the outer end of the sulcus, causes raising of the shoulder and
extension of the fore limb.
9. The anterior end of the third parietal convolution (the second from
the longitudinal fissure) controls closure of the eyelids, the rolling
of the eyeball upward, and narrowing of the pupil.
10. Stimulation of the anterior end of the second parietal convolution
causes partial opening of the mouth with retraction and elevation of its
angle.
11. Stimulation of the point of union of the first and second parietal
convolutions anteriorly causes opening of the mouth with protrusion and
retraction of the tongue.
12. Stimulation of the median part of the second parietal convolution,
causes retraction and elevation of the angle of the mouth.
13. Stimulation of the convolution directly in front of the outer end of
the crucial sulcus causes dilatation of the eyelids and pupil while the
eyes and head are turned toward the opposite side.
14. Stimulation of the convolution behind the crucial fissure causes
contraction of the muscles of the perineum.
15. Stimulation of the convolution in front of the crucial fissure, on
its anterior and sloping portion, causes movements of the pharynx and
larynx (swallowing).
16. Stimulation of motor areas of the cortex, by scraping, irritation,
or disease tends to produce spasmodic contractions of certain groups of
muscles (Jacksonian Epilepsy). Strong stimulation may cause general
epileptiform spasms, which are at first tonic, then clonic. One such
seizure strongly predisposes to a second. If, during an attack, the
cortical centres presiding over a special group of muscles were sliced
off, such muscles relaxed, though the general spasms in the other
muscles continued.
Localizations of Spinal Lesions.
Being at once a conductor between the brain and nerves, and a reflex
nerve centre, we must consider both rôles in seeking to locate lesions
from symptoms. In passing from the nerves to and from the sensorium both
sensory and motor currents cross so that one side of the brain presides
over the other side of trunk and limbs. This crossing of the motor
fibres takes place in the medulla oblongata, while that of the sensory
fibres occurs in the spinal cord close in front of the nerve from which
they have entered.
=Cross-Section of one lateral half of the spinal cord= therefore causes
motor paralysis and rise of temperature of the whole of that side of the
body posterior to the lesion, while it induces sensory paralysis and
cooling on the opposite side of the body up to the same point. A very
limited sensory paralysis on the same side occurs corresponding to the
few sensory fibres passing outward obliquely through the portion injured
by the cross-section.
=A vertical section of the cord separating the one lateral half from the
other= does not necessarily affect the motor currents, while it produces
a limited anæsthesia on each side in the area of distribution of the
nerves, the sensory fibres of which crossed in the seat of the lesion.
=Transverse section of the superior columns= causes hyperæsthesia and
lack of coördination.
=Transverse section of inferior columns=, or of the inferior horn of
gray matter, if close behind the medulla, causes no motor paralysis, but
if farther back induces motor paralysis on the same side of the body.
=Transverse section of the cervical lateral columns= causes motor
paralysis of the lateral walls of the chest (respiratory tract). If the
section is made in the dorsal or lumbar region it is the same as lesion
of the superior columns.
Among =reflex centres= in the cord the following may be named:
The =Respiratory Tract= in the cervical lateral columns just referred
to.
A =Glycogenic Centre= in the anterior cervical section between the bulb
and the fourth cervical nerve.
=Centres which Dilate the Pupil= between the fifth cervical and the
sixth dorsal nerve.
=Cardiac Accelerator Centres= between the three last cervical and the
five first dorsal nerves.
=Vaso-Motor Sudoriparous Centres= in the central gray matter.
=Centre for Anal Sphincter= between the sixth and seventh dorsal nerves.
=Centre for Vesical Sphincter= between the third and fifth lumbar
nerves.
=Genital Centre=, opposite the first lumbar nerve.
=Vaso-motor and Trophic Centres= are found in the inferior horns of gray
matter, and their degeneration causes progressive muscular atrophy.
The =Muscular Sense Tract= is located near the surface of the superior
columns, so that a certain amount of incoördination and unsteadiness of
progression follows its destruction.
The =Deeper Part of the Superior Columns= and the =Column of Goll= which
bounds the superior median fissure control muscular sense and
coördination, and their disease (posterior lateral sclerosis) entails
locomotor ataxy.