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THE 



APPLIED ANATOMY OF THE 
NERVOUS SYSTEM 



BEING A 8TUD7 OF THIS PORTION OF THE HUMAN BODY FROM A 

STANDPOINT OF ITS GENERAL INTEREST AND PRACTICAL 

UTILITY IN DIAGNOSIS, DESIGNED FOR USE AS 

A TEXT-BOOK AND A WORK OF REFERENCE 



BY 
AMBROSE L. RANNET, A. M., M. D. 

Profesaor of the AiiAtomy and Physiology of the Nerroiis System in the 

New York Post-Orsduate Medloal School and Horaltal; 

Pkofeaaor of Nervous and Mental Diseases In the Medical Department of the UnlTerstty of Vermont; 

Late Adjunct Professor of Anatomy and Lecturer on the Diseases of the Oenlto- Urinary Organs and 

on Minor Sorgery In the Mealcal DeparUuent of the UnlTeralty of the City of New Tork ; 

Late Surgeon to the Northern and Northwestern Dlspenitarles; 

Resident Fellow of the New York Academy of Medicine ; 

Member of the Medical Society of the Conntr of New York ; 

Member of the Neurological Society of New York: 

Author of a *" Practical Treatise on Surgical Diagnosis.*' *' Practical Medical Anatomy,"* 

"" Electricity in MedidnV' ** The Essentials of Anatomy/* etc. 



SECOND EDITION 
BEWRITTKN, ENLARGED, AKD PROFUSELY ILLUSTRATED 



VTbe greatest thing a human soul ever does in this worid is to see something, and tell what 
he saw in a plain way. Hundreds of people can talk for one that can think, but thousands can 
think for one who can see. To see clearl y is poetry , prophecy, and religion all in one ** 

John Ruseim 






NEW YORK 
APPLETON AND COMPANY 
1888 



• •• • •••••• •••• •• ••• 



0>nm»«T. tm, MM, 
Bt D. AFPLETON AlfD OOXPANY. 



V5I 



So i\)c iSIemors of 

LAFAYETTE RANNEY, A. M., M. D^ 

THIS VOLUME 
18 DEDIOATED BT mS SON, 

THE AUTHOR. 



PREFACE TO THE SEOONP EDITION. 



The author has been prompted by the many favor- 
able reviews of the first edition of this work, and by its 
general adoption as a text-book, to modify its scope and 
plan, with a view of rendering it more worthy of com- 
mendation. It is hoped that its field of usefulness will 
be materially enhanced by the alterations mada 

The changes have been so radical that the present edi- 
tion may be said to be practically a new work. The sec- 
tion on the brain has been entirely rewritten, in order that 
the latest discoveries in the anatomy and physiology of that 
organ should be comprised within its pages. The sections 
on the cranial nerves and the spinal cord have also been 
enlarged, and so altered as to make them more comprehen- 
sive in their scope. Some cuts of the former edition have 
been discarded, and better ones selected as substitutes. 
Many new diagrams have been designed by the author to 
illustrate the text. 

A work upon this field must, of necessity, be to a large 
extent a discussion of others' views. Originality of treat- 
ment of the subject may possibly be claimed for this vol- 
ume (because diagrammatic illustration forms an important 
feature in the author's system of teaching) ; but no work 



vi PREFACE TO THE SECOND EDITIOHT. 

upon this field can be complete without frequent aUnsions 
to, or quotations from, the valuable contributions of the 
more prominent neuro-anatomists, pathologists, and physi- 
ologists. 

The new matter incorporated in this edition as well as 
much of the old edition contains frequent references to 
the writings of many authors, and it is hoped that their 
respective views are now correctly and impartially stated 
at all times. Great care has been exercised in giving full 
credit to those to whose original work the author owes 
much of the valuable information here gathered into one 
volume. 

The aim of the author has been to furnish a reliable 
guide to the student of neurological anatomy and physi- 
ology, in which he may find the views of the leading 
minds in that field accessible, and the main facts which are 
applicable to diagnosis clearly interpreted. It is still pos- 
sible that oversights in acknowledgment may have oc- 
curred, as is very apt to happen in a work of this kind 
(since it is but a publication of lectures delivered before 
classes of students), but, if so, they are unintentional and 
open to correction. 

Much of the new matter of this edition has already ap- 
peared in various medical journals, among which may be 
mentioned the *'New York Medical Journal," the "Medical 
Record," the " Journal of Nervous and Mental Diseases,'' 
and the "Archives of Medicine." Some of these lectures 
have received the unexpected honor of a French and Ital- 
ian translation. 

In the preface to the first edition the author expressed 
his incentive to the effort, as well as his doubts, as follows : 

" The rapid strides, which are being made in the inter- 
pretation of the symptoms of nen^ous diseases, and the in- 



PREFACE TO THE SECOND EDITION. vii 

troduction of many new terms, which must embarrass the 
reader of late monographs, unless he be educated to the 
present standard of knowledge in this field of medicine, 
seem to the author a reasonable ground for belief, that there 
is a demand for a volume, which shall fit the practitioner 
and student to pursue his studies in this special line with- 
out embarrassment, if not with increased interest. 

"With whatever merits or demerits the volume may 
possess, I intrust it to the public, conscious that an effort 
to clear up a field made obscure by visionary theories and 
endless speculation can not but contain some ground to 
which exception may be taken. To what extent it will 
supply the place of a guide in this — the labyrinth of medi- 
cal science — experience alone must decide." 

Finally, the acknowledgments of the author to the pro- 
fession (who have decided in his favor by giving the first 
edition of this work their support in spite of its many im- 
perfections) are now in place. It will be his aim to make 
subsequent editions, if called for, more complete than the 
present one. 

Ambrose L. Ranney. 

156 Madison Aybnub, Nbw York Citt, 
March, 1888. 



TABLE OF CONTENTS. 



GENERAL INTRODUCTION 1-21 

ThB NBBVOUB 8T8TBM OONBIDBBKD AS A WHOLS. 

Its oomponbnt parts. 

Thb obkbbal axioms of nbbtk distribution. 



PART L 
THE BRAIN " 21-327 

Thb OBRBBBO-SPINAL AXIS. 

HlBTOLOGIOAL XLBMBNTS OF NBRYOUS BTRITOTUBBB. 

VaBIBTIBS OF NBBYB OtTRRKNTS : 

Oentripetal or sensory. 

Oentrifagal or motor. 
Functions of nbryb oblls and nxbyx fibxbs: 

Isolated condaotion of impulses. 

Generation and storage of nerve force. 

Discharge of nerve force. 

Storage of various forms of memories. 

Oonsoionsness and mental processes. 
Gray mattbr of brain: 

Tlie cortex cerebri. 

Tlie basal ganglia of cerebnim. 

The cortex cerebelli. 

The tubular gray matter. 

The corpora quadrigemina. 

The gray matter of pons and medulla. 

The various smaller ganglia. 
The cebebrum ...... 27-122 

Whttb mattbr of crrbbrum: 

The commissural fibers. 

The peduncular fibers. 

The associating fibers. 

The fornix fibers. 
Thb projection systems of Mbynbbt and Spitzka: 

Reasons for such an arrangement. 



TABLE OF CONTENTS. 



G^eral formation of projection systems. 
Cranial nerve tracts. 
Ths osrkbbal oobtez: 

Its general constraction, color, thickness, etc 

Its connective tissue (neuroglia). 

Its layers and their special pecoliarities. 

Modifications o^ in different regions. 

The seat of all mental processes and volition. 

TOPOOBAPHT OF OKBEBBAL OOBTBZ: 

Arrangement of its lobes, lobnles, 'fissures, and sulcL 
The classification of its convolutions (Ecker). 

FuVOnOHS OF OKBEBBAL COBTBX: 

The centers of motion. 

Motor center of speech (Broca). 

Centers of hearing, sight, smell, taste, touchy etc. 

Aphasia, as a symptom. 

The motor area, and its subdivisions. 

Cortical motor paralysis. 

Sensory areas of the cortex and their functions. 
Occipital lobes. 

Parietal lobes (posterior to motor area). 
Temporo-spbenoidal lobes. 
Symptoms befbkable to cortical lesions: 

Monoplegia; early rigidity; localized pain; Jacksonian epi- 
lepsy; hemianopsia; word-blindness; word-deafness; motor 
aphasia; paraphasia; monoansnthesia; monospasm; abo- 
lition of memories of various kinds ; hallucinations of vision ; 
vomidng; choked-disk, etc. 

SUMMABT OF THE PHTSIOLOGT OF THE CEBEBBAL COBTEX : 

Its excitable regions. 

Its physiological centers. 

Views respecting cerebral localization. 

Classification of the various monoplegias. 

IHscrimination between destructive und irritative lesions of 
the cortex. 

The storage of varions forms of memories. 

Results of widely diffused lesions of the cerebral cortex. 
Weight avd obowth of the bbain: 

Relative development of component parts. 

Rapidity of growth during different periods of life. 
Ihtba-cebebbal lesions: 

General statements respecting them. 

SuBOIOAL BBABINOS of CEBEBBAL TOPOOBAPHT: 

Guides to the more important cortical centers of cerebrum. 
Late observations of Horsley respecting the niot^>r cen- 
ters. 
Thnne^s method of locating Rolando^s fissure. 
Guides to the fissure of Sylvius. 
Indications and contra-indications for trephining. 



TABLE OF CONTENTS. xi 



Diagnostic stmptoms of mrBA-oEEBBBAL lesions: 

Profoand coma ; hemiplegia ; heniiansssthesia ; late post-para- 
lytic rigiditj; tremor; hemichorea; athetosis; general con- 
vulsions; impairment of special senses; choked-disk, etc. 
The corpus stkiatum ..... 123-132 
Nuclei of corpus striatum. 
Thsib clinical and phtsiolooical importance. 
Fusion of the caudate and lenticular nuclei. 
Cells of each nucleus. 
Lenticular nucleus: 

Its shape, situation, and relations. 
Its fibers. 

Its three members (Glieder). 
Oaudate nucleus: 

Its shape and relations. 
Its cell groups. 

Its afferent and efferent fibers. 
Probable functions of the corpus striatum. 
The optic thalamus ..... 132-161 

The oanolia associated wfth the thalamus. 
The shape and relative development of the thalamus. 
Its anterior and posterior tubercles. 
Its surfaces and their relations to adjacent parts. 
The fibers associated with the thalamus. 
Pbobable functions of the thalamus: 

Ferrier's views; Luys's thalamic centers; Kitties views re- 
specting hallucinations; the relations of the thalamus to the 
optic fibers and the main sensory conducting paths, etc. x 
The orat lining of the third ventricle: 

Inferior optic ganglion; substantia innominata of Reil; an- 
terior pillar of fornix ; bundle of Vicq d' Azyr, etc. 
The internal capsule ..... 161-172 
Relations of the capsule to the basal oangua of the 

cerebrum. 
Subdivisions of the component bundles of the capsule: 
Caudo-lenticular fibers; facial bundle; general motor tract; 
general sensory tract ; speech tract ; optic fibers, etc. 
Methods of research of T6rck, Waller, Fleoiisio, and Guddbn. 
Origin, course, and terminations of the more important 

bundles of the internal capsule. 
Diagnostic symptoms of lesions of the internal capsule: 
Varieties of lesions encountered; hemiplegia; hemianaesthesia ; 
choked-disk; tremor; athetosis; impairment of special 
senses; conjugate deviation of the eyes; clioreiform move> 
ments, etc. 
The corpora quadrioemina .... 172-200 
The anterior and posterior pair. 
The brachia and their relations. 



xii TABLE OF CONTENTS. 

PAOI8 

Fmronovs of antbbiob pais. 

Relations of thssb bodibb to thb visual sense: 

Hemianopsia; probable ganglia of the visual apparatus; intra- 
cranial lesions which may affect sight ; tests for hemianopsia ; 
varieties of hemianopsia ; paralysis, coexisting with hemia- 
nopsia; psychical blindness; cortical area of vision ; crossed 
paralysis coexisting with hemianopsia. 
Thb cbuba cerebbi ..... 200-216 

The obusta obubis ob motob pobtion. 
The tbomentum obubis ob sbnsobt pobtion. 
The substantia nioba. 

The ganglia of obioin of the tegmental fibebs. 
The P08TEBI0B longitudinal fasoioulus. 
The lemniscus tbaot. 
The fobmatio bbtioulabis. 
Fibebs of the bupebiob obbebellab peduncle. 
Fibebs fbom the post-optio ganglion. 
The genioulate bodies. 
The bed nuclei of Stilling. 
The mamdllabt tubebcle. 
The pineal gland. 
The cebebellum ...... 216-243 

Oenebal anatomy and bblations of the oebbbellum. 
cobtbx of the cebebellum. 
White substance of the cebebellum. 
Pbojeotion systems OF cerebellum. 

Gbat masses indibectlt oonneoted with the cebebellum: 
Red nuclei of Stilling in the tegmentum. 
Olivary bodies of the medulla. 
Ganglia of the pons Varolii. 
Peduncles of the cerebellum: 
Processus ad cerebrum. 
Processus ad pontem. 
Processus ad medullum (restiform body). 
Relations of cebebellum to cranial nerves. 
Pbobable functions of the cebebellum: 

An organ of coordination ; relations to visual perceptions ; re- 
lations to tonic muscular contractions ; views of Mitchell, 
Spencer, Spitzka, and others. 
Diagnostic symptoms of cebebellab lesions: 

Cerebellar ataxia; vertigo; titubating gait ; staggering; gas- 
tric crises; anarthria; occipital pain; nystagmus; ambly- 
opia ; choked-disk ; amaurosis ; rotary movements, etc. 
The PixriTABY body ..... 243, 244 

Its general appearance and construction. 
The MEDl'LLA OBLONGATA AND PONS VaBOLII . . 244-307 

FoBM and fissures op medulla. 
Subdivisions of medulla (Erause). 



TABLE OF CONTENTS, 



ChAVOBS m ORAT MATTER FROM THAT OF SPINAL OORD, DUB TO 

FORMATION OF FOURTH YENTRIOLS. 
ThB ORAT MATTER OF THE MEDULLA AND PONS: 

Cranial nerve ouolei. 
Accessory nerve nnclei. 
Superadded gray matter. 
Reticnlor ganglion (Spitzka). 
Upward continuation of thb artxriob horns of the spinal 
cord: 

Nnolens of the pyramid ; nnclei of lateral column ; hypoglossal 
nnclens; abdncens nucleas ; motor-oculi nucleus. 
Upward continuation of the posterior horns of the spinal 
cord: 
Substantia gelatinosa ; reticular ganglion. 
Upward continuation of the central orat of the spinal 
cord: 

Posterior spinal accessory nucleus ; nuclei of ninth, tenth, and 
eleventh cranial nerves ; lining of fourth ventricle ; aqueduct 
of Sylvius. 

AOCESSOBT nuclei OF THE MEDITLLA : 

Inferior facial nucleus; accessory nuclei of the spinal acces- 
sory and hypoglossal nerves; the acoustic nuclei. 
Superadded or at matter of the medulla and pons Va- 
rolii : 

Triangular nuclei ; davate nuclei ; olivary bodies ; parolivary 
bodies; nuclei of the pyramids; middle sensory nucleus of 
the trigeminus; red nuclei of Stilling; geniculate bodies, 
etc. 
The white surstanoe of the medulla and pons: 

General classification of the fibers. 
The ptramidal tracts: 
Their accessory fibers. 
Their course and function. 
Upward continuation of the anterior root zones of thb 
spinal cord: 

Fibers of the formatio reticularis; posterior longitudinal bun- 
dles ; portion of the fillet or lemniscus tract (?). 
The fillet or lemniscus tracts: 

Its two bundles — motor (?) and sensory. 
Its relation to motor-ocnli nerve. 
Its relations to the triangular and clavate nucleL 
Its probable function. 
The direct oebebellar tracts: 

Association with the vesicular column of Clarke. 
The probable termination of these fibers. 
Probable function of these fibers. 
Continuation upward of Burdaoh's and Goll^s columns: 
The nuclei of these columns; ascending root of fifth nerve; 
round bundle or the " respiratory bnndle ^^ (Krause). 



XIV 



TABLE OF CONTENTS. 



ThB 8ENB0RT TRACTS TO THE CEREBRUM: 

Researches of Flecbsig, Voo Monakow, Starr, etc 

Reticalar formation. 

The fillet tract 

Paths for sensations of pain, toacb, and temperature. 

Path for the muscular sense. 

Relations of these paths to the cerebellum. 

The sensory or *^ pinniform " decussation. 
The sttperadded fibers of the pons and medulla: 

The fibers of the superior, middle, and inferior cerebellar 
peduncles. 
DulOnostio symptoms of lesions of the pons: 

Grossed facial paralysis; crossed hemianesthesia; anarthria; 
convulsions; conjugate deviation of the eyes; contraction 
of the pupil ; deafness ; disturbances of respiration and cir- 
culation ; unilateral ataxia, etc. 
Functions of the medulla: 

A great refiex ganglion ; the special physiological centers situ- 
ated within it; nervous circle of deglutition; nervous mech- 
anism of respiration; nervous mechanism of circulation; 
vaso-motor center of the medulla, etc. 

DiAONOSTIO symptoms OF LESIONS OF THB MEDULLA: 

Impairment of speech, deglutition, and circulation; diabetes; 
albuminuria; loss of power of protrusion of tongue; Du- 
chenne's disease ; bilateral paralysis of arms and legs ; uni- 
lateral ataxia; vaso-motor disturbances, etc. 
Thb ventricles of the brain .... 

Their general situation, shape, formation, and ependvma. 
The chief commissures of the brain . 
Corpus callosum. 
The fornix. 

Commissures of the third ventricle. 
The membranes of the brain .... 
The dura mater. 
The arachnoid. 
The pia mater. 
Blood-vessels of the brain .... 
The carotid system and its branches. 
The yebtrbral system and its branches. 



307-314 
314-316 

316-321 

321-327 



PART II. 

THE CRANIAL NERVES ..... 329-533 

Enumeration of the nerves from before backward. 

The deep origin and nuclei of the twelve separate nerves. 
The olfactory nerve . . . . • 341-349 

Its oRioiN and construction. 

The PECUUARITIB8 OF rrs filaments. 



TABLE OF CONTENTS. 



XV 



ThB limits of its DISTBIBnTION. 

The phtbioloot of olfaotion. 

ThS act of 8NBBZINO. 

ReFLKZ acts DXPENDRNT upon THB OLFACTORY NEBYB. 
FUNOTIONB OF OLFAOTORT NBRVB IN ANIMALS. 
RbLATIONB OF THB 8BN8B OF SMELL TO THAT OF TA8TB. 
CUNIOAL POINTS AFFORDED BT THB OLFAOTOBT NERVE. 

" Hyperosmia," its tests and causes; *' anosmia,*' its tests and 
oaoses. 
The optic nerve . . . . . • 349-373 

The optic tracts, their origin and attachments. 
The optic chiasm, its construction and phtsioloot. 
Distribution of optic nerve. 
Reflex acts excited bt optic nerve 
Decussation of optic fibers and its phtsioloot. 
Relations of the optic nerve in the obbit. 
Anatomical defects of vision and theib consequences. 
*' Hjrperopia,*' its tests, caases, and results; ** myopia," its 
tests, oansea, and results ; *^ astigmatism," its tests, caases, 
and results. 
Changes observed in the pupil. 

Dilatation, its caases and physiology ; contraction, its caases 
and physiology. 
Visual sensations and their modifications. 

MasciB volitantes; the ^*hlind spot" of the retina; insensibil- 
ity of the retina after firm pressure. 
The perception of color. 

Visual purple and its probable fimctions ; rods and cones of 
the retina; Young-Helmholtz theory of color vision ; limits 
of different color perceptions ; color blindness. 
Apparent vision of objects not bballt seen. 

Its causes. 
Effects of optic' nerve on co()bdinatioh. 

Qoltz*s experiments. 
Effects of optic nerve on the lachbtmal appabatub. 

The act of winking the eyelid ; effect of closure of eyelid upon 
the lachrymal canals. 
Olinical points afforded bt the optic kebvx. 

Hemianopsia, temporal, its causes; hemianopsia, nasal, its 
causes; hemianopsia, bi-nasal, its causes; hemianopsia, bi- 
temporal, its causes ; amaurosis ; hypenesthesia of the optic 
nerve; amblyopia; atrophy of optic nerve. 
The motor-oculi kerve ..... 373-395 
Its origin, course, and distribution. 
The physiology of contra cnoN of the pupil. 
Physiological reasons fob the distbibution of the thibd 

NEBVE. 

Mechanism of the dilatation of the pupil. 



XVI 



TABLE OF CONTENTS. 



MOYBMEKTS OF THE EYEBALL. 

DUlONOSTIO attitudes of the head in ocular PABE8I8. 

GUNIOAL POINTS PEBTAININO TO THE THIRD NEBVE. 

Megalopsia or maoropsia ; mioropsia; ptosis; motor-ocnli pa- 
ralysis ; strabismus. Diseases of the ocular muscles : nystag- 
mus; iritic spasm; contracture; paralysis; tabetic condi- 
tions; diplopia; strabismus. 
The trochleab ob pathetic nerve . . . 395-397 

Its supebfioial and deep points of origin. 
Its course and relations within the cranium. 
Its points of ounical interest. 
The tbioeminus nebve . • . . . 397-421 

Itb superficial and deep points of origin. 
Course of its sensory and motor roots within the cranium. 
Its afferent and efferent fibers. 
The effects of section of the nerve. 

On sensation ; on mastication ; on taste; on hearing; on sight; 
on smell. 
Olinical points pertaining to the trigeminus nerve. 

Neuralgia (tic-douloureux) ; spasm of the trigeminus; paraly- 
sis of its individual branches. 
Diagnostic value of the trigeminus nerve. 

Bleaching of the hair; immobility of temporo-maxillary joint; 
furring of the tongue ; ulceration of the cornea ; ulceration 
of the auditory canal ; earache ; pain in the scalp ; conjunc- 
tival distribution. 
Surgical anatomy of its main branches. 

Section of the supra-orbital nerve ; section of the supra-maiil- 
lary nerve ; section of the inferior-dental nerve. 
The ganglia connected with the trigeminus nerve. 

Ophthalmic, lenticular, or ciliary ; sphcno-palatine or MeckoPs ; 
otic; sub-maxillary. 
The abdugens nebve (motor-oculi externus) *. . 421-423 

Its superficial and deep points of origin. 
Its relation with the ophthalmic ganglion. 
Its ounical relations. 
The facial nerve ...... 423-444 

Its superficial and deep points of origin. 
Its course and distrirution. 
Phtsiologt of rrs main branches. 

The petrosal nerves; the chorda tyrapani nerve; the "pars 
intermedia^' of Wrisberg; the tympanic branch; the facial 
branches; the muscular branches. 
Its communications with other parts. 

Branches joining the fifth nerve ; branch to the otic ganglion ; 
branch to MeckePs ganglion ; sympathetic fiber* ; its rela- 
tion to deglutition and speech ; its relation to smell; its re- 
lation to hearing; its relation to respiration. 



TABLE OF CONTENTS. 



xvii 



Its FiLAMSirrs of DisTBiBUTioy. 

Physiological relation to deglutition ; physiological relation to 
facial expression ; physiological relation to mastication. 

OUNIOAL POINTS PEBTAININO TO THB NBBYB. 

Spasm of the facial muscles. BelFs paralysis : intra-cranial va- 
riety ; auditory variety ; rheumatic variety ; traumatic vari- 
ety ; syphilitic variety ; diphtheritic variety ; iiEicial diplegia. 
The auditory nerve ...... 444-466 

Its sufbbfioial and deep points of origin. 

Anatoiooal stbuotube and PEouLiABmES OF rrs filaments. 

Its ooubsb and distbibution. 

Functions of its various bbanohes. 

The mechanism of audition. 

External ear, its construction and functions ; middle ear, its con- 
struction and functions. Internal ear, its construction and 
functions : the semicircular canals ; the vestibule. The coch- 
lea : its scales ; organ of Oorti ; membranes and ligaments. 

CUNIOAL POINTS PEBTAININO TO THE NEBVE. 

Auditory vertigo — " Menidre^s disease " ; injuries to the semi- 
circular canals. Neuroses of the auditory nerve : acoustic 
hyperffisthesia ; acoustic ansssthesia. 
The olosso-pharynoeal nerve .... 466-482 
Its supebfioial and deep points of obioin. 
Its oanouonio enlargements. 
Its ooubse and belations. 
Its effebent ob motob pibebs. 
Its affebent ob sensobt fibebs. 
Its fibebs of taste. 
Effects of section of the nbbve. 

On special sense of taste ; on deglutition. 
Mechanism of the act of DEOLUTrrioN. 

First period ; second period ; third period ; nerves involved ; 
importance of soft palate ; the nerve center for the act. 

CUNIOAL POINTS PEBTAINING TO THE NERVE. 

Glosso-labio-laryngeal paralysis — Duchenne^s disease ; hyper- 
geusia; ageusia! 
The PNEUM00A8TRIC nerve. .... 482-fi05 

Its supebfioial and deep points of obigin. 
Its intimate affiuation with the glosso-phabtnoeal nebve. 
Its ganglionic enlargements. 
The inherent fibers of its trunk. 
Its branches of distribution and their functions. 

The pharyngeal branches : effects on deglutition ; effects on 
voice. The laryngeal branches: their relation to phona- 
tion ; their relation to respiration ; their relation to spinal 
accessory nerve. The branches to alimentary canal : their 
relation to peristaltic action ; their relation to secretion. 
The cardiac branches: depressor nerve of hearths action; 
2 



xvm 



TABLE OF CONTENTS. 



efifects of galyanism. Vaso-motor fibers: effects on blood- 
vessels. The pulmonary branches : their relation to respi- 
ration — acceleratory fibers; inhibitory fibers. 
Ths ooubsb and relations of the nebye on each side of 

THE BODY — 

With carotid artery ; with jognlar vein ; with oesophagus; with 
the lungs ; with the abdominal viscera. 

EfFEOTB of SECTION OF THE PNEUMOQASTRIO TRUNK. 

Upon the larynx; upon the lungs; upon the heart. Upon the 
digestive tract : stomach ; liver ; intestinal canal. 
Clinical points pertaining to the nerve. 

Pharyngeal ansssthesia; pharyngeal spasm ; pharyngeal paraly- 
sis; laryngeal spasm (Kopp's asthma); whooping cough; 
aneurysmal cough ; pulmonary asthma ; pulmonary vaso-mo- 
tor paralysis ; angina pectoris; cardiac neuralgia ; gastrodyn- 
ia ; boulimia ; polydipsia ; dyspeptic vomiting ; polyphagia. 
The spinal accessory nerve .... 
Its superficial and deep points of origin, 
i"^ course and distribution. 
Its filaments of communication. 
Its relations to the production of voice. 
The effects of section of the nerve. 

On phonation; on respiration; on deglutition; on the action 
of the heart ; on singing. 
Clinical points pertaining to the nerve. 

Tonic spasm of sterno-mastoid muscle ; tonic spasm of trape- 
zius; clonic spasm of sterno-mastoid and trapezius mus- 
cles; salaam convulsion of Newnham; unilateral paralysis 
of sterno-mastoid and trapezius muscles ; bilateral paralysis 
of sterno-mastoid and trapezius muscles. 
The hypoglossal nerve (sub-lingual nerve) . 
Its superficial and deep points of origin. 
Its course and distribution. 
The descedens noni branch. 

Functions of the nerve : on deglutition ; on articulation. 
Clinical points pertaining to the nerve. 

Dnchenne^s disease : abnormalities of speech ; abnormalities of 
voice; impairment of deglutition ; facial deformity; lingual 
tremor. Lingual spasm : lingual paralysis. 



605-618 



618-632 



PART III. 



THE SPINV- CORD ...... 

Its anatomical construction, functions, and clinical bear- 
ings. 
Its cervical and lumbab enlargements. 
Its fissures and columns. 



633-638 



TABLE OF CONTENTS. xix 



Its nerves (their roots and general construction). 
Its membranes and the cerebro-spinal fluid. 

Their faoctions and sitaation. 
Blood-vessels of the cord. 
Vbrtebrje as guides to spinal segments. 
Histological elements of the cord. 
Appearance of a transverse section of the cord. 

Its gray matter; its white matter; its central canal; its 
commissares. Pathological sabdi visions of the cord : col- 
umns of Goll; columns of Burdach; columns of Ttlrck; 
fundamental columns ; direct pjramidal columns ; anterior 
root zones; posterior root zones; crossed pyramidal col- 
umns ; direct cerebellar columns. 
Functions of the spinal cord. 
(1) Organ of conduction. 

Paths of motor impulses; paths of sensory impulses; 
commissural fibers. Fibers of the spinal cord : motor 
fibers and their function; sensory fibers and their 
function ; commissural fibers and their function. 
(S) Spinal cord as a nerve center. 

Reflex action of the cord ; automatic action of the cord ; 
vaso-motor centers ; cilio spinal center ; genito-uri- 
nary center ; tonic action on muscles ; center of defe- 
cation ; center of parturition ; center of micturition ; 
center of erection. 
(5) Organ of coordination of muscul^ir motements. 
Clinical points pertaining to the spinal cord. 

The kinesodic system ; the ssthesodic system ; diseases of its 
substance. 
Systematic lesions of iSSTHESODic system. 
(1) Sclerosis of columns of Goll, 

(£) Sclerosis of columns of Burdach (locomotor ataxia). 
Systematic lesions of kinesodic system. 
(1) Sclerosis of columns of Tarch, 

(£) Sclerosis of lateral columns (sposmodic tabes, tetanoid pa- 
ralysis, spastic spinal paralysii*). 
(5) Amyotrophic lateral sclerosis of the cord, 
(Jt) Myelitis of the anterior horns of the gray matter (atrophic 
spinal paralysis). 

(5) Polio-myelitis. 

Acute variety; infantile spinal paralysis; non-febrile 
variety ; chronic variety. 

(6) Progressive muscular atrophy. 

(7) Central myelitis. 

Non-systematic or "focal" lesions of the cord. 

Distinctions between systematic and focal lesions; their physi- 
ological effects at different heights. 
(/) Focal lesions of the upper cervical region. 

Symptoms referable to the phrenic nerve ; t(i the respira- 



XX TABLE OF CONTENTS. 



tory center; to the acceleratory center of the heart; 
to the pneumogastric nerve. 

{2) Focal tenons of the certieal enlargement. 

Symptoms referable to cilio-spinul center ; to the ulnar 
nerve ; to the acx^eleratory center of the heart ; to the 
▼aso- motor centers. 

(J) Foeal lesions of the mid-dorsal region. 

Symptoms referable to the lower limbs; to the genito- 
urinary organs ; to the reflex excitability of the spinal 
cord ; to the lateral columns of the spinal cord ; to 
the rectum. 

{Jf) Foeal lesions above the lumbar enlargement. 

Symptoms referable to reflex excitability of the spi- 
nal cord; to the genito-urinary organs; to the rec- 
tum. 

(5) Focal lesions of the lumbar enlargement of the spinal cord. 

Symptoms referable to the sciatic nerve; to the rec- 
tum. 

(6) Focal lesions of one lateral half of the spinal cord. 

(a) Spinal hemiplegia — symptoms referable to the inter- 
costal nerves ; to the upper extremity ; to the lower 
extremity ; to the cilio-spinal center ; to the vaso- 
motor centers. 

(b) Uemi-paraplegia— symptoms referable to the trunk ; 
to "trophic" centers; to increased excitability of the 
spinal cord ; to the lower limbs. 



PART IV. 

THE SPINAL NERVES ..... 639-772 

Their subdivisions and points op escape. 
The ooNSTRUcnoN and belative size of their roots. 
The lbnoth and incunation of tiif.ir boots. 
General axioms of nerve distribution. 
The upper cervical nerves .... 648-663 
Table of their branches of distribution ; the cervical plexus — 
its situation, formation, superficial branches, deep bnmches, 
and communications with other nerves. 7 he commnnieans 
noni nerve: its origin and distribution. T/ie phrenic nerve: 
its origin, course, surgical relations, and physiological 
function. Clinical points pertaining to the upper cervical 
nerves: cervico-occipital neuraltna; diaphragmatic neural- 
gia; clonic diaphragmatic spasm (hiccough) ; tonic dia- 
phragmatic spasm (diaphragmatic tetanus) ; and diaphrag- 
matic paralysis. 
The lower cervical nerves .... 663-705 
Table of their branches of distribution. The brachial plexus: 
its situation; its formation and abnormalities; its supra- 



TABLE OF CONTENTS. 



XXI 



The 



clavicular branches ; itB inf ra-clavicnlar branches ; its sar^- 
oal relations ; its communications with other nerves. Nerves 
of the upper extremity ; table of the branches of the outer 
cord of the brachial plexus; table of the branches of the in- 
ner cord of the brachial plexus ; table of the branches of the 
posterior cord of the brachial plexus. The anterior thoracic 
nerves: their distribution ; their clinical aspects. The exter- 
nal or mueeulo-cutancous nerve : its course and distribution 
to muscles ; its cutaneous distribution ; its relation to the 
" bent arm ^' after venesection. Clinical points afforded by 
it: paralysis and its symptoms; anaesthesia of forearm. 
The median nerve: its origin, course, and distribution; its 
surgical relations; its cutaneous distribution. Clinical 
points afforded by it: median paralysis and its symptoms; 
anffisthesia and its variations. The internal and Ueeer in- 
temal cutaneous nerves: their origin, course, and distribu- 
tion ; relations to the intercosto-humeral nerve. The ulnar 
nerve : its origin, course, and distribution ; its surgical rela- 
tions; its cutaneous distribution. Clinical points afforded 
by it : ulnar paralysis, its causes and symptoms ; its relation 
to the surgery of the elbow-joint. The subscapular nerves : 
their origin, course, and distiibution ; their surgical relations; 
their cutaneous distribution. Clinical points afforded by 
them : scapular paralysis. The eircumjfcx nerte : its origin, 
course, and distribution ; its surgical relations ; its cutaneous 
and articular branches. Clinical points afforded by it : cir- 
cumflex paralysis; deltoid atrophy. The museulo-spiral 
nerve: its origin, course, and distribution. Its terminal 
branches (the radial and interosseous nerves) : their distri- 
bution to muscles; their cutaneous distribution. Clinical 
points afforded by it : surgical importnnce of its peculiar 
course ; its relation to traumatic paralysis ; rheumatic affec- 
tions of the nerve. Lead -paralysis : theories as to its etiol- 
ogy; its symptoms; its differential diagnosis; it8 duration. 

DORSAL NERVES ..... 

The thoracic intercostal nerves ; the thoracieo-abdaminal in- 
tercostal nerves: their origin, course, and distribution ; their 
relation to the pleura. Clinical points afforded by them : 
significance and diagnostic value of thoracic pain ; signifi- 
cance of pain in the pit of the stomach ; significance of pec- 
toral pain ; significance and course of pain d'le to the liver 
and other viscera. Intercostal neuralgia: its causes; its 
symptoms ; its differential diagnosis. Neuralgia of the mam- 
mary gland (roastodynia) : its causes and symptoms; its 
** puncta dolorosa.*' Paralysis* of the dorsal nerves : its re- 
lations to kyphosis; its relations to scoliosis. Paralysis of 
the extensor mnscles of the lumbar region: its diagnosUo 
attitude; its differential diagnosis. 



705-722 



xxii TABLE OF CONTENTS. 



p. 



The lumbab nebves ..... 72^743 

The lumbar plexus: its sitoatioD and formation; its chief 
branches and their general distribution. The ilio^hypo- 
gcLStric nerve: its origin, coarse, and distribution; neuralgia 
of the nerve. The ilio-inguinal nerve: its origin, coarse, 
and distribation ; neuralgia of the nerve ; its relation to the 
peritoneum. The external cutaneous nerve : its origin, coarse, . 

and distribution ; its relation to pains referred to the thigh. 
The genitih-erural nerve : its origin, coars>e, and distribation. 
Clinical points afforded by it. The anterior crural nerve: 
its origin, course, and distribation ; its physiological fane- 
tions; its distribation to joints: its cutaneous branches. 
Clinical points afforded by it : its surgical relations ; its rela- 
tion to pain in the region of the knee. Spasm of the quad- 
riceps extensor muscle. Crural paralysis: its causes and 
Symptoms. Atrophy of muscles supplied by tliis nerve. 
Crural neuralgia: its causes; its^^puncta dolorosa^*; the 
*^ spasmodic contracture of Stromeyer.-' The obturator 
nerve : its origin, course, and distribution ; its distribution 
to joints ; its relation to pain in the vicinity of the knee ; its 
physiological functions. Clinical points afforded by it: 
obturator neuralgia: obturator paralysis. The acceesory 
obturator nerve : its origin, course, and distribution ; its ab- 
normalities. 

The 8ACBAL NEBVES ..... 743-772 

Their anatomical peculiarities. The sacral plexus : its shape 
and formation ; its situation ; its branches of distribution. 
The superior gluteal nerte : its origin, coarse, and distribu- 
tion ; its physiological function. Clinical points afforded by 
it: peculiarities of its cutaneous distribution; its surgical 
relations; gluteal spasm ; gluteal paralysis. The muscular 
branches of the sacral plexus: their distribution; their 
physiological functions. The small sciatic nerve : its origin, 
course, and distribution ; its physiological functions ; rela- 
tion of its perineal branch to the genital organs. Thepudic 
nerve: its origin, course, and distribution; the inferior 
hsemorrhoidal nerve ; the perineal nerve ; the dorsal nerve 
of the penis. Clinical points afforded by the pudic nerve : 
its relations to coitus ; its relations to micturition ; its rela- 
tions to defecation ; neuralgic affection of its branches. 
The great sciatic nerte : its origin, course, and distribution ; 
its distribution to joints. The external popliteal nerve: its 
coarse and branches of distribation. Distribution of nerves 
to the fascia of the leg. The internal popliteal nerve : its 
course and branches of distribution. Clinical points afforded 
by the great sciatic nerve and its branches. Sciatic neuralgia 
(malum Cotunnii) ; its causes; modifications of its seat ; its 
characteristic symptoms ; its " puncta dolorosa '' ; its motor 



TABLE OF CONTENTS. xxiii 



manif estatioDs ; its vaso-motor effects. Spasms of the lower 
limb : spasmodic contraction of the hip ; tonic and clonic 
spasms of extensor and adductor groups of muscles ; spasm 
of the anterior muscles of the leg. Paralysis of the great 
sciatic nerve or its branches: sciatic paralysis; peroneal 
paralysis; tibial paralysis; their sensory manifestations; 
their trophic disturbances. 
INDEX 772-791 



LIST OF ILLUSTRATIONS. 



1. NeBYB FIBBB8 FBOM THE HITMAN 8UBJE0T . 

2. Cebyioal and thobaoio pobtion of the 

8ympathsti0 ..... 
8. lumbab and 8a0bal pobtion8 of the stm- 

PATHBTIO ..... 

4. FiBBBS OF ReMAK .... 

5. Mode of tebmination of the motob 

NEBYE8 ..... 

6. Plan in outline of the bbain in pbo- 

FILE ..... 

7. A DIAGBAM OF THE CHIEF COMPONENT PARTS 

OF THE HUMAN BBAIN 

8. A DIAOBAM OF THE GENEBAL ABBANOEMENT 

OF THE FIBEBS OF THE CEBEBB0-8PINAL 
8T8TEM ..... 

9. DlAGBAM OF THE COMMISSURAL FIBEBS OF 

THE ANTEBIOB BEOION OF THE BBAIN 

10. DlAGBAM OF THE C0MMIS8UBAL FIBEBS ON 

THE LEVEL OF THE COBPUS STBIATUM 

11. DlAGBAM TO ILLUSTBATE THE GENEBAL OTTT- 

XINE OF THE CORPUS CALL08UM AND THE 
FOBNIX ..... 

12. Schematic bepbesentation of Metnert^s 

THREE projection SYSTEMS OF NERYE 
FIBERS ..... 

18. Diagrammatic representation of the 

FIBERS in the CEREBBUM . 

14. dlagbam of the coubse of sen80by and 

motob tbacts in the mesocephalon and 
hemi8phebes .... 

15. a diaobam of the bbain in tran8yer8e 

yertical section .... 

16. Stbuctube of the convolutions . 



Kdlliier . 


PAOl 

5 


Sappey 


6 


Bohin . 


8 
11 


Houget. 


12 


Quain . 


28 


Hanney 


24 


Ranney 

(modified from LandoU) 25 


Lvy9 . 


27 


II 


29 



AlUn (modified from) 80 



Ranney 
Le Bon 

Segnin . 

Dalton 
Baillarger 



82 
86 

88 

89 
44 



XXVI 



LIST OF ILLUSTRATIOm. 



no. 

ir. 

18. 



19. 

20. 
21. 
22. 
23. 
24. 
25. 

26. 

27. 

28. 
29. 

80. 

81. 

82. 

88. 

84. 

85. 

86. 



Cortical cell of the deeper zones . Luyn . 

EIalf diagrammatic figure of the cere- 
bral cortex, giving a view of the 
arrangement of the different zones 
OF cells, and their relations to one 
another, and to the surrounding neu- 

ROGUA . . . . . " . 

A TRANSPARENT SECTION FROM A SULCUS OF 
THE third FRONTAL CONVOLUTION OF THE 

HUMAN BRAIN .... Meyutrt 
Lateral view of the human brain, show- 
ing ITS lobes and fissures . . Ferrier 

A DIAGRAM of THE CEREBRUM IN LONGI- 
TUDINAL MEDIAN SECTION . . . BaltOU . 

a diagrammatic figure, showing the 

cerebral convolutions . . . " . 

Orbital surface of the frontal lobe and 

ISLAND OF Reil .... Tumer 

A DIAGRAM OF THE FIBERS OF A LATERAL 

HALF OF THE CEREBRUM . . . Reichart 

Side view of the brain of man and 

THE areas of the CEREBRAL CONVOLU- 
TIONS ..... Ferrier 
Upper view of the brain of man and 

THE situation OF AREAS OF THE CERE- 
BRAL CONVOLUTIONS ..." 
A DIAGRAM ILLUSTRATING THE COURSE OF 

NEKVE IMPULSES IN THE CEREBRUM . Dodds . 

Superior aspect of the encepualon . Eirschfeld 
Convolutions on the internal aspect op 

the cerebral hemispheres . . Sappey 

Outline of skull resting upon the al- 

VEOLO- CONDYLOID PLANE OF BrOCA . Seguiu . 

Antero-posterior vertical section of the 

BIGHT hemisphere .... Dalton . 

A DIAGRAM of THE AFFERENT AND EFFERENT 

FIBERS OF THE CORPUS STRIATUM . . RaUTiey 

View from above of the third ventri- 
cle AND A PART OF THE LATERAL VEN- 
TRICLES ..... Ilenle . 

Section across the optic thalamus and 
corpus striatum in the region of the 

MIDDLE COMMISSURE . . . Schofcr 

Right half of the encephalic peduncle 

AND cerebellum, AS SEEN FROM THE IN- 
SIDE OF A MEDIAN SECTION . . Re'ichart 

A DIAGRAM OF THE NUCLEI OF THE OPTIC 
THALAMUS AND THE CONVERGING FIBERS 
▲S80CIATIN0 WITH THEM . . . Luy» . 



PAflS 

46 



49 

52 
59 
61 
68 
64 
67 

79 

81 

94 
107 

109 

114 

128 

180 

184 

136 
137 
144 



LIST OF ILLUSTRATIONS. 



xxvu 



no. 

87. A DIAOBAM OF THB INNEB SUBFACB OF THB 

OPTIO THALAMUS, ^ITH THB TUBULAB OBAY 
MATTEB BBMOTED; SHOWING THB THIBD 
TBNTBIOLB, AND THE ABBAN6EMBNT OF 
NEIOHBOKIN6 PABT8 

88. A DIAOBAH OF THE BELATIONS OF THE IN- 

TEBNAL CAP8ULB OF THE OEBBBBUM TO AD- 
JAOBNT STBUOTUBES VIEWED FBOM ABOVE . 

89. A DIAGBAM OF THB SUBDIVISIONS OF THB 

INTBBNAL CAPSULE .... 

40. A DIAGBAM OF THB AFFEBENT AND BFFEB- 

ENT FIBEB8 OF THB OOBPUS BTBIATUM 

41. MiLIABY ANEUBTSM8 .... 

42. A DIAGBAM OF THB BELATIONS OF THB OPTIO 

AND OlFAOTOBT NEKYE FIBEB8 TO SUB- 
BOUNDING PABTS .... 

43. A DIAGBAM TO HXUSTBATE THB LATEST VIEWS 

IN BEFBBENOB TO THB OOUBSE OF THE OP- 
TIO FIBEBS ..... 

44. A DIAGBAM OF THE GENEBAL COUBSB OF 

FIBEBS IN THE ^^ SENSOBT " AND *^ MOTOB 
TBAOTS," AND THBIB BBLATION TO OEB- 
TAIN FASOIOULI OF THB OPTIO TBAOTS 

45. A DIAGRAMMATIC BEPBESENTATION OF THB 

PABTS SEEN IN A HORIZONTAL CBOSS-SEC- 
TION ON A LEVEL WITH TUB BUPEBIOB 
QUADBIGBMINAL BODY 

46. A DIAGBAM OF THE COUBSB OF THE FIBERS OF 

THE CRU8TA CEBEBBI (MOTOB) AFTEB THEY 

leave thb pyramids of the medulla . 

47. Cebebellum and meduixa oblongata 

48. a diagram of the vabi0u8 sets of fibebs 

compbised within the gerebbo-spinal 

SYSTEM ..... 

49. A CRUDE DIAGBAM ILLUSTRATING THE THBEE 

PA IBS OF PEDUNCLES OF THE CEBEBELLUM 

50. AnTEBIOB VIEW OF THB MEDULLA OBLONGATA 

51. Anterior view of the medulla and pons, 

designed to show some of thb bela- 
tions of subbounding pabts and thb 
apparent origin of thb cranial nerves 

52. a diagram to show the mors important 

subdivisions of the spinal cobd 
58. a diagbam of a section of the medulla 
at the middle of tub motor decussa- 
TION ..... 
54. A DIAGRAM OF A SECTION OF THE MEDULLA 
AT A SUGHTLY HIGHEB LEVEL THAN IN 
THB PRECEDING FIQUBB 



Baii'My 



Bummond 



Banney 



Banney 

(modified from Seguin) 



Banney 



nir9c1{feld 

Banney 

(modified from Bon) 

Banney 
Sappfy 



Banney 
Flechsig 



149 

152 

154 

160 
164 

185 

189 

198 

201 



208 
217 



224 

227 
245 



248 
250 



Banney (after Quain) 251 



252 



xxvni 



LIST OF ILLUSTRATIONS. 



no. 
65. 



56. 
57. 

58. 

59. 

60. 
61. 

62. 

63. 

64. 

65. 
66. 
67. 



68. 
69. 

TO, 
72. 



TSAKSPABENT LATERAL VIEW OF THE MEDUL- 
LA, SHOWING THE RELATIVE POSITIONS OF 
MOST IMPORTANT NUCLEI; RIGHT HALF OF 
THE MEDULLA, SEEN FROM THE SURFAOE OF 
section; THE PARTS THAT LIE CLOSER TO 

this surface are deeper shaded . eth 

Diagram of the chief tracts in the me- 
dulla . . . . . '* . 
A cross-section of the medulla oblon- 
gata on a level with the SUPERFICIAL 

origin of the AUDiTORr NERVE . . FUehdg 

A TRANSVERSE SECTION THROUGH THE PONS, 

ON A LEVEL WITH THE ROOTS OF THE 

SIXTH AND SEVENTH CRANIAL NERVES 

FROM A NINE MONTHS^ EMBBTO . 
A TBANSVEBSE SECTION OF THE MEDULLA 

(PABTLY schematic) MADE THROUGH THE 

MIDDLE OF THE OLIVARY BODY 
The PATHS OF the motor fibers of THE 

CORD ..... 

A DIAGRAM OF THE TWO 8UBDIVI8IOX8, OR 

TRACTS, OF THE ANTERIOR ROOT ZONES OF 

THE SPINAL CORD .... Ranuey 
a diagram of the right lateral half 
op a transverse 8ecti0n of the pons 
Varolii on a level with the origin 

OF THE fifth CRANIAL NERVE 
A DIAGRAM OF THE COURSE OF CERTAIN 
SPECIAL NERVE TRACTS WITHIN TIIF. CERE- 
BRUM, CRrS CEREBRI, PONS VaROIJI, ME- 
DULLA OBLONGATA, AND 8PINAL CORD 
A DIAGRAM OF THE RELATIVE SITUATION AND 
FUNCTIONAL ASSOCIATION OP THE DIRECT 
CEREBELLAR COLUMN OF THE SPINAL CORD, 
AND THE VESICULAR COLUMN OF ClARKE RaUUey 
A DIAGRAM TO ILLUSTRATE THE METHOD OF 

PRODUCTION OF CROSSED PARALYSIS . Hammond 

View from above of the third ventricle 

and a part of the lateral ventricles henu . 
a diagram of the inner surface of the 
optic thalamus, with the tubular gray 
matter removed, showing the third 
ventricle, and the arrangement of 
NEIGHBORING PARTS . . Rannty 

The BASE OF the skull and cranial NERVES ** 

A diagram of the probable decussation 

OF THE FIBERS OF THE OLFACTORY TRACTS " 

71. The visual tracts . . . Mnnh . 

The normal visual field . Eon . 



254 
255 

268 



Ranney (modified from 

Erh and Ross) . 260 

Ranney 

(modified from Spitzka) 262 
Ranney (modified from 
Bramwell) . . 278 



274 



Ranney 

(modified from Erh) . 276 



Ranney (modified from 
FUchsig) . . 280 



281 
292 
809 



812 
330 

882 
833 
885 



LIST OF ILLUSTRATIONS. 



XXIX 



78. Horizontal section of ▲ monkey^b bbaik 

74. a oiaobam of the obioin and c0ub8b of 

thb fourth cbanial nebvb 

75. Section of the medulla at its upper pabt 

76. Roots of the cbanial nebtes 

77. Olfactory ganglion and nertes 

78. Terminal filaments of the olfactory 

nerve ..... 

79. Internal branches of the olfactory 

NERVE ..... 

80. Optic tracts, commissube, and nebves . 

81. a diagbam of the decussation of the 

optic f1beb8 .... 

82. a diagram of the optic fibebs in the 

BBTINA ..... 

83. Relation of the optic nerve and oph- 

thai^ic abteby .... 

84. Relation of the optic nebvb to the 

blood-vessels, in the orbit 
86. a diagram of thb defective diameters 
of the eye .... 

86. Anterior view of the crystalline lens 

87. two cuts of the retina and its ele- 

MENTS . 

88. A DIAGRAM TO SHOW THE LIMITS OF COLOR 

VISION ..... 

89. Lachrymal and Meibomian glands 

90. Lachbymal appabatus 

91. a dl40bam to show thb effects of press- 

ure on the optic nerve 

92. Distribution of the third cranial nerve 
98. The ciliary muscle* lens, iris, and cornea 

94. The ciuary nerves and choroid coat of 

EYE ..... 

95. The nerves of the iris 

96. The ciliary nerves 

97. a diagram showing the mechanism of 

the accommodation of vision . 

98. Muscles of the eyeball . 

99. a diagbam showing the axes of bota- 

tion of the eyeball 

100. two diagbams of the elements of the 

RETINA ..... 

101. Distribution of the fourth chanial 

NERVE ..... 

102. The ophthalmic division of the fifth 

cranial nerve .... 
108. A diagram of the distribution of the 

fifth CRANL4L NEBVB 



Wernicke 

Ranney 
Quain . 
Uirechfeld, 



KdlUker 

Sappey 
HirtcJ^eld 

Flint . 

Weber . 

Ranney 



Babuehin 

Mailer and Sappey 



Hirechberg 
Sappey 



Ranney 

Eincl^eld 

Sappey 



Fiei . 
Sappey 



Fieh . 

Mailer and Sappey 

Ilirtchfeld 



Flomer (modified from) 



PAOS 

887 

888 
889 
842 
848 

848 

845 
850 

851 

852 

854 

854 

856 
862 

868 

865 
867 
868 

871 
874 
875 

876 
877 
879 

880 



885 
890 
896 
898 
400 



XXX 



LIST OF ILLUSTRATIONS. 



Ml4, TlIK INFICRIOn MAXILLAKY DIVISION OP THE 

rimi CRANIAL NRRVR . HirKhfeld 

lO/J. TllR MIJt'KRIOR MAXILLARY DIVISION OF THE 

rtrrii cranial nrrvr . . . ^^ 

100, HrfKicriouL nRANciiRis of the fifth and 

rAOIAL NKKVKH . . . . ^^ 

107, (/ftTAMK/Mm NKRVB DIHTRIBUTION OF THE 

ffKAii ..... Flower 

lOH, HlMTUffltrrfON OK TllR HIXTH CRANIAL NERVE ffirsch/cld 
Ul^, TttK MIM'KKtrM.'IAL HRANi HKH OF THE FACIAL 

nKttVK .....** 

110, A DfAOMAM OK TlIK IIRANCHEH OF THE 

KAr?iAL NRRVR .... Riinncy 

111. Kxf'RKMlON OK TlIK KAC^R IN " BeLL's PA- 

RA LYMIM^^ ..... Corfe . 
\\*l, A tilAHHAM OK TlIK (M»MMUNI0ATI0N8 BE- 
tWKRN TlIK FACIAL AND TRIOEMINUS 

WKRVRM , . . . . Ranney 

\\^. TmK CIMlRDA TYMI'ANI NKUVK . . IHrSch/eld 

l\i, A DUORAM OK TlIK < oirRMK OV TlIK VIDIAN 

A«D I'KTROMAL NKRVFH . . . Ranncy 

115, A DUORAM OK TlIK AI IUT«»HY NKRVK AND 

tin Mir AN* lll'.M ....** 

\\(S, \h*^tunut\iri itv 'I Ml: cociiii'iAR nkhvk . Sitppcy 

117, (iKNKRAL VIKW Ol' IIIK oh«*aN OK IIKAKIN'O '* 

IIH. A DIAORAM lO II 1.1 MlllATK ttlK MK<'IIAMHM 

OK MKAKiNo .... Ranney 

in>, TmK. OJtMICLKH Ol' TIM'. TYMI'AM M . . ArUoJd 

120. TlIK liONV LAiivifiMii OK A M'.w HORN' riiiM) Rudr'uigcr 

121. A DIAORAM OK IIIK lAliyKINTII, VKHTIIirii:, 

AND MKMKJIIini.AIt rAVAl.rt . ** 

122. A DIAORAM OK IIIK r<H|||j:A ON TKANHVKRHK 

HKCTioN ..... Ratitiry 

123. A VERTICAL HKCTION OK TlIK '*OUOAN OK 

(JoRTi " . . . . . WaUnjer 

124. The two imli.aum ok tiik *'ouoan ok 

('oirri '* . . . . . «SV/;7>ry 

125. I)ihtrihi:tion ok tiik <:o<:ni.KAit nkhvkh . 

126. Memhrana tymi'ANI, hkkn kuom within . liudrlnger 

127. Section ok tiik cociilka ok tiik cat and 

HUMAN FfETI'S . . . . " 

128. The glohho-pharynoeal nkrvk . . Stippey 

120. A diagram of the OLOSrtO-I'IIAIiYNdEAL 

nerve ..... Ranney 

180. Tiik papill.b of the tonoce . . Suppey 

181. a circrmvallate papilla ..." 
132. The fungiform and fiuform papill.e . " 

188. The taste-bcds .... Engelmann 
134. The oavities of the mouth and pharynx Sappey 



FA«X 

401 

402 

403 

405 
422 

424 

425 

427 

429 
431 

482 

444 
445 
446 

448 
449 
450 

451 

452 

453 

454 
455 
458 

460 
468 

468 
469 
470 
470 
472 
474 



LIST OF ILLUSTRATIONS. 



XXXI 



186. ThB MT780LE8 OF THE PHABYNZ . . Sappey 

186. Anastomoses of the pneumooastbio kebvb Hir^e^feld 

187. A DIAGBAM OF THE OBBVIOAL POBTION OF 

THB PNBUMOOA8TEIO NBBYB . . Bantiey 

188. A DIAGBAM OF THE TBOBAOIO AND ABDOMI- 

NAL POBTIONS OF THB PNEUMOOASTBIO 
NBBYB ..... 

189. DlSTBIBUTION OF THE PNEUMOOASTBIO NEBVB 

140. NeBVES of the LABTNX, POSTEBIOB VIEW . 

141. Nebves of the LABTNX, latebal tiew . 

142. Bbanohes of the pxeumogastbio kebyb 

to the heabt .... 
148. The spinal aooessobt nebyb 
144. postebiob yiew of thb mu80le8 of the 

LABYNX ..... 

146. Latebal yiew of the muscles of the 

LABYNX ..... 

146. A DIAGBAM OF TUB SPINAL ACCESSORY 

NEBYE ..... 

147. The glottis, as seen with the laryngo- 

scope DUBINO THB EMISSION OF HIGH- 
pitched sounds .... 

148. The spinal accessoby nebye 

149. dlstbibution of the hypoglossal nebye 

160. Anastomotic loop formed by the de- 

scending BBANCH of THB HYPOGLOSSAL 

nerye and the intebnal descending 
br*ancn of the cebyical plexus 

161. a diagbam of tho hypoglossal nebye 

and its branches 

162. Glosso-labio-laryngeal paralysis 
168. Glosso-labio-labtngeal pabalysis 
164. a diagbam of thb motob points of the 

face, showing the position of thb 
electbodes during electrization of 
special muscles and neryes . 

166. CbRYIOAL POBTION OF THB SPINAL COBD . 

166. DOBSAL POBTION OF THE SPINAL COBD . " 

167. InFEBIOR POBTION OF THE SPINAL COBD 

AND CAUDA EQUINA . . . ^^ 

168. TbANSYERSE section of the CERYICAL EN- 

LARGEMENT OF THE SPINAL CORD AT THE 

ORIGIN OF THE FIFTH PAIR OF NERYES . Stilling 

169. Trans YEBSB section of the spinal cobd 

OF A CHILD SIX MONTHS OLD . . .Gerlaoh 

160. DiAGBAM OF THE ARBANGEMKNT OF THE 
DIFFEBENT MEMBRANES AND SPACES AS 
THEY ARE BELIEYED TO EXIST IN THE 
BPINAL COLUMN .... EilUm 



PAOB 

476 
483 

484 



it 

HirKhfeld \ 

Sappey 

tt 


. 487 
. 488 
. 490 
. 490 


Bernard 
Birtelifeld . 


. 491 
. 606 


Sappey 


. 607 


ti 


. 607 


Ranney 


. 608 


LeBon 

Sappey 
it 


. 609 
. 611 
. 619 



Hinchfeld 

Ranney 
Hammond 



Ziemseen (modified 
from) . 
Eirseh/eld 



620 

621 
624 
626 



628 
634 
634 

684 



636 
688 

640 



xxxu 



LIST OF ILLUSTRATIONS. 



no. 

161. A DIAGRAM DESIGNED TO SUOW THE BELA- 

TI0N8 OF THE YERTBBBiB TO THE SPINAL 
SEGMENTS, AND OF THE SPINAL NEBYES TO 
THE MOTOB, SBNSOBT, AND BEFLEX FUNO- 
TIONS OF THE SPINAL COBD . . GoweTB 

162. SeMI-DIAGBAMMATIO TBANSYEBSE SECTION OF 

THE GBAT SUBSTANCE OF THE CEBYICAL 
AND LUMBAB ENLABGEMENTS OF THE SPI- 
NAL COBD . . . . . Frb 
168. A PIECE OF THE WHITE SUBSTANCE OF THE 
SPINAL COBD, AS SEEN ON A TBANSYEBSE 
SECTION . . . . . " . 

164. Section of the cobd below the medulla 

oblongata .... 

165. Section of the cebyical enijlboement 

of the cobd .... 

166. Section fbom the dobsal begion of the 

COBD ..... 

167. Section of the lumbab enlabgement of 

the COBD ..... 

168. DiAuBAM illustbating the belations of 

THE NEBYE-FIBEB TRACTS IN THE SPINAL 
COBD ..... 

169. A DIAGBAM OF THE ABBAS OF THE DIBECT 

AND CBOSSED PYBAMIDAL TBACTS IN A 
SECTION OF THE SPINAL COBD, AND THE 

FiBEBS THAT COMPOSE EACH . Rauney 

170. A DIAGBAM ILLUSTBATING THE DEYELOPMENT 

OF THE DIFFEBBNT SYSTEMS OF FIBEBS IN 

THE SPINAL COBD .... FUchdg 

171. Diagram of a transverse section of 

SPINAL cord in upper HALF OF DOBSAL 
BEOION ....." 

172. DiAGBAM OF A SPINAL SEGMENT TO SHOW 

ITS COMPONENT PABTS . . Rantiey 

178. A DIAGBAM TO ILLUSTBATE THE CIBCLE 
OF REFLEX ACTION IN A SPINAL SEG- 
MENT ..... 

174. A DIAGRAM OP THE PATHS OF MOTOR AND 

SENSORY CONDUCTION IN THE SPINAL 
COBD ..... 

175. A DIAGRAM OF THE CONNECTIONS OF THE 

MOTOR AND SENSORY CONDUCTING TRACTS 
WITH THE SPINAL NERYES 

176. A DIAGRAM OF THE VARIOUS PATHS OF SEN- 

SORY CONDUCTION IN THE CORD . . Ranncy 

177. Multipolar nerve cell from the ante- 

rior CORNU OF THE SPINAL CORD OF 

THB OX . . . . . Deiters 



546 



558 



"... 554 

Sappey . . 555 

" . . 555 

" . . 556 

" . . 566 

Ranney (modified from 

FUchsig) . . Plate 



559 

564 

565 
567 



Ranney (modified from 
Bramwelf) . . 567 

Ranney (modified from 
Bramwell) . . 569 

Ranney (modified from 
Bramwell) . . 571 



572 



581 



LIST OF ILLUSTRATIONS. 



XXXIU 



no. 

178. Tbanbykbsb sbotion of the obat sub- 

stai^ob of thb aktebior oobnua of 
thb spinal oobd of the ox, tbbatbd 

Wrm NITBATB OF SILYBB . 

179. A DIAOBAH OF THB C0UB8B OF THE FIBBB8 

^HIOH OOMPOBE THE SPINAL OOBD 

180. NbBVE cell FBOM the PERBUOINOnS BUB- 

8TAN0E ^HICH FOBMS TUB FLOOB OF THE 
BHOMBOIDAL SINUS IN MAN 

181. A DIAOBAM TO SHOW THE DEOUBBATION OF 

MOTOB NEBVE FIBBB8 IN THB MEDULLA 

oblongata .... 

182. Atbophio spinal pabaltbis with OON- 

TBACTUBE . . 

188. Pboobesbiyb musoulab atbophy of the 
uppeb bxtbem1tt. 

184. Pboobbbsiyb musoulab atbopht. Aob of 

PATIENT, FOBTY-FIYE YEABB 

185. A DIAOBAM BHOWINO THB RELATION OF THE 

SPINOUS PB00E88BB OF THE YEBTBBBJE TO 
THE SPINAL NEBYE8 AND SPINAL OOBD . 

186. A DIAOBAM TO SHOW THE C0UB8E OF THE 

MOTOB AND BBNSOBT PATHS IN THE SPI- 
NAL COBD. .... 

187. a diaobam to show thb belation of the 

spinous pb00es8eb of the yebtebba to 
spinal nbbyes .... 

188. The oebyioal pobtion of the spinal cobd 

189. The dobsal portion of the spinal oobd 

190. Tub infebiob pobtion of the spinal cobd 

and oauda equina 

191. postebiob bbanch of the second oebyi- 

oal nebye .... 

192. supebficial bbancubb of thb oebyioal 

PLEXUS ..... 

198. The nbbyb supply of the postbbiob pabt 

OF THB head .... 

194. The nebye supply of the postbbiob pob- 

tion OF the head and neck 

195. A DIAOBAM OF THB BBAOHLAL PLEXUS AND 

its bbancues .... 

196. Antbbior branoiies of the foub last 

cebyical and fibst dobsal nbbyes 

197. Collateral bbanohes of the bbachial 

PLEXUS ..... 

198. Bbachial pobtion of the musculo-cuta- 

neoum, median, and ulnab neryes 

199. Cutaneous nerves of the anterior sur- 

face OF THE forearm AND HAND 
8 



Orandry 
Banney 

KdlUher 

Fleehiig and Seguin 
Hammond 

a 

Friedreich 



Brown- SSquard 



588 

585 

586 

618 
619 
621 
622 



Malgaigne and Seguin 626 



635 



Malgaigne and Seg 
Hirtchfeld . 


titn 686 
. 642 
. 642 


ti 


. 642 


Arnold 


649 


Hir9chfM 


651 


HiUon. 


652 


Flower 


. 658 


Gray . 


665 


HirechftU . 


. 666 


a 


. 667 


Sappey 


. 672 


Hirto^feld 


. 675 



XXXIV 



LIST OF ILLUSTRATIONS. 



200. Cutaneous nebybs of the shoulder and 

p08tbri0b surface of the arm. 

201. Cutaneous nerves of the posterior sur- 

face OF the forearm and hand 

202. Brachial portion of the musculo-cuta- 

NEOUS, median, and ULNAR NERVES 

208. Terminal portion of the median and 
ulnar nerves .... 

204. Diagram of the regions of the cutane- 

ous NERVE distribution ON THE ANTE- 
RIOR SURFACE OF THE UPPER EXTREMITY 

and trunk .... 

205. The cutaneous nerves of the shoulder 

and anterior surface of the arm 

206. The cutaneous nerves of the anterior 

surface of the forearm and hand 

207. Brachial portion of the musculo-cuta- 

NEOUS, median, and ULNAR NERVES 

208. Terminal portion of the median and 

ulnar nerves .... 

209. The circumflex and subscapular nerves 

210. The musculo-spiral nerve 

211. The terminal branches of the musculo- 

spiral nerve .... 

212. a diagram of the regions of cutaneous 

nerve DISTRIBUTION ON THE POSTERIOR 
SURFACE OF THE UPPER EXTREMITY AND 
TRUNK ..... 

218. The motor points on the outer aspect 
of the arm .... 

214. The motor points on the inner side of 

THE ARM ..... 

215. The motor points on the extensor (pos- 

terior) ASPECT of the forearm 

216. The motor points on the flexor (ante- 

rior) ASPECT of the forearm . 

217. The intercostal nerves 

218. The nerves situated on the posterior 

part of the trunk 

219. a diagram of the regions of cutaneous 

nerve distribution in the anterior 
surface of the upper extremity and 

TRUNK ..... 

220. A DIAGRAM OF THE REGIONS OF CUTANEOUS 

NERVE DISTRIBUTION ON THE POSTERIOR 
SURFACE OF THE UPPER EXTREMITY AND 
TRUNK ..... 

221. The lumbar plexus 

222. The outanbous nerves on the thigh 



Sappey 



Flower 
Hirse^feld 

Sappey 



Flower (modified from) 



Ziemssen 



Masse 



677 
678 
680 
680 

682 

685 

685 

687 

687 
693 
695 

695 

697 
701 
702 
708 

704 

707 

709 



Flower (modified from) 711 



(i a II 

IIirsef{fcld 



716 
721 
728 



LIST OF ILLUSTRATIONS. 



XXXV 



228. The muboulab bbanohbs of thb antbbiob 
and intebnal pobtionb of the thigh . 

224. a diaobam of the outaneoub bupplt 

of the antebiob abpect of the loweb 
extbemity .... 

225. cutaneoub nebyb8 of the antebiob pabt 

of the thioh .... 

226. dlagbam of the gt7taneotjb bupply of 

thb pobtebiob abpect of thb loweb 
extbemitie8 .... 

227. Muboulab bbanoheb of the antebiob and 

intebnal pobtionb of the thioh 

228. The bmall boiatio nebte with itb bbanoh- 

eb OF DIBTBIBUTION AND TEBMINATION . 

229. The obeat bciatio nebye with itb bbanoh- 

eb OF DIBTBIBUTION AND TEBMINATION 

280. Tub extebnal popliteal nebye . 

231. The intebnal poputeal nebye 

282. The extebnal baphenoub nebye and its 

acoebboby, the comiunioanb pebonei . 
238. The plantab nebyeb, theib ooubbb, anab- 

tomobeb, and dibtbibution 

284. The deep bbanoh of the extebnal plan- 

tab NEBYE .... 

285. The motob pointb on the pobtebiob ab- 

peot of thb thioh 

286. The motob pointb on the antebiob ab- 

peot of the thigh 

287. The motob pointb on the inneb abpeot 

OF the leg .... 

288. The motob pointb on the outeb abpeot 

OF the LEO .... 



Sappey 

Flower (modified from) 
Sappey 



PAOB 

781 



785 



Flower (modified from) 


787 


Sappey 


• 


789 


(I 




761 






756 
757 


(i 


• 


769 




• 


761 
762 


11 


• 


768 


Zienuaen (mod. from) 


766 


ii (( 


(( 


768 


ti ti 


(( 


770 


U ti 


ti 


772 



GEIOJRAL INTRODUCTION. 

THE NERVOUS SYSTEM CONSIDERED AS A WHOLE, AND 
THE AXIOMS OF NERVE DISTRIBUTION. 



GENERAL INTRODUOTIOK 



Gentlemen: The subject of the nervous system, which 
has been chosen as the theme of my winter's course of lect- 
ures, is one which probably comprises more points of prac- 
tical interest than any other portion of anatomy. I say of 
practical interest, because there is hardly a field of medicine 
or of surgery where the nervous system does not help to 
explain many of the symptoms which might otherwise tend 
to i)ossibly mislead the practitioner, and where it does not 
also afford invaluable aid in the diagnosis of obscure affec- 
tions which might remain unrecognized, without a knowledge 
of the nerves and of their distribution and function, till the 
opi)ortunity of relief to the patient has passed. 

The distribution of those small nerve-filaments which sup- 
ply the skin of the body with sensation, and thus allow of the 
perception of external impressions, such as those of heat, cold, 
pain, and touch, possesses to-day an imi)ortance which is not 
confined to the researches of the physiologist, but which the 
advanced physician and surgeon are both keenly alive to 
grasp in all its practical detail. 

In every work now published upon diseases of the nervous 
system, you will find cuts, which, in less modem treatises, 
have no analogue. These are designed to show the situation 
of certain Tnotor points on the cutaneous surface of the dif- 
ferent anatomical regions of the body, where the electric 
current can be best applied to accomplish certain desired 
effects, and aiso the area of cutaneous distribution of each of 
the sensory nerves. 



4 GENERAL INTRODUCTION. 

The important relationship which exists between the 
nerves of the skin, the muscles underneath it, and the joints 
which those muscles move, is affording the enlightened physi- 
cian a means of tracing the seat of obscure affections, by the 
use of certain general rules governing the nerve-snpply of 
the body, with a degree of accuracy and ease which strikes 
those not famUiar with the method as remarkable. 

The investigations of Meynert,* Turck,* Charcot,* Fenier,* 
Brown-Sequard,* Clarke,' Flechsig,' Luys,' Broca,* Bouillaud," 
Andral," and a host of others, have awakened the profession 
to the fact that many of the old ideas of the anatomy and 
physiology of the brain and the spinal cord were radically 
wrong. By symptoms referable to certain anatomical regions, 
the existence of disease in certain corresponding parts of the 
brain or spinal cord may now be positively localized daring 
life. To what extent this new guide to diagnosis, given us 
by means of investigations calculated to determine the pre- 
cise distribution of the nervous system, may be developed in 
the future, time alone will show. We have, however, ample 
proof that some positive information of a practical character 
has been gained, and that a great advance has been made 
toward accurate knowledge of the anatomy of the nervous 
centers. 

When we consider that every act which distinguishes the 
animated being from the corpses is dependent upon the influ- 
ence of the nerves, and tliat, without these electric wires, the 
heart would cease to throb, the lungs no longer perform their 

» " The Brain of MammalB," " Strieker's Histology," New York, 1872. 

• A paper originally read before the Aeadomy of Vienna in 1851. 

* " Localizations dans les maladies c6rebralos." 

* " Jb'unctions of the Brain " ; *' Localization of Cerebral Disease/* 

»" Lectures on the Physiological Pathology of the Brain," "Lancet," 1876-'77. 

• " Researches on the Intimate Structure of the Brain," " PhiL Trans.," London, 
1858 and 18A8. 

^ " Die Leitungsbahncn im (lehim und Riickenmark dc8 Menschen." 

* " Functions of the Brain," New York, 1882. 

• " Bull, de la Soc. Anat.," 1801. 

10 ** Recherches exp6rimentalc8 sur les fonctions du oenreau." ** Jour, do Phyaiolo- 
gie," Paris, 1830. "Trait6 de TEncdphalite," Parlfl, 1826. 
" *< Clinique H^dlcale." 



GENERAL INTRODUCTION. 6 

function, the eye no longer be capable of vision, the ear no 
longer perceive sound, and that smell, taste, expression, and 
movement would cease to exist, we can then understand how 
much of physiological interest must center around this special 
study, and how necessary is the thorough understanding of 
the distribution and function of the individual nerves, if we 
ever hope to attain a comprehensive grasp of the general plan 
of our construction. 

During the last session, I closed my course of lectures with 
a description of the general construction of nerves and the 
anatomy of the human brain. It wiU assist us, in our study 
of the distribution and practical utility of the separate nerves 
of the body, to hastily review the main classifications of 
nerves and the general plan upon which the nervous system 
is formed. 

The nervous system of the human race consists of the fol- 
lowing component i)arts : 

{The cerebro-spinal axis. 
The motor nerves. 
The sensory nerves. 
2d. The sympathetic nerve and its vaso-motor connections. 
3d. Various ganglia, connected with special nerves. 




Fio. 1. — NnvtjSbenfnm, the human Byhjtet ; magnified 860 diamden, (Kdlliker.) 

Four small fibers, of which two are varicose, one medium-sized fiber with borders of single 
contour, and four large fibers ; of the latter, two ha?o a double contour and two con- 
tain granular matter. 



GENERAL INTRODUCTION. \ 

fifth ; 12, sphmo-pakUine ganglion ; 18, otic ganglion ; 14, lingual branch of the fifth 
nerve; 16, tulnnaxillary ganglion; 16, 17, superior laryngeal nerve; 18, external 
laryngeal nerve; 19, 20, recurrent laryngeal nerve; 21, 22, 28, anterior branches of 
the upper four eervieal nerves^ sending filaments to the superior eervieal sympathetic 
ganglion ; 24, anterior branches of the fifth and sixth cervical nerve sending fuaments 
to the middle cervical ganglion ; 25, 26, anterior branches of the seventh and eighth 
cervical and thefird dorsal nerves^ sending filaments to the inferior cervical ganglion ; 
27. middle eervieal ganglion ; 28, eord connecting the two ganglia ; 29, inferior cervi' 
eat ganglion; 80, Zl^juaments connecting this with the middle ganglion ; 82, superior 
cardiac nerve ; 88, middle cardiac nerve ; 84, inferior cardiac nerve ; 86, 86, cardiac 
plexus ; 36, ganglion of the cardiac plexus ; 87, nerve following the right coronary 
artery ; 88, 88, intercokal nerves with their two fdamenis of communication with the 
thoracic ganglia; 89, 40, 41, great splanchnic nerve; 42, lesser splanchnic nerve ; 
43, 43, solar plexus ; 44, left pneumogastric ; 46, right pneumogastric ; 46, lower end 
of the phrenic nerve ; 47, section of the right bronchus ; 48, arch of the aorta ; 49, 
right auricle; 50, right ventricle; 61, 52, pulmonary artery; 58, right half of the 
stomach ; 54, section of the diaphragm. 

The CEREBRO-spiNAL SYSTEM iiicludes, as its first com- 
ponent part, those nerve-centers inclosed within the cavities 
of the cranium and spinal column, viz., the cerebrum, cerebel- 
lum, cms, pons Varolii, medulla oblongata, and spinal cord. 

The second component part of the system, viz., the motor 
nerves, are efferent nerveSy which carry the impulses of the 
nerve-centers to the muscles. 

The third component part, the sensory nerves, are affefrent 
TierveSy which carry only sensory impressions from the pe- 
riphery of the body to the nerve-centers, viz., to the brain or 
spinal cord. 

The cerebro-spinal nerves are usually found in company 
with the larger blood-vessels. They are protected from injury 
either by investing muscular layers, or, when near the sur- 
face, by the lines of flexion of the joints. 

It is worthy of remark that the foramina of exit of the 
cranial nerves from the base of the skull are less liable to 
variation than those for the transmission of blood-vessels. 

The SYMPATHETIC NERVE * comprfses a continuous chain of 
nerve-fibers and ganglionic enlargements, which extends from 
the head to the coccyx, on both sides of the spinal column, 
and which is in constant communication along it^ course 
with branches of the cerebro-spinal system of nerves. It sup- 
plies branches to various ganglia of the thorax and abdomen, 
and helps to form plexuses of nerves which ramify upon 

> See Fig. 2 and Fig. 8. 



GENERAL INTRODUCTION. 9 

the coats of all the principal blood-vesselSj and which accom- 
pany them throughout the length of their course. It is by 
means of these plexuses upon the blood-vessels that the sym- 
pathetic nerve is enabled to control the involuntary muscular 
fibers within the coats of the blood-vessels, and thus to regu- 
late the vascular supply of the various tissues and organs of 
the body. The nerve-fibers of the sympathetic are therefore 
often called the "nerves of organic life," since they regulate 
the life of tissues by controlling their blood supply ; while 
the cerebro- spinal nerves are contradistinguished as the 
" nerves of animal life," since they control those acts which 
are essential to the life of the individual, such as muscular 
movement, respiration, etc. The frequent communication be- 
tween the sympathetic nerves and those of the cerebro-spinal 
system renders the actions of the two systems in perfect ac- 
cord, and thus supports the universal law of harmony which 
is so beautifully illustrated in all the works of Nature. 

Interspersed along the paths of the motor and sensory 
nerve-tracts, within the substance of the brain and spinal 
cord, special centers connected with sympathetic nerve-fibers 
have been demonstrated— the so-called vaso-Tnotor centers. 

The exact situation and limits of these centers are still a 
matter for future investigation. We know, however, that 
the brain and spinal cord is capable of transforming afferent 
or sensory impulses into efferent vaso-motor impulses, which 
create either constriction or dilatation of blood-vessels. Some 
of the vaso-motor fibers run in the larger nerves of the cere- 
brospinal system. As an illustration of this fact, erection of 
the penis may be artificially produced by stimulation of sen- 
sory surfaces, the blood-vessels of that organ becoming dilated 
to an enormous extent as a result of the sensory impulses 
transmitted to the spinal cord. Exi)eriments of a similar 
character made upon the trunks of cerebro-spinal nerves 
have manifested the effects of stimulation in dilatation of 
blood-vessels of the limbs. 

We know, also, that the brain and spinal cord exercise a 
so-called ^^ trophic a^tion^^ upon the joints, skeletal muscles, 



10 QENEEAL INTRODUCTION. 

and other tissues, governing their nutrition and growth, and 
causing them to respond in the proper way to the demands 
made upon them by the strains and shocks of daily life. 

We are compelled, therefore, to divide the vaso-motor 
nerves into two classes, the vaso-dilator and vaso-canstrictor. 
The former allow of vascular dilatation, and excess of blood 
to the part supplied by the nerve affected or called into action 
is the result of impulses transmitted by these fibers. The 
latter have an opposite action, the vessels being diminished 
in caliber and the blood supply to the part being proportion- 
ately decreased. These nerves will be considered in detail 
later in the course. 

The CEREBRO-spiNAL NERVES comprfse (1) those which 
escape from the foramina of the cranium, called the cranial 
nerves ; and (2) those which are given oflf from the spinal 
cord. The latter escape from the spinal canal by means of 
foramina between the lamina> of the vertebrae, called the 
" inter- vertebral foramina." These are called spinal nerves, 
in contradistinction to the cranial nerves. 

All of the spinal nerves arise by two roots, thus indicating 
that they are provided with both motor and sensory fila- 
ments. The former constitute the anterior and the latter the 
posterior root. 

The cranial nerves are, in some instances, similarly con- 
structed ; having two distinct roots. Others have only one. 
The reason of this anatomical variation is explained by the 
fact that some of the cranial nerves are destitute of motor 
fibers, some of sensory fibers, while others are endowed with 
a special function, such as sight, smell, hearing, and taste. 

Motor-nerve fibers differ from sensory -nerve fibers in re- 
spect to their method of origin and termination. It may be 
stated that motor fibers begin and end in masses of proto- 
plasm (nerve-cells or nerve-plates). Sensory ner^^es appear to 
arise witliin the spinal cord from a net-worJc of fibers, whose 
connections with the sensory cells of the cord are not as yet 
positively determined. They terminate either in a plexus of 
nerve-endings, loops, tactile corpuscles, or in some of the 



GENERAL INTRODUCTION 



11 



apparatuses connected with the si)ecial senses of smell, hear- 
ing, or sight. 

In the course of lectures which I propose to deliver before 
you this winter, it is my intention not only to give the ana- 
tomical origin, course, and distribution of the various nerves, 
but also such points of practical value as 
may be suggested in connection with each ; 
these will aid in remembering the peculiari- 
ties which each presents, and possibly guide 
you often in your practice at the bedside of 
the sick. 

The study of the practical bearing of the 
distribution of the nerves is to-day assum- 
ing an importance in diagnosis which can 
not be over-estimated ; since the physiologi- 
cal phenomena produced by them have a 
direct influence upon the proi)er perform- 
ance of all those functions of the body 
which may be considered as vital to it. 

It is claimed by John Hilton' that, if 
we trace the distribution of the motor nerve 
filaments from any special nerve trunk to 
the muscles, we shall find that only those 
muscles are supplied by each of the indi- 
vidual nerves which are required to render 
the performance of the functions^ for which 
that nerve was designed, complete ; and that, 
if muscles were classified on a basis of their 
nerve supply, instead of in groups of mere relationship as 
to locality, a self-evident physiological relation would be 
shown which would tend greatly to simplify a knowledge of 
the muscular system in its practical bearings, and to prove 
a design on the part of the Creator. 

Thus, he says, we frequently find muscles close together 
and still supplied by separate nerves, one of which has possi- 
bly to go a long way out of a direct course to reach it, which 




Fio. ^,— Fibers of 
Remak ; moffni' 
Jied 800 diame- 
ten, (Robin.) 

With the gelatinous 
fibers are seen 
two of the ordina- 
ry, dark-bordered 
nerve-fibers. 



>** Rett tad Pain,** London. (New York, 1879.) 



12 



GENERAL INTRODUVTIOK 



is contrary to the usual method of Nature, who always em- 
ploys the simplest means to accomplish her designs ; but, if 
we examine the action of these two muscles, we shall find 
that each one acts in unison with the other muscles supplied 
hy the same nerze^ and that to produce this perfect accord 
Nature takes what, to a hasty glance, would seem to be a 
needless step. 



Fio. C. — Mode o/ lerminaiion of tfn motor nerves. (Rougct.) 

Aj primitives faiidculuti of the thjro-hjoid muacte of the hiimati subject and ita nerve 
tube: 1^ I, primitive rniiscuiar fasM^ionlua; 2, perve tube; 3^ raodtillary siibstunee of 
the tube^ which ir* *eeti t'Xtetiding to the terminal [jl&te^ where it diwapficara ; 4^ ter- 
minal plflte s^iiuated beneath the* snrcolemmo, that ia to gaj, between it and the ele- 
mentary fibril lie ; 5, 5^ siircolenitiia. 

Bj pnniitive faseiculus of the intereostal mitsete of the liaard^ in which a nerve twbe ter- 
minatea: 1, 1, sheath of the nerve tube \ 2, nucleus of the sheath ; 3, 8^ garcolemma 
becoming continuous with the sheatb ; 4^ medullary j^Dbstanc*? of the nerre tube ceas- 
ing abruptly at the i^ite of the terminal plate ; 5^ 5^ terminal plate \ 6, C, nuclei of 
tha plate ; 7, 7, gninular substance which fonn8 the principal element of the termiiULl 
plate, and whien ia oontumoua with the axis cylinder ; 8, y, undulalionfl of the saroo- 
kmma reproducing tbofie of the fibriHsc ; 9, 9^ nuclei of the sarcsolemma. 

He also kiys down certain axioms, pertaining to the distri- 
bution of nerves and the diagnostic value of pain, which will 
be often repeated in these lectures, and can not but be most 
profitable to those who use them as a guide. They are aa 
follows : 

''Superficial pains on both sides of the body, which are 
symmetrical.^ imply an origin or cause, the seat of whieh is 
central or bilateral; while unilateral pain implies a seat of 
origin which is one-sided^ andy a^ a rtde, exists on the same 
side of the body as the pain J ^ 

The bearings of this first axiom will be rendered far more 
apparent when the regions of the neck and trunk are con- 



GENERAL INTRODUCTION. 13 

fiddered, since the symptom of local pain is of the greatest 
value in connection with diseases affecting the bones of the 
spinal column and the spinal cord which they invest ; but the 
same rule may be applied to any of the cranial nerves, with a 
degree of certainty which seldom admits of error. 

Thus Hilton reports a case where a fracture of the base of 
the skull, involving the orbit, produced amaurosis and tension 
of that region, with extreme local pain. A grooved probe, 
passed along the root of the orbit, revealed pus, as was sus- 
pected to exist. This was evacuated by the separation of the 
blades of an ordinary dressing forceps. 

As further examples of this axiom, a toothache may ac- 
company an inflamed condition of the temporo-maxillary 
articulation, or it may create it. Again, opium introduced 
into the auditory canal will often instantaneously relieve 
toothache and stiffness of the jaws, by having a narcotic 
effect upon the peripheral filaments of the same nerves, whose 
main trunks are distributed to the regions mentioned as re- 
lieved. 

Severe earache may result directly from the nervous irri- 
tation of a diseased tooth, since the filaments of the fifth 
nerve are distributed to both the ear and the teeth, and thus 
pain may be felt at a point apparently disconnected from the 
seat of irritation. 

Earache is frequently the result of malignant ulceration 
of the tongue, since both regions receive a portion of their 
nervous supply from the fifth cranial nerve. 

The second axiom is as follows : 

"7%e same trunJcs of nerves^ whose hrancTies supply the 
groups of muscles moving a joint, furnish also a distribution 
of nerves to the skin over the insertions of the same muscles; 
and the interior of the joint moved hy these muscles receives 
a nerve supply from the same source.^ 

By this axiom, a physiological harmony is created between 
these various cooperating structures. Thus any joint, when 
inflamed, may, by a reflex act through motor branches de- 
rived from the same trunk by which it is itself supplied, con- 

4 



14 GENERAL INTRODUCTION. 

trol the muscles which move it, and thus insure the rest and 
quiet necessary to its own repair. 

Spots of local tenderness in the cutaneous surjfdce may, 
for this reason, likewise be often considered as a g^ide to a 
source of irritation of some of the structures supplied by the 
same nerve, viz., the muscles underneath it, or the joints 
which are moved by them ; and thus even remote affections 
can be accurately determined, which, were this axiom not 
used as a guide, might escape recognition till an advanced 
stage of the disease had been reached. 

The distribution of nerves to the under surface of mnseles 
seems to be a rule, as Hilton points out, with comparatively 
few exceptions It is stated by Allen that the external 
oblique muscle of the abdomen and the abductor poUicis are 
exceptions. 

The shape of muscles seems to determine the method of 
nerve- endings, as was first pointed out by Schwalbe. Those 
muscles whose width exhibits little variation and whose fibers 
run parallel with one another receive only one nerve, which 
enters at its middle point. Those muscles that are of a tri- 
angular form, and whose libers converge toward a tendon at 
its apex, receive the nerve near to the attachment of the 
tendon. Hilton's axioms of neiTe distribution relate to the 
physiological distribution of nerves to muscles and the adja- 
cent skin. 

It is well, however, to quote one other axiom, laid down 
by the same author, before leaving the subject of the diag- 
nostic value of the cutaneous nerves as indicators of existing 
disease of other organs, viz. : 

^^ Etery fascia of the body has a muscle or muscles at- 
tached to it, and etery fascia must he considered as one cf 
the points of insertion of the muscles connected to it, in fol- 
lowing the previous axiom as to the cutaneous distribution 
of nerves." 

This guide is especially important in case the rule should 
be applied to the extremities (arms and legs) where these 
fasciae extend over large surfaces, more or less remote from, 



GENERAL INTRODUCTION. 15 

and apparently unconnected with, the muscles attached to 
them ; but it is mentioned in this connection, for the special 
object of calling your attention to those general rules which 
govern the distribution of the nerves in their entirety, before 
proceeding to apply them in all their individual bearings. 

Without this nervous association between the muscular 
structures and those composing the joints, there could be no 
intimation given by the internal parts of their exhaustion or 
fatigue. Again, through the medium of this same association 
between the skin and the muscles, great security is given to 
the joints, by the muscles being made aware of the point of 
contact of any extraneous force or violence. Their involun- 
tary contraction instinctively makes the tissues surrounding 
the joints tense and rigid, and this brings about an improved 
defense for the subjacent joint structures. 

Prom the conclusion of his great work, in which Hil- 
ton* endeavors to prove that mechanical rest may be used 
as a cure for most of the surgical disorders, the follow- 
ing sentences are quoted, since they can not be too often 
repeated: 

"I have endeavored to impress upon you the fact that 
e^ery pain has its distinct and pregnxint signification if we 
vdU hut car^uLly search for it 

'' Prom the pain which follows the intrusion of a particle 
of dust on to the conjunctiva, and the closure of the eyelid 
for the security of rest, up to the most formidable diseases 
which we have to treat, pain the monitor, and rest the cure, 
are starting-points for contemplation, which should ever be 
present to the mind of the surgeon." 

In studying the nervous system of man, the special consid- 
eration of the brain should first engage our attention, because 
it is by far the most diflBcult to thoroughly comprehend. 
Subsequently each of the twelve nerves of the cranium which 
arise from the brain-substance should be reviewed, and the 
more important facts presented by each, which may tend to 
elucidate its function or explain many direct and reflex 

> Op.<!%l, 



16 



6ENEMAL INTRODUCTIOIT, 



phenomena, should be understood. These are often of gretl 
value in the diagnosis of obscure aflfections. 

Later in the course, the anatomy of the spinal €K>rd and 
the nerves which arise from it should be investigiited ; noting 
in each instance, such points as tend to elucidate the f iinctif 
of the part under consideration, and also such clinical fad 
as can be constjintly applied in your daily adsoeiation wit 
the sick, when difficult questions of diagnosis arise, or wl 
valuable suggestions, as to the methods of treatment employe 
seem to be the direct outgrowth of your anatomical stncly. 

It lias become rather an established custom with late 
authors to reverse this order of study, as they €X>minonl] 
direct the attention of their readers first to the constructioD* 
of the spinal cord, which is much simpler than that of the 
brain. They then trace the nerve-strands which compose 
upward to their connections with the various parta of tl 
bmin. It must be acknowledged that this system has sona^ 
advantages over the one which I shall adopt; but it has alsi 
to my mind, certain distidvantages which have caused me 
vary from the moi'e common method of description. In ord€ 
to avoid any possibility of confusion, however, I shall be| 
my course with a general description of cerebral and spina 
architectuiu The diagmms which I shall employ to illus« 
trate this portion of the course will, I trust, prove of great 
sendee (Figs. 7, 8, 9, and 10), 

Some years since, my friend Prof, E. C. Seguin ad*^ 
dressed a class, in beginning a course ' upon a somewhat 
similar subject, with words of cotinsel and earnest pleading 
for higher professional attainments, which are well worthy oti 
repetition. I therefore quote them to you in the same sj^irifc, 
trusting that they will kindle in you a renewed viiror and, 
enthusiasm in this special department of science: 

*' In practice, when we have completed the examination of | 
a patient, seveml questions are put to us by the patient, bj 
his friends, or by ourselves. These are, in chronologic 

* Delivered before th« studeaU of tbo College of rhjsici&nfl tnd SurgeooB of ^t 
York City, ie7S. 



GENERAL INTRODUCTION ' 17 

order: Is there disease? Where is the disease? What is 
the disease ? What are we to do for the cure of the disease 
or for the relief of the patient? Will the patient die or 
recover ? 

"Of these questions, the one which our client and the 
world at large consider the most important is the fourth — that 
relating to treatment and cure. This preference is natural, 
but highly unscientific ; it is a manifestation of that untrained 
mental action which demands results and scorns methods, 
which welcomes empirical achievements (provided they be 
agreeable), and which conduces to the perpetuation of quack- 
ery of all kinds. But to the physician who is not a mere pre- 
scription writer, who aims at infusing as much science into 
his practice as possible, and who believes that he is not in 
the world for the purpose of gratifying his patients at so 
much per visit, but that he owes himself a debt of training 
and self-culture, and who has a sincere regard for science — to 
such a physician the first three questions assume a justly 
great importance. Pray observe that I do not say paramount 
importance, but great importance. And the superiority of 
the humanitarian over the scientific duty becomes less glaring 
if we bear in mind the truth — and I firmly believe it to be 
such — that success in treatment now depends, and in the 
future vrill still more closely depend, upon the scientific study 
of the human subject in health and disease. In other words, 
I would impress you with my own conviction that the best- 
trained and most scientific physician, if he be not a closet 
student and theorizer, is the best practitioner. 

*'We occasionally hear of an over-fine diagnosis, of ex- 
treme caution in the treatment of disease, and of the sweep- 
ing application of physiological laws to practice by men who 
are said to be ' too scientific' ; but who can number the errors, 
nay, the sacrifices of life, which must be laid at the door of 
the falsely so-called 'practical men,' who despise learning 
and scientific methods ? Those of us who see something of 
the rarer and more formidable kinds of disease fully realize 
that in medicine, as probably in other applicable sciences. 



18 GEXERAL INTRODUCTION. 

ignorance leads to rashness and crudity in practice, while ripe 
knowledge conduces to success, or, at any rate, to <;^ntion in 
prognosis and expectancy in treatment. 

''Of the three diagnostic questions— Is there diseased 
Where is the disease { What is the disease ? — the second is 
the one which forms the key note of these lectures. AVhere 
is tlie lesion producing the disordered actions or symptoms \ 
The method to be followed in arriving at the solution of this 
question varies somewhat in different departments of medi- 
cine. Some lesions can be seen by the trained unaided eye, 
or felt by the skilled hand ; the seat of others can be deter- 
mined by auscultation and percussion, by the aid of instru- 
ments, such as the ophthalmoscope, laryngoscope, speculum, 
etc. But, in the study of the ner\^ous system, greater diflBcul- 
ties are met with ; we are, to a great extent, deprived of these 
l)hysical aids; we can not apjueciate the condition of the 
brain and spinal cord dire(*tly h\ our special senses, but only 
by a proper interpretation of the way in which the functions 
of thes(i j)aits aie i)erformed. In other words, the diagnosis 
must be made cliiefly l)y reasoning." 

To the words al)<>ve quoted, I can add nothing, save an 
earnest endeavor to so place the subject-matter before yon as 
to render it within the grasp of your full comprehension, pro- 
vided you, in turn, earnestly seek to master it. 



THE BRAIN. 

ITS ANATOMY, FUNCTIONS, AND CLINICAL ASPECTS. 



THE BEAIIS". 



In man and the vertebrates, the cerebro-spinal axis may 
be divided into three separate portions, each perfectly inde- 
pendent of one another, and yet very intimately connected. 
These are enumerated by Meynert as follows : 

1. The cerebrum. 

2. The cerebellum, and the apparatuses of cere- 
bellar INNERVATION CONNECTED WITH IT. 

3. The medullary portion of the spinal cord, and 
ITS expansions to the different parts of the en- 
cephalon. 

The nervous system of all animals may be subdivided 
into two distinct histological elements, nerve-cells and nerve- 
fibers. The former may be compared to the battery-cells of 
an electric circuit ; the latter to the wires which conduct the 
current generated in the batteries. 

The nerve-cells are the chief histological elements of the 
so-called "gray matter" of the brain and spinal cord, and of 
ganglia found in other parts ; while the white substance of 
the cerebro-8i)inal axis may be subdivided by the microscope 
into distinct fibers, which serve to connect the nerve-cells of 
sqme particular region with other nerve-cells or with the 
muscular apparatus. 

Nervous impulses may be divided into two classes : cen- 
tripetal or sensory^ and centrifugal or motor. 

The former travel from the peripheral portions of the 
body toward the nerve-centers; while the latter cause the 



I 



22 THE BRAIN. 

muscular apparatus of the body to act, either in direct re- 
sponse to a sensory impression received from without {^reflex 
7novevients\ or as the result of volition. Microscopical re- 
search enables us to state positively that both of these two 
forms of nervous impulses are conducted partly through 
direct tracts of nerve-fibers, and partly by the intercommuni- 
cation established between nerve-fibers and nerve-cells, and 
nerve-cells with each other. 

We may infer, therefore, that nerve-cells as well as nerve- 
fibers serve to maintain isolated conduction of nerve impulses; 
and that the former also generate and in some instances record 
them (cells of memory). We find the morphological expres- 
sion of the first statement in the fact that the nerve-cells lie 
with their long axis stretched in the direction of the nerve- 
fibers with which they are c(mnected ; while the second and 
third propositions are established by physiological research 
respecting the functions of different regions of the cerebral 
cortex, as well as by the general arrangement of the cell ele- 
ments. We are forced, moreover, to accord to the nerve-cell 
the functional attribute of ^^efisibilit?/, as well as the power 
of generation and storage of nerveforce^ and the discTiarge 
of this unknown power in thvform of motor impulses. 

There is sufficient ground at ])reserit to warrant the belief 
that all centripetal- and centrifugal-conducting nerve-tracts 
are prolonged (in spite of apparent dismemberments and 
reduplications to which the white substance of the cerebro- 
spinal system is subjected in passing through different col- 
lections of gray matter scattered along their course) to the 
most distant centei-s of the nervous mechanism, and find a 
direct and intimate connection with the nerve-cells of the 
gray substance of the cerebral convolutions. 

It seems but rational to assume that the phenomena of 
consciousness^ which spring purely from the confluence and 
union of the various processes of perception, have their seat 
in the activity of the cerebral lobes ; to which all the cen- 
tripetal or sensory tracts converge and from which all the 
centrifugal or motor tracts arise. 



GRAY MATTER OF THE BRAIN. 23 

If we study transparent sections of the brains of small 
mammals, where the different portions are more clearly de- 
fined than in animals of a higher type, and where a low 




Fio. 6. — Plan in atUHne of (Jte hrain in profile. (QuaixL) 

The cerebrum is represented in this diagram as separated from the cerebellum more than 
it naturally should be, in order to show certain important parts. A, the cerebrum ; 
B, the cerebellum; C, the pons Varolii; D, the medulla oblongata; E, the cms 
cerebri ; F, the olivary body ; 6, the tubercula quadri^cniina ; S, the fissure of Syl- 
vius ; R, the fissure of Rolando ; a, peduncles of the cerebrum ; h^ superior pedun- 
cles of the cerebellum ; c, middle peduncle of the cerebellum ; </, inferior peduncles 
of the cerebellum ; 6, E, a, form the isthmus cncephali. The convolutions of the 
cerebrum are not correctly drawn in this cot 

magnifying power reveals the general course of the nerve- 
fibers as well as the arrangement of the masses of gray mat- 
ter, we are enabled to grasp some general features of con- 
struction which are applicable to the brain of man. 

THE GRAY MATTER OF THE BRAIN. 

We find, in the first place, that the nerve-cells occur in 
large and distinctly isolated masses, which may be thus 
enumerated : 

1. The gray matter of the exterior of the cerebrum (the 
cortex cerebri) that invests the convolutions. This collection 
of cells, as an undulating layer folded constantly upon itself, 
forms a layer, marked by eminences and depressions whose 
sole object is to obtain an increase of the brain's surface over 
that of the interior of the cranium. 



u 



TEE BRATK 



2. Buried within the substtmre of each henjisphere of the 
cerebrum may be foinul two nodal masses of cells, which rest 
nearly uimn the level of the floor of the cerebrum, and which 
are named, from their contiguity to this plajie, the ^^dofol 



.w<^^ 



COf^TEJ^ aPf!>Afii, 



''^r^i 



.^^^s 



OF THS. C£HES Ri 



lUili/JM 



^9K' 



9»LONOATA 



'^^u. 



j CO A a 



\q, 7,— -i ditipram di^hjncd by the auth*r to ffncidatfi (he thtff tomponeni p&ri$^pf 

(ht human brain. 

The lettering upon the fif^uro will be explained Iti the irxr, C. Q., the corponi qimcirB. 
gerotniLf or "optic lolics.'* The line* witiiin the whilt" Hubstauce of the cerebrum or 
in the **crad^* are nut mtended to convey any Injpreafiiou to the revtiier of the acciml 
Arrangement of the tibcrd. 

Each anterior mass is called the ^^ corpus strialum^^^ from 
the striated appearance of a section made through its sub- 
stance/ J 

Each posterior mass is called the ^"^ optic thalamus^" from 
a supposed association with vision attributed to it by early 
investigators. 

^ ThU ganglion hue two parU (m ihown in Fig. B)— the mwtatti nuciew, and lenficfti4n» 
mmiew. These pArto tati tfpftnUtd hj m huatllc of nerve^Ilbers, tht MHwlled ^* ihUm^ 
ca§m»U** of tbo oerebmiD, 



FIBERS OF THE CEBEBRO-SPINAL SYSTEM. 



25 




Flo. 8. — A diatom detipned by the auihar to thow the general arrangement of ike 
fiben of the eerebro-epinal eyetem. (Modified from Landois.) 

The shaded portions represent the collections of gray matter. On the left side of the 
diagram, the eeneory fihere of the cms are traced upward from the spinal cord to 
different portions of the cerebrum ; on the right side, the motor fihere are similarly 
represented. Numerals are uxed iu designating the eeneory and commi»eur<U fihere ; 
the. motor fihere are lettered iu small type. The cortical layer is shown at the 
periphery of the cerebral section, with commissural fibers (1) connecting homologous 
regions of the hemi.'ipheres, and associating fibers {a, ».) connecting different conTo- 
Itttions of each hemisphere. G.N.,<»tf<2ti/«nuW^<«of thccoRPCS atriatcm ; L. N., letv- 
tieular nucfeve of the same ; 0. T., optic thalamus of each hemisphere, united to its 
fellow in the median line; e. 9., corpora quadkigexina ; c. /., clausteum, lying to 
the right of the letters ; c. c, corpus callosum, with its commissural fibers ; 8^ ns- 



26 THE BRAIK 

dURS OF Stlyius; F, lateral ventricle, the fifth ventricle being shown betveeo 
the two layers of the BCfAnm luddum ; C\ the motor trad of the crub cerebri {ham 
eruri» — cruista)\ T^ the seiuori/ tract of the CRUS cerebri (ftf^^memium ctuHm); (Y, 
the cerebelfar jfagciculus^ which is turned to the right for perspicnltj, bat which n 
reality decussates ; e^ the point of decussation of the motor fibers of the spiul 
cord ; /, the course of the motor Jihers of the spinal cord below the medullm, Hhovio^ 
their c*onncction with tlie cells of the anterior horns of the gray matter, and tbcir 
continuation into the anterior roots of the npinal nerves (g)\ a, fibers which radiate 
throu;;h the caudate nucleus; 6, fit)er8 of the ^^ internal eapnUe^^^ e^ fibers wUch 
radiate through the lenticular nucleus ; d^ fibers of the *' extemai eapmUe ** ; 2, 8, 4, 
A, 6, 7, 8, 9, sensory fibers radiating from the tegmentum cmris to the cortex br 
means of various nodal masses of gray matter ; 1 1, course of the scnsorj fiben i. 
the spinal cord (shown by dotted lines), intimately connected with the posterior root 
of the spinal nerve (12), and decussating at or near the point of entrance into the 
spinal cord. This diagram may be studied in connection with Figs. 7, 9, ]0 11, 
and 1 8, with possible benefit to the general reader. 

3. The cerebellum presents collections of gray matter 
which occur partly in layers {cerebellar cortex) and partly as 
scattered masses within its substance. 

4. The so-called ^^ tubular gray matter'*^ (which may be 
traced as a lining to the inner portions of the cerebro-spinjol 
axis * from the tuber (jinereum to the conus medullaris of the 
spinal cord) must be recognized as tlie "permanent expression 
of the primitive and generic type of brain." 

5. Distinct groups of cells are found within the substance 
of the rrus cerebri, the i)ons Varolii, and the medulla. These 
will l)e discu^ssed later. 

The diagram (IMg. 8) will make some of these subdivisions 
of the gniy matter of the cerel)rum, as well as the fibers 
whi(!h connect them, more apparent than a long verbal de- 
scription. 

It will be seen that the gray matter of the cortex is 
aiTanged like a cap to the bi-ain, and embi'aces the ^^ basal 

ganglia," the ''claustrum,'" find ''coi'jmi-a quadrigemina" 

intermediate portions l)eing left which in the brain itself 
api)ear as a white, chec^sy mass. These are filled in with lines 
in the diagi-am. They indicate the different sets or ** sys- 
tems" of nerve-fibers, as the microscope in the hands of late 
observers has shown them to exist, and of which this so- 
called ''ic/iite substa?irr'^ of the bitiin is chiefly composed. 
[A careful study of the text accompanying Figs. 8, 9, and 10 

' Tho ** cerobro-spinal axis " is a term used to include the brain and the spinal ooid 
collectively. 



WHITE MATTER OF THE OEEEBRUM. 



27 



will enable the reader to grasp the general direction and 
terminations of the sets of fibers described.] 




PiQ. 9. — Diagram of the eommisaural fibers of the anUrwr region of the brain, 

(After Luys.) 

These form a series of ounres one within another, the extremities of each of which plunge 
into the homologous regions of each cerebral lobe, 1, l\ 2, 2\ 8 and S', They pass 
through the middle line, and at 4 and 4' give rise to the various appearances which 
the ** corpus callosum*' presents. 6, Commissural fibers of the inferior regions. 
These are curved in an inverse direction as regards the former, the convexity of 
each set being presented toward that of the other. 



THE WHITE MATTER OF THE CEREBRUM. 

The FIRST SET OF FIBERS (1 in Pig. 8) will be seen to 
spring from the cortex, and, after taking a direction which 
tends to bring them to the level of the superior point of union 
of the two cerebral hemispheres, to cross over to the side 
opposite to that from which they arise. After crossing, they 
can be traced to homologous regions of the cortex of the 
opposite hemisphere. These are commonly called '^ commis- 
sural fibers.^ They are supposed to be the connecting wires 
between corresponding portions of the cortex of the cerebral 
lobes, by the aid of which the right and left hemispheres can 
act in unison with each other when circumstances chance to 
demand it. 

These fibers have a direction which corresponds as a rule 
to the form of the letter U, and they constitute the transverse 
fibers of the '^corpus callosum^^ — the connecting band of 
white matter between the hemispheres, seen at the bottom 



I 



28 TEE BJUIK 

of the median fissure of the ceiebram when the hemisphereB 
are separated. Commissural fibers can be traced also between 
the hemispheres (in certain sections of the brain) as an infe- 
rior band * which lies below the level of the ** basal ganglia* 
(Pig. 10). 

There is reason to believe that these connecting fibers 
(which form nearly if not quite one half of the white sub- 
stance of the cerebrum) are sufficient, in point of number, to 
allow of an anastomosis of the gray matter of the cortex of 
the two cerebral lohes^ cell to cell. In infinite numbers they 
seem to spring from every region of the cortex — either directly 
from the protoplasmic structure of the cell elements, or as 
delicate fibrils which can be traced no farther than the inter- 
cellular structure, where their delicate sheaths become lost 
(Luys.) 

The SECOND SET OF FIBERS (Fig. 8) ib which I would now 
direct attention are of equal importance from a physiological 
point of view. Originating from the midst of a plexus of 
cells in the cortex, they accompany the commissural fibers 
to the point where tlie foi-mer diverge to the opx>osite hemi- 
sphere, after which a separation takes place. These fibers 
do not pass to the opposite hemisphere^ but concentrate them- 
selves, in the region of the superior angle of the ventricle, 
into bundles placed in close juxtaposition. Some of these 
fibers are inserted, as a late author expresses it, like "pins in 
a pin-cushion," into the basal ganglia of the hemisphere from 
whose periphery they take their origin. Others seem to 
have no anatomical rehitionship with the basal ganglia. They 
are known as the ''capsular fibers"; l)ecause they constitute 
a capsule, as it were, for the lenticular nucleus (Fig. 8). 

The second set of fibers (if taken collectively) are com- 
monly called ^^ radiating fiber s^^^ from an analogy between 
the direction which they take and the rays of light reflected 
from the surface of a hollow sphere. By some authors they 

' Thifl may help to explain the fact that the ahnenee of the corpiu caUotntm has in 
exceptional cades been observed to exist without any apparent abnormality in the per- 
formance of psychical or motor phenomena during life. 



RADIATING FIBERS. 



29 



are designated as *'^ converging flhers^'^^ because they tend to 
become focused about the basal ganglia. By others the term 
^^ peduncular flhers " is employed, because they are destined 
to pass into the eras cerebri. 




Fig. 10. — Diagram of the eommiMural fiben en the level of the carpue etriahim, (Lujs.) 

1, r, ffroups of innsTeree fibers, one within another, continuous with those in the pre- 
Tious fiffure; 2, 2', my substance of corpus striatum; 8', groups of inferior com- 
missural fibers ; 4, 4^, these curve into the shape of an 8 to accommodate the corpus 
striatum, which they help to limit externally. 

By directing our attention for a moment to the fact that 
fibers which are distributed to all portions of the cortex are 
forced to make their passage from and into the spinal cord 
through the foramen magnum, in case they are distributed 
to parts below the head, we shall be led to understand why 
the peduncular set are properly converging fibers before they 
become collected into the circumscribed limits necessary for 
their transmission, through this foramen of the cranium, to 
reach the spinal cord. 

It is important to bear in mind that this set of fibers has 
nothihg in cammon witJt the opposite hemispheie. The phys- 
iological function of the peduncular fibers of the cerebrum 
consists simply in the transmission of impulses of a centripetal 
and centrifugal variety to and from the cortex cerebri. It is 
by means of these nerves that sensory impressions received 

5 



30 TEE BRAIN. 

front without are recorded upon the sensory portioiis of the 
<.'ortex, and motor impulses are transmitted from the motor 
regions of the cc»rtex to the muscles of the trank and ex- 
tremities. As Meynert aptly puts it, "the sensory nerve- 
lil>ei-s constitute the feelers of the cortical cells, the motor 
nerves, the tentacles, as it wei-e.' ■ 

A THIRD SET OF FIBERS (Figs. 8 and 13) exist within the 
white substance of the cerebral lobes. They are called **a*- 
Hociat lag fibers'^ {'\fibrce arcuatce^ — ""^ coUateral fibers^), 

ac 




Fig. 11. — A dlagr'ini to iUnAira(e the (jeueml outVmc of the corpus eallotum amd the 

fornix. (Moditied from Allen.) 

F, foruix. (•xtendin^r from tip of tcinporal lobe to tlie hase of the brain, anteriorly. The 
i-avity of tln.r tliinl ventridt' lio> below its mi(Mle thirtl. (.'., corpus caUosuin, forro- 
iiiir tin; roof of thi* liUeral ventricles and merging posteriorly with the fornix; C. C 
ceix'hral eortfx ; f. M., foramen of Mtmro, joininjr the lateral ventricle with the third 
vi-ntriele ; p. f., anterior pillar of the fornix, doubling upon itself and returning to 
the thalamus. All of tliese parts will be described in detail later in this Toluine. 

These, as was the case with the preceding set, are confined 
exclusively t(» the hemisphere in which they are found. They 
are sui)p<)sed to be so distributed to the different portions of 
the cortex of (»ach hemisphere as to act as commU sural fibers 
for the different cortical centers. Whether they are always 
distinct til)ei*s, or simply thread-like anastomoses of the pro- 
cesses arising from the cells of the cortex, is not as yet fully 
detei-mined. By some authors these lil)ers are described as 
dii)i)ing downward for some distance into the white substance 
of the h(»misi)heres and then returning to the cortex, while 
others describe them as bundles of distinct fibers of varying 
lengths which invest the inner surface of the cortex. 



THE PROJECTION SYSTEM. 31 

Finally, attention should be called to a fourth set of 
FIBERS that apparently serve to connect the cortex of the 
temporo-sphenoidal lobes with the optic thalamus by taking 
an arched direction over that ganglion, and then dipping 
downward to the base of the brain where they turn upon 
themselves and pass to the substance of the thalamus. Why 
these so-called ^'fornix fibers^ should take this circuitous 
route in order to establish communication between the basal 
ganglia and the temporal cortex is not, as yet, understood. 
The fornix will be discussed more in detail in subsequent 
pages. It is shown diagrammatically in Pig. 11. 

The Projection Systems. — The cerebral cortex or the 
gray matter covering the convolutions serves as a receptacle 
for the various impressions of the external world, as por- 
trayed to it by means of the nerves of sensation and the 
special senses. It has been considered, therefore, by Meynert 
as analogous to a projection plane^ the outer world being 
the projected object ; and the nervous system has been sub- 
divided by the same author into three distinct members of a 
so-called ''^ projection system^^^ comprising nerve-fibers and 
various ganglia interposed along the course of the centripetal 
and centrifugal nerve-tracts. The views of this author may 
be stated as follows : 

The first member of the projection system (Pig. 12) con- 
sists of the fibers which are connected with the cortex and 
which terminate chiefly in the interrupting gray matter of the 
basal ganglia. 

The second member of the system comprises those fibers 
of the cms cerebri, which spring from the basal ganglia and 
end in the tubular gray substance. These fibers terminate 
in the tubular gray substance at different levels in order to 
become functionally associated with different parts of the 
body. It must be evident, therefore, that the length of these 
fibers depends entirely upon the portion of the periphery 
with which they are associated. Most of these fibers are 
supposed to cross the median line to reach the opposite side 
of the spinal cord. 



82 



THE BRAIK 



The third mefwber of the system embraces the nerres which 
arise from the tubular gray matter ; from the i)oint of origin 
of the third cranial nerves to the termination of the spinal 
oordL 




-{ 



Fiber of 

^^ tuperior prt^feo' 

Hon tjfdem,*^ 



fCeir 
fBa8at\ 



MU80LE8,\ 

Skot, 

OSOANS, 



Fiber of 

" nUddU proj«o- 

Hon 8t/demJ*^ 




Ve7T 

ofSprifatj 
rdJ 



I V 3 ^^ inferior prryt 

J (_ tion 8y&temy 



Fio. 12. — A aehentaiic representation of MeynerCs three projection iyttemt of nerve-fhen, 

Spitzka's classification of the systems of projection tracts 
and the ganglia associated with them* differs from that of 
Meynert (1) in that he numbers them in accordance with 
their priority of development, classing the central tubular 
gray and the spinal nerves as the first projection system ; 
(2) in that he considers the gray masses of the reticular for- 
mation of the medulla (the reticular ganglion of this author) 
as belonging to a special category ; (3) in that the cerebellar 
system is incorporated by this author and excluded from the 
plan of Meynert ; and (4) that the number of the projection 
systems is increased. 



* Jour, of Nervous and Mental Diseases," Oct., 1879. 



SPITZKA'8 CLASSIFICATION. 33 

There is much to be said in favor of the classification of 
Spitzka, although it is perhaps more difficult of comprehen- 
sion to the minds of beginners in neuro-anatomy because 
more complete. The following scheme is employed by that 
author to interpret his views respecting the incorporation of 
the reticular ganglion in the projection plan : 



RETICULAR GANGLION 

OF THE 

MEDULLA OBLONGATA 



STRAND UNITINQ THE RETICULAR QANQLION 
WITH THE CENTRAL TUBULAR QRAY 



CENTRAL 
TUBULAR GRAY 



< PERIPHERAL NERVE 



PERIPHERY. 

Space will not allow of the incorporation of all the ex- 
cellent diagrams devised by this author to illustrate his 
views. They can be referred to in the article from which 



;u 



THE BBAIN. 



the above is taken. One other will, however, be intio- 
duced to show that author^s views lespectiii^ the com- 
munications between the " reticular ganglion " and the nu- 
clei of the cranial nerve-roots: 



2nd Category 



RETICULAR GANQUON 

OF THE 

MEDULLA OBLONGATA 



fst 
Category 



SECONDARY 

PROJECTION 

TRACTS 



NUCLEI 

OF THE 

MEDULLA OBLONGATA 



GRAY SUBSTANCE 

OF THE 

SPINAL CORD 



PRIMARY PROJECTION 
TRACTS 



PERIPHERY. 



NERVE-CELLS. 35 

The schematic representation of nerve-tracts thus ex- 
hibited (if extended cephalad) would include, according to 
Spitzka, the thalamus as the 4th category, the corpus striatum 
as the 5th category, and the cortex of the cerebrum as the 
6th category. The corpus striatum is placed above the 
thalamus because certain fibers pass through the latter to 
reach the former. 

It will be perceived that the superior member of the system 
properly embraces the fibers of the cerebral lobes — the com- 
missural, radiating, and associating systems of fibers (Pig. 8). 
It is probable, moreover, that the gray matter of the cere- 
bellum (chiefly that of the cerebellar cortex) is intimately con- 
nected with the cortex of the cerebrum by stiU another set of 
fibers, which constitute a distinct formation, but the ramifi- 
cations of which can not be so described in this general intro- 
duction as to be easily comprehended in all of their anatomical 
relations. 

It may be asked, '* Why is there a necessity for the break- 
ing of the nerve-fibers and the introduction of cell-elements in 
the course of a tract which might be continuous?" *' What is 
the object of so disturbing the simplest form of arrangement?" 
" What is the function of the nerve-cells so interposed ? " 

It is not possible, with our present knowledge, to answer 
all of these inquiries to our complete satisfaction. We have, 
however, sufficient data for the conclusion, at least, that these 
interruptions in the course of nerve-fibers are not solely for 
the purpose of effecting a simple interchange of excitations 
between different groups of ganglion-cells, placed one above 
the other, as buckets are passed up and down a ladder from 
hand to hand (using an illustration borrowed on account of 
its aptness). There is a morphological significance, not to be 
overlooked, in these interruptions, which can often be demon- 
strated. These interposed cells possess the power of deflecting 
the current passing along the nerves to which they are at- 
tached, as the switch is used in telegraphy and on railroads. 
By the use of this simple device, centripetal and centrifugal 
currents may be allowed to pass without interrui)tion when 



36 



THE BRA IK. 



necessity demands it; or, again, the direction of the cui 
may be changed, and transmitted (through some other cue 
nection which the cell possesses by means of fibers attache 
to some other of its processes) to a point not situated upG 
the direct line of the paths of the projection system. 



^l 



Fio. IS. — DiapwftmaHe rrprriKnttiik»i of th fitrrt in the ctrftjrum. (Le Bod.) 

We have reason, also, to believe that each nodal mass 
%ray matter has an untumatism of its own^ by which it can 
influence the nerve-fibers in intimate association with it with- 
ont the intervention of the larger ganglia above, which are 
some instances capable of controlling it when necessarj% 



GENERAL ABRANG£M£NT OF THB FtDEHiS OF THE PROJECTION STSTHI 

The systems of nerve-fibei's found in the cerebnil lob^ 
have already been discnssed at some length, but certain addil 
tional facts pertiiining to the ** radiating system '* (Pig, 



GENERAL ARRANGEMENT OF FIBERS. 37 

remain untold. Sections of the cerebrum are of aid in map- 
ping out various bundles into which the radiating fibers are 
grouped. We are enabled to determine with ease a group 
connected with the "caudate nucleus" and one also with the 
"lenticular nucleus" of each hemisphere (the two masses of 
gray matter which together form the "corpus striatum"); 
again, one connected with the "optic thalamus" and the ad- 
jacent "corpus quadrigeminum " ; and, finally, a bundle of 
fibers whose course differs from that of the others— those of 
the "foroix." The latter appear to connect certain regions of 
the cortex with the anterior tubercle of the optic thalamus, 
and a mass of gray matter at the base of the brain, called the 
""^ mammillary tuhercle^^ or '^corpus candicans^^ (Pig. 11). 

It is now believed that some of the radiating fibers (those 
of the internal and external capsule of the cerebrum) are con- 
tinued directly from the cortex to the cms without the inter- 
vention of ganglion-cells.* The diagram now introduced (Fig. 
14) will aid in following these details. 

In the second member of the projection system — the " crus 
cerebrr' — marked alterations maybe observed, in regard to 
the number, course, and arrangement of the nerve-fibers, from 
those of the cerebrum. 

The actual number of fibers seems to be markedly reduced 
by passage from the white substance of the cerebral hemi- 
spheres through the substance of the basal ganglia. The fibers 
are, moreover, gathered into two bundles in the crus ; whereas, 
in the cerebrum, they form several bundles before the inter- 
ruption of these ganglia. 

The two bundles of the crus have been named by Meynert 
the ^^ basis cnirfs^^ (the "cnista") and the '-'' tegmentum 
cruris^'*^ from their relative position to each other (Fig. 14). 
The fibers of the former are connected chiefly with the nuclei 
of the corpus striatum (as can be seen in the diagram), which 
constitute its crown, as it were. Those of the latter (the teg- 

' The latest inTcstiiratioiis of FIcchsip seem to prove conclusively that this Ptatement 
is true of the pyrainidnl tractn. Ho locator) the Hittiation of these fibers in the middle 
third of the internal capsule, slightly posterior to its knee. 



38 



THE BRAIN. 



mentum cruris) are connected chiefly with the optic thalamns 
or the corpus quadrigeminum. 

Physiologically, the basis cruris or crusta (Pig. 14) may be 
regarded as a centrifugal or motor tract, and the tegmentum 
cruris (Fig. 14) as a centripetal or sensory tract. This state- 
ment is not absolutely correct, but it is practically advisable 
to so regaid it. 




Fio. 11. — Diafjram of the course of snimrtf and motor tracta in the metocephaian and 

hem isph > / •<». ( Si^-guin. ) 

S, sensory tract in posterior region of mesocvphalon^ extending to and T, occipital and 
temporal lob(»< of lu-niispheres ; M, motor tract in ha.*«is cruris, extending to P and 
F, parietal and (part of) frontal lobes of hemispheres ; (\ Q., corpus quadrigeniintun ; 
O. T., optic thalamus; X. L., nucleus Icnticularis ; X. C, nucleus caudatus; 1, the 
fibers forming the "tc*rmentum cruris" (Meyucrt); 2, the fibers forming the '^ basis 
cruris" (Mcynert). 



In studying the brains of mammals, these two bundles of 
fibers and the ganglia connected with them give evidence of 
an independence of one another which governs the develop- 
ment of each. Where tlie fnmtal and parietal lobt?s are large, 
we find the ''basis cruris'' and the two nuclei of tlie '' corpus 
striatum " (Figs. 8 and 14) highly develoi)ed ; on the other 
hand, when these lobes are at their minimum we find the 
''tegmentum cruris" and its ganglia develoi)ed in excess. 



PROJECTION TRACTS OF CEREBRUM. 



39 



There is also physiological evidence to sustain the opinion 
that the basal ganglia and the two bundles of the cms are 
capable in themselves of executing, in response to excitation 
from without, all varieties of movements in^n animal deprived 
of its cerebral lobes (above the level of the basal ganglia) with 
a nicety and exactness which are astonishing. 

The " cms cerebri" suffers a diminution in the fibers of its 
motor bundle (basis cruris) after its entrance into the sub- 
stance of the pons Varolii. This is very apparent when the 
large size of the tract, before its entrance into the pons, is 
contrasted with the small anterior pyramid of the medulla 
oblongata, which is its direct continuation after its exit 
(Pig. 6). The explanation of this fact is as follows: All of the 




!^^^^.,;.^^^^^^^^^^^^ 








Fio. 15. — A diagram of the brain in transverse vertical section. (Dalton.) 

1, cni8 cerebri; 2, internal capHule; 8, optic thalamus; 4, caudate nucleus of corpus 
ttriatum ; C. C, corpus callosum ; L. N., lenticular nucleus of corpus striatum ; S, 
fiBsure of Sylvius; Fo, gyrus fomicatus; Vy first frontal convolution; ¥'\ second 
frontal convolution ; F"\ third frontal convolution; T\ first temporal convolution; 
T", second temporal convolution; T"\ third temporal convolution; H, gyrus hip- 
pocampi. 



peduncular fibers of the cerebram, which become intermingled 
with the gray matter of the corpus striatum (the caudate and 
lenticular nuclei), and which escape from tliat ganglion as 
fibers of the basis cruris (Figs. 6 and 14), are not destined to 
form parts of the projection system. 



40 THE BRAIN. 

The ganglion-cells of the pons Varolii exercise, in the case 
of some special cerebral fibers," the switch-like action previ- 
ously referred to, and deflect the impulses, which they cairy, 
to the opposite hemisphere of the cerebellum ; hence, in the 
pons, quite a large bundle of distinct fibers appear to leave 
the direct tract of the basis cruris (Pig. 14) and pass to the 
cerebellum (through the processus e cerebeUo ad pontem). 
We have come to learn that a communication between the 
cerebral cortex and that ganglion is thus established, but its 
physiological function is not yet ascertained with scientific 
exactness. This fact, in addition to others which will be 
brought forward later^ leads to the conclusion that the cere- 
bellum is, in some imperfectly understood way, brought into 
direct relation with the motor tmct of the projection system 
of the cerebrum, and is endowed with some power either of 
control of or subtle influence over motor impulses.* 

If we examine cross-sections of the ^'i)ons Varolii" and 
*' crura/' we shall perceive that the pons i)erforms for the 
cerebellum an oflice analogous to that which the corpus cal- 
losuni perfonus for the cerebral hemispheres — ^the transmis- 
sion of rommi,s,sural fibers which possibly connect homologous 
portions of the two lobes, although they seem to become united 
with the cells of the gray substance of the pons. We may 
note, furthermore, that these commissural fil)ers of the pons 
subdivide the fil)ers of the basis cruris and tegmentum cruris 
into smaller bundles or fasciculi. In addition, nodal masses 
of gray matter mny be detected in both the cms and pons. 

It is reasonable, therefore, to conclude that the cells of 
these nodal masses of gray substance establish some form of 

' The!*c fibers are cliiefly grou|>ed during tlieir pasiaage through the lower part of the 
cerebral hemisphere wiihin th<» anterior half of the? internal capsule. Tiie fibers which 
arise from the cerebral cortex an<l apparently terminate in the gray matter of the pons, 
seem to spring in part from the fnmtal lobe and in part from the parietal and temporo- 
sphcnoidal lobes. The frontal fibers pass through the anterior half of the internal 
capsule, and, after their escape from the cerebrum, occupy the inner one third of the 
basis cruris. The fibers from the parietal and temi>oro-sphenoidal 1oIh>s pass through 
the posterior half of the internal capsule, and occupy (after their escape from the cere- 
brum) the outer one third of the basis cniris. 

' This subject will be discussed in connection with the architecture of the cerebellum. 



PROJECTION TRACTS OF CEREBRUM. 41 

communication between the fibers of the cerebral projection 
tracts and the commissural fibers of the cerebellum, indepen- 
dent of the fibers of the basis cruris which api)ear to deflect 
themselves from the path of the projection system into its 
substance. 

The cerebellum, furthermore, has undoubted association 
with special fibers of the cerebrum (which are prolonged, sub- 
sequently, into the basis and tegmentum cruris) by means of 
two of its prolongations, viz., the processtcs e cerebeUo ad 
testes and the talte of Vieussens. The multiplicity of connec/- 
tions which this ganglion has with fibers of the projection sys- 
tem leaves its probable functions a matter of si)eculation. The 
theories advanced will merit consideration later in the course. 

Finally, the ganglia of the brain have intimate relation 
with certain nerve-tracts which are indei)endent of the projec- 
tion system proi)er — viz., th^JWers of special cranial nerves ^ 
which are more or less independent of the tubular gray 
matter. 

The olfactory, optic, and auditory apparatuses must be 
considered, therefore, as modified tyi)es of projection systems, 
which bear, however, striking analogies to the projection sys- 
tem extending to nerves of spinal origin, although possessing 
I)eculiarities of structure essentially their own (Fig. 12). In 
these modifications of the general arrangement, the middle 
projection fibers appear, at a first glance, to be wanting, as 
there is with some cranial nerves, as far as we at present 
know, no organ which corresponds exactly with the central 
gray tube of Meynert's projection system. Many observers, 
however, incline to the view that the peripheral ganglion-cells 
are analogous to the tubular gray matter. These consider, 
for example, the fibers of the optic tract as a middle system 
of projection, and the radiating fibers in the retina as the 
external system of projection. 

The projection tracts of the cniff are prolonged into the 
medulla oblongata and spinal cord (Fig. 8), where they be- 
come more or less intimately associated \^ith the tubular gray 
matter. 



42 THE BEAIN. 

The third member of the prqjection system exhibits an 
aagmentation in the actual number of fibers over those found 
in the crus ; as there can be no doubt that the total number of 
fibers in the spinal nerves exceed greatly those comprised in 
the basis and tegmentum cruris. Here, again, we have undis- 
pu table evidence that the gray matter of the spinal cord, by 
means of its cell elements, serves as a means of conduction of 
nerve impulses, and also as a point of origin for additional 
nerves, whenever demanded. 

The motor tracts of the basis cruris become joined to cells 
in the gray matter of the spinal cord, which are connected 
with the anterior or motor roots of the spinal nerves (see 
Fig. 8). The fibers of the tegmentum cruris unite with simi- 
lar cells which lie more posteriorly, and are associated with 
the posterior or sensory roots of the cranial and spinal nerves 
(see Pig. 8). The individual course of the various bundles 
(that help to form the motor and sensory tracts of the crus 
cerebri) throu<rh the medulla and spinal cord will be described 
in subsequent i)af»:es. 

It may be well, however, to state in general terms that 
each separate nerve-fiber which properly belongs to the pro- 
jec^tion tracts of the crus finds its course interrupted by the 
interpolation of a ffangllon-cell before it reaches the particu- 
lar spinal neive, with the action of which it is to become inti- 
mately associated. The nerve-cells of the spinal cord help to 
explain the various phenomena which are comprised under 
the head of spinal automatism ; since, in the beheaded animal, 
no other source of refiex motor action can be discovered, al- 
though its existence has been demonstrated beyond a doubt, 
both in animals (Pfluger) and even in man (Robin). By the 
interpolation of nerve-cells in the course of nerve-fibers, sen- 
sory impressions may be carried to any one of the three main 
divisions of gray matter, and there excite a response in the 
fonn of a motor impulse, viz., the tubular gray substance 
and its expansions, the basal ganglia, or the cortex of the 
cerebrum. These points will be discussed in subsequent 
pages. 



THE CORTICAL GRAY MATTER. 43 

THE CEREBRAL CORTEX. 

If a section of the cerebral cortex, in a plane vertical to 
that of the surface, be pressed between two thin plates of 
glass and then inspected by transmitted light, it will appear 
to the naked eye to resolve itself into secondary zones^ or 
strata of unequal transparency. 

It is this i)eculiar appearance that has led some anatomists 
to describe the cortex as consisting of regularly stratified lay- 
ers of alternating gray and white matter — ^a statement which 
is not supported by microscopical research. 

The intimate structure of the cortical substance is not the 
same in all parts of the brain. Many valuable suggestions 
are afforded by the variations in this respect which special 
parts present from the type most commonly met with in the 
convolutions. These will be considered later. 

The convolutions of the brain apparently obey some fixed 
law as regards their development, distribution, and the micro- 
scopical characteristics of their cortical layer. 

If the most prominent points of the convolutions in any 
given horizontal or vertical section of the adult brain be 
united by a curved line, it will be found that the curve de- 
scribed is continuous if the brain be in all respects a typical 
one. In old age, effects of senescence become manifest in the 
brain, as in the other organs. One of these is a retraction or 
sinking of certain convolutions, so that a continuous curve no 
longer unites the tips of aU the convolutions over which it is 
described. In addition, the gray matter of the cortex be- 
comes diminished in thickness in old age ; and its color is 
changed to a yellowish white, on account of a transition of 
the cell elements into a granulo-fatty state. In certain men- 
tal diseases, also, which tend to create a premature dotage, 
such as alcoholic poisoning, paralytic dementia, melancholic 
delirium, etc., we are apt to discover an atrophy of the cor- 
tical layer. 

The convolutions of the brain present all varieties of con- 
figuration, not only in animals of different species, but even in 



u 



TEE BRAIX. 



the same individual. Even in homologons regions of the 
brain the convolutions are seldom, if ever, the same in poiat 
of outline. Luys suggests that this can be demonstrated by 
laying a piece of transparent paper over a vertical secdoQ 
of the brain, and tracing upon it the outline of the con vol u- 



iL MA 



Fia. IG. — ikruciure of tht ojia. 



(After Boillarger.) 



1, the %\% altcniAte graj aim) white lajers in the oortical dubsUnoe of the convolutiona ; 
2f enlarged section of n conrolutioii — the left half is seen by reflected light — laye 
ftirmnged as in the preceding figure — iu the Hght half, t^cen b>- tmnfltnlttcd light, d 
medullary layers art? rendered dark by their opaciiy — the layers of gray subetADoe, < 
the other hand, which are inm^looeDt, are repreiiented in white ; 3, s^cthm of ft oo 
▼olution showing the unequal thicknesB of the white layers — at lirst ught onJy thr, 
layers rain be dUiingiii&hed, two gray and an intervening white layer — ^more attenttiii 
examination showt^ ^\x layers, the superficial and deep white layers being, howeve 
very narrow ; 4, icetion of a convolutioa ghowingr the three layers of i;ray matter 
observed by Vie<i d'Azyr in the occipital lobe; 5, tendency to mdlation phown by 
the while fibers in the gray matter of the convolution!*; fi, peetion of a cerehr«d 
mnvnlution lu a newly-bom infant^ w?en by reflcrte! li^jht— it prcsentu a homo^ftir^ 
<ms appeal anue ; 7, «ame soot ion eecn by tranamittoii li^^ht — pi-enentB the saiue Ktimti- 
ficatlon and tendency lo radiation which are observed iu the adtilt 

tions of one side as far as the median line ; now double thji 
papej over so as to cover corresponding regions of the opj 
site aide, and no two convolutions will be found to presei 
an absolutely idpntiral contour. The same ol)!st:*rver 8tat4 
that, in liis extended res«earches, he ha*i never encouDtered 
braiu which was perfectly symmetrical when tested in tl 
way. This statement has a medicodegal value — a^ymviet 



THE CEREBRAL CORTEX, 45 

having been thought by some neurologists to be conclusive 
evidence of existing disease or congenital defect. 

The color of the cortex differs with age and the race. In 
the dark-skinned races, especially marked in the negro, it is 
darker than in the white man ; in the babe, it is uniformly 
grayish, and of a gelatinous consistence ; in early childhood, 
it assumes a somewhat rosy tint ; in the adult, its vascularity 
is apparent ; in old age, it assumes a yellowish white color, 
and loses its vascularity. The gray color of some zones as 
comi)ared with others is stated by Meynert to be due to the 
presence of pigment within the cell elements with which the 
cortex is so abundantly supplied.* 

The thickness of the cortical substance varies in different 
r^ons of the brain, being thicker in the anterior parts, as a 
rule, than in the posterior. Its average thickness may be 
stated to vary from two to three millimetres. Gratiolet has 
called attention to the curious fact that the thickness of the 
cerebral cortex is much less in races of small stature than in 
those of greater average height. 

If we make thin sections of the cortex and color them 
with different reagents (each of which, by its chemical affini- 
ty, tends to bring out some special feature in its anatomical 
construction), and then subject them to the magnifying power 
of strong objectives, we are enabled to form a clearer concep- 
tion of the actual construction of the zones of unequal trans- 
parency seen by the naked eye (first brought to professional 
notice by Baillarger) (Fig. 16). By the judicious employment 
of gradually increasing powers in the microscopic objectives 
used, the general arrangement of the elements may be first 
mastered, and, later on, the minute details of each of the com- 
X)onent parts may be studied. 

In such research we are struck, at first, by the immense 
numbers of pyramidal'Shaped cells^ which are encountered 

' We know that the medullary Fubstance of the *' island of Roil " and of the ** exter- 
nal oapaule" is here and there studded thickly with nerve-cells, whichf howoyer,/at/ to 
fkH U a gray appearance on account of the abi^^ncc of pigment. 

' Meynert pronounces the ncnre-ccUs of the outer cortical layer to be distinctly star- 
', but others disagree with him. 
6 



4r. 



THE BEAL\ 



within the cortical substance, each of which seems to 
toward the surface of the brain ; as if attracted toward it, 
needles *'ao magnetized as to always point to the pok 



A^ 



r/y 



4^ 



\ 
Fio. 17. — Cortkat ccfl of I he deeper tone* ai ahovi eipfU humlrtd diamctm. 

A section of the cell is made through its groater axifl^ t^ interior texture being thusQ 
bare. A rcproecnU the superior prolongation mtitating from the nmss of the n^ 
cleus iti^clf ; B, latenil and poatoriur pix^longaiion^ ; C^ dfxmgy areolar ^iibstiuice, 
into which the structure of the c*-H itself is resolved ; D, the nucleus iUclf ^*ei!n» 
only to be a thiekt'Dvag of thifi areolar Mtromai— it sometimes lias a radiiUijti arrange 
ii»;nt ; E^ the bdght nudeohis is iteelf ilc<M>nipoeMibk* into i^econdarr tilann"nt«. 

These are the nerve-cell^. They are, furthermore, disposed 
regular strata^ parallel with the surface of the convolutions 
and i)laced successively upon each other. It will be noticet 
in the third place, that the celU ffrow larger as you pass froi 
the external strata inward;* and that those of each individ- 
ual layer have some distinctive peculiarities which appear U 
shed some light upon their function. When we come 

> Th«y van* from 10 ^ lo 40 ja In lieighw 



THE CORTICAL CELLS. 47 

study the characteristics of the different layers, these points 
will be discussed. Our attention is drawn, in the fourth 
place, to the fact that these cells give off hranching processes 
which anastomose with each other, thus constituting what 
may be considered a continuous structure over the whole area 
of the convolutions. By means of these small, thread-like 
processes, the cells are probably enabled to communicate 
vibratory molecular movements from one to the other, while 
some are the unquestioned means also of communication be- 
tween the nerve-cells and the nerve-fibers which we have pre- 
viously discussed. In the fifth place, we encounter an inter- 
ceUvZar sttbstance^ which serves to cement the cells and to 
maintain a fixed position for them, as well as to furnish pas- 
sage for the vessels of nutrition of the cells. This is the 
"neuroglia," a connective-tissue formation. 

We are now enabled to appreciate the analogy which Mal- 
pighi drew between the arrangement of the cells of the cortex 
and the seeds of the pomegranate, imbedded in the white 
fibrous tissue which incloses them on all sides. 

The nerve-fibers probably join the nerve-cells in the region 
of their bases ; Ihe processes given off from the apices of the 
cells appear to serve as a means of communication between 
the cells of the different layers of the cortex. 

The nerve-cells^ when examined as individual structures, 
are found to present a bright nucleus* and a nucleolus, and 
to be destitute of an investing membrane (Luys). In fresh 
brains, they are of an ambpr color. When very high powers 
are used, the protoplasm of the nerve-cells becomes resolved 
into distinct fibrillse, which interlace with each other and 
become agglomerated in the region of the nucleus. The ar- 
rangement of these delicate fibriUffi has been compared by one 
of the most recent investigators (Luys) to the ''wickerwork 
of an osier basket," and the same observer claims that the 

I In jonng cubjects and in nortnal adult brains, the nucfei are aeidom round or oral 
Thej are uaiiftlly pyramidal or npind/e-nhapedy running out into sharp ends. Their anprlcs 
are often seen to project into the celUprooeMcs. Arnold states that the pressure of the 
proloplatm of the cell tends to niake the outline of the nucleus correspond to that of the 
oelL 



48 



TffE BRAIN, 



micleas and nucleolus have been resolved t>y i 
tinct secondary filaments which present a radiated aj) 
anoa I quote from him as follows: *^ Imagination is con 
founded when we penetrate into this world of the infiniteJ]| 
little, where we find the same infinite divisions of matter thfl 
so vividly impress us in the study of the mdereal world ; and 
when we thus behold the mysterious details of the orgunii 
tion of an anatomical element,, which only reveal tliemselTi^ 
when magnified from seven to eight hundred diuniet4?r», an^ 
think that this same anatomical element repeats itself 
thousand fold throughout the whole thickness of the c?er 
bral cortex, we can not help being seized with admiration; 
especially w^hen we think that each of these little organs 
has its anatomy, its individuality, its minute organic sensi^ 
bility; that it is united wth its feHows; that it partici- 
pates in the common life; and that, above all it is a silent 
and indefatigable worker, discreetly elaborating those nerv- 
ous ff*rces of the psychic activity which are incessantly ex-l 
pended in all directions and in the most varied manners.! 
according to the different calls which are made npon it and 
set it vibrating." 

The neuroglia^ to which we have referred in a general wayl 
as serving as a cement to fix the nerve-ceUs, allows also of thai 
transmission of blood-vessels into the substance of the cortex,! 
The branches given off from the vessels of the jjia mater entei 
the cortex upon its free surface, and immediately divide intol 
a network of small capilliiry twigs, which invest the adjacent 
nerve-cells in an ai^ola extremely rich in blood-vesaels. lxk\ 
addition to these two functionsj the most sui>erficial layer of 
the cortex is composed largely of this connective- tissue forma- ^ 
tion, as will be seen by studying tlie diagrammatic drawing™ 
which I now show yon. 

This stratum of the cortex has been compared by Luyal 
to the epithelial covering of the mucous and cutaneous snr- 
faces of the body, since he believes thxit it is designed toj 
protect the nerve-cells from direct contact with the capillariea] 
of the pia mater. 



» 



AThile serving thus as a source of protection and isiAi 
it prolwbly also Hirers, as it were, the juices which escaj 
ftx)m the meningeal vessels for the noiirishHient of the nervouj 
elements. This view seems to be supported by a peculiarity 
in the arrangement of the smaller vessels, which can be traced 
into the substance of the cortex^ They are found to be stir 
rounded for almost their entire circumference by an adventi- 
tious sheath, which ^4nvests them like a muff,** and prevents 
the nerve-cells fr<jm coming into direct contact with any jjor- 
tion of the vascular system. We are forced, therefort*^ tu 
believe that the nerve-cells derive their nutritive elements 
only through the mediation of other structures. The external 
layer of the cortex \n\\ subsequently be considered in det4til. 

We are prepared now to take up the special types of 
cortex which are met with ; and to study the hints which are 
thus afforded respecting the functions of various parts. By 
the laws of analogy, we are led to infer that parts which have 
a simUarity of construction, and in which the cell-elements 
are absolutely identical, proliably have a similarity of func- 
tion. If, on the other hand, the function of certain regions 
has, by physiological experiment, been clearly made out, we 
are led to study closely the minute structure of those special 
regions, with the hope of linding other localities where iden- 
tical formations exists 

The superficial layer of the cortex has been described by 
Vtrchow as ^''t\m neuroglia''; by KuUiker as ** connective 
tissue"; by Deiters as ** spongy tissue*'; by Rokitansky as 
**ependyraa"; and by Wagner and Henle as *' fused gan- 
glion-cell substance.'- Similar tissue found in the olfactory 
lobes and Amnion's horn has lieen named ** gelatinous sub* 
stance"' by Clarke, and *' molecular substance*- by KupfeK 
Hence, we must be prepared to meet descriptions of this layer 
under the above-mentioned headings. This stratum varies 
perceptibly in thickness in different mammals, and, as Mey- 
nert expresses it, seems to be overbalanced and thrown in the 
shade by the deeper nerve-cell ladened strata in the nobler 
tyi)es of brains. We find it relatively thin in the brain of 



SPECIAL TYPES OF CORTEX, 61 

man and the monkey, thicker in the dog and cat, and thickest 
(of all the domestic animals) in the calf. The cells found in 
this layer are chiefly star- shaped (Meynert),* have very little 
protoplasm, and possess many finely divided processes. These 
are probably non-nervous in function. A few nerve-cells are 
found, however, which are characterized by an excess of pro- 
toplasm (Deiters) and forked processes ; and some nerve-fibers 
may be also detected in this layer (Amdt) in the region of the 
surface, which interlace in all directions. In the ''gyrus un- 
cinatus " this medullary layer is developed to a high degree. 

In the majority of the convolutions of the cerebrum the 
cortex may be subdivided into five strata. The structural 
differences in the four strata, underlying the one already con- 
sidered, consist in variations (1) in the relative density of 
distribution, and (2) in the form of the nerve-cells. 

As regards the form, that of the pyramid (the only one 
recognized by Amdt, Luys, Stephany, and others) prevails 
in the five-strata type of cortex. 

In the second stratum, the cell elements are of small size 
and closely packed together ; in the thirds they are of larger 
size, gradually increasing both in size and distance from each 
other as you pass inward from the more superficial portion 
(the type peculiarly indicative of AmTnorCs horn) ; in the 
fourth^ Meynert describes closely packed cells of small size 
(granule-like formation) ; in tlie Jifth^ the same author claims 
to detect spindle-shai)ed cells," which he considers as particu- 
larly characteristic of the gray matter of the claustrum. The 
fifth layer of the cerebral cortex is subdivided by Lewis, 
Clarke, and Baillarger into two layers, thus making six 
layers. Krause has added a seventh layer, which he de- 
scribes as being composed of very small cells lying upon the 
white substance of the centrum ovale. These cells, according 
to this author, may be pyramidal, stellate, or fusiform. 

' OeHen recognizes only free nuclei in this layer. They incaflurc about 10 ^ in 
diameter, tooording to this observer. 

* TIm ^^fUuBeshaped celU are not bipolar. Procc8f»c8 can usually be detected which 
•prinf from their fides as well as from their extremities. 



SPECIAL TYPES OF CORTEX. 53 

Considerable variety occurs in different parts of the cere- 
bral cortex in regard to the size and shape of the nerve-cells, 
and the relative thickness of the layers. 

It is especially worthy of notice that, in those regions of 
the cortex which have lately been shown to contain the motor 
centers^ the deeper pyramidal cells have been found by Betz 
to be very large, and arranged in clusters or nests of four or 
five cells, which are more or less defined. These are often 
called the ^' giant cells. ^^ They bear a strong resemblance to 
the large motor cells found in the anterior horns of the gray 
matter of the spinal cord. 

Bevan Lewis and Clarke have paid special attention to the 
situation of these peculiar cells, and have arrived at the con- 
clusion that they are chiefiy found among the small cells of 
the fourth layer of the cortex. The same observers have 
applied the name of ''ganglionic cells ^^ to these peculiar 
elements, which apparently have an intimate relation with 
the function of muscular movement, and have designated the 
layer of the cortex in which they are found as the "ganglionic 
layer. '* 

In the neighborhood of the calcarine fissure large cells 
in the cortex are very scanty, their place being occupied by 
those of small size. In some parts of the cortex six layers 
may be discovered ; this is due, as shown by Bevan Lewis, 
to an insertion of an additional layer of small cells between 
the third and fourth layers. The claustrum^ hippocampus 
major or cornu Ammonis^ and the olfactory lobe present 
especially characteristic variations of the cortex from the 
more common five-strata type shown in the diagram ; but 
space will not admit of a minute description of the peculiari- 
ties of each.* It may be stated, however, that the study of 

' The researches of Beran Lewis and IT. Clarke in reference to the minute Btructiire 
of the ocrebral cortex in man and animals were published in the ** Proceedings of the 
Bojal Society** in 1878. The former author has also contributed articles to the "Philo- 
flophlcal Transactions** for 1880 and 1882. Mevnert*s valuable article is to be found in 
Strieker's work on Histology. 

The most remarkable deviations from the normal five-strata tjpe of cortex are to bo 
found in the incurved portion of the cerebral hemisphere in the region of the hippo- 
OtmiMis major (wrMk Ammon%i\ and in the olfactory lobe. Ilenle gives cuts showing 



54 THE BEAiy. 

the cortical elements has afforded grounds for many attractive 
theories regarding the functions of sx)ecial regions of the 
brain, and has also confirmed an opinion (previously formed 
by research in embryology and comparative anatomy) that 
the olfactory lobes and tracts are component parts of the 
brain, and are not to be classed among the cranial nerves. 
Luys has contrasted some points in the structure of the olfac- 
tory bulbs with those of the retinae; and the same author 
dmws a strong analogy between these two organs of special 
sense and abridged projection systems. 

From what has already been stated in regard to the ana- 
tomical construction of the cortex of the cerebrum, it seems 
logical to assume that each zone may be thrown into a state 
of nervous activity independently of the others^ because the 
structure of the cells differs in the various strata. On the 
other hand, the connecting processes of the cell elements 
which unite the superimposed strata would seem to indicate 
tliat the various zones of the cortex may he associated in 
their action under certain conditions, and that the effects of 
nervous vibmtions within the cells are in some way modified, 
according to the nature of the intermediate cells brought 
into play. 

Nervous actions, like vibmtory undulations, are probably 
transmitted within the cortical substance both horizontally, 
along some si)ecial stratum, and vertically from the super- 
ficial to the deeper cells, or rice versa. 

It is worthy of notice that in the 2^osterior horns of the 
gray matter of the spinal cord we find cells of small size 
which are analogous in many respects to those of the second 
layer of the cortex ; while in the anterior horns large cells 
predominate as they do in the third stratum. 

Morphological analogy would seem to indicate identical 
function. Luys advances the theory that the sub-meningeal 
strata which are characterized by the presence of cells of 

excellent sections of both of these regions. The articles referred to above will furnish 
the reader with a complete description of the peculiarities of structure which are char- 
acteristic of each. 



FUNCTIONS OF CEREBRAL CORTEX. 55 

small size are to be considered as the areas of diffusion of 
general and special sensations ; and that the deeper strata, 
characterized by the presence of large cells, are the centers 
for the development and emission of motor impulses. 

There is certainly some ground for a theory that the cor- 
tex may be regarded, from a physiological standpoint, as an 
*' extensive instrument possessing a sensory-motor function''; 
analogous, in many respects, to the gray matter of the spinal 
cord, but endowed with special attributes of a higher order 
(consciousness, volition, memory, etc.). 

We are inevitably forced to the conclusion that the cere- 
bral cortex must be regarded as the chief, if not the exclusive, 
seat of mental activity. The essential proofs of the psychical 
function are as follows : 

1. In the animal series, the cerebrum seems to be devel- 
oped in excess of other parts of the brain in proportion as 
the individuals of any class approach the standard of man in 
mental powers. We judge of this by its weight, and also by 
the number of *' convolutions," or '^gyri." The latter serve 
to increase the amount of gray matter in proportion to the 
superficial area of the brain. 

2. In cases where the cerebrum is extremely small from 
birth, there api)ears to be a corresponding diminution in the 
higher mental faculties, or idiocy exists. 

8. Some forms of mental disturbance almost always follow 
injuries, compression, and diseases of the cerebrum — as evi- 
denced by insensibility, somnolence, abnormal excitement, or 
some marked eccentricities of demeanor. 

4. Experimental physiology has shown that a removal of 
the cerebral hemispheres in the bird (in which animal it is 
easily accomplished) produces a stupor resembling sleep, in 
which all volurdary acts cease. Plourens noticed that a 
removal of the cerebrum in thin slices tends toward a gradual 
loss of mental power. Animals so mutilated are capable, 
however, of movements of a reflex character when any of the 
organs of sense are subjected to stimulation ; but they are so 
regular in the order of their occurrence tliat they may be 



56 THE B£Aiy. 

predicted, thus proving that they are not the result of voli- 
tion on the part of the bird itself. Foster, in his work on 
physiology, gives an interesting and concise account and 
summary of similar experiments made upon other animals. 
Most observers, however, have arrived at about the same 
conclusions, so it is unnecessary to enter into detail here as 
to the results of the experiments made by each. 

Now, from what has been already stated in this and a 
previous article, we can construct a general scheme of the 
nervous system as follows : 

1. The central gray matter of the spinal cord. This has 
no connection with the higher senses. It is capable, in itself, 
of the simplest kinds of reflex acts, by means of the spinal 
nerves. These can be produced, at the will of the experi- 
menter, in the beheaded frog, when an irritation of the skin 
by any acid, etc., is created; and Robin has satisfactorily 
performed the same experiment upon a beheaded criminaL 
We have reason to believe that the spinal cord can be slowly 
and in a purely automatic way taught to perform certain 
series of muscular movements (as in playing scales upon a 
musical instrument, for example) without any intervention of 
the hiij^her ganglia. 

2. The hasal gnnglia^ and possibly the cerebellum. These 
are of a higher ordt^r in ])oint of construction than the spinal 
gray matter. They are connected directly or indirectly with 
the nerves of the spinal (M)r(l, and, in addition, with those of 
the special senses. They are (;ai)al)le, in themselves, of exe- 
cuting more complex actions, besides those of a purely reflex 
type, in obedience to impressions received from the nerves of 
special sense, as well as from the spinal nerves. These gan- 
glia are probably important agents in guiding muscular move- 
ments in response to visual impressi(ms and those from the 
sense of hearing. In this way, they seem to have an impor- 
tant control over the maintenance of equilibrium (co-ordinated 
movement). 

3. The cerebral cortex. This is a ganglion of the highest 
order ; in which the mental activities are seated, in addition 



TOPOGRAPHY OF CEREBRAL CORTEX, 57 

tb the function of elaborating and storing of sensory impres- 
sions of all kinds, and transforming them, at the proper time, 
into appropriate motor impulses. Here we encounter *'the 
mysterious realms where the living forces of our psychic 
activities are marshaled and organized"; where volition has 
its seat, giving to the physical organization its individuality ; 
and ** where those eternal problems respecting the relations 
of our corporeal and mental being are solved and carried into 
execution." 

TOPOGRAPHY OF THE CEREBRAL CORTEX. 

We are indebted to the admirable monograph of Ecker 
for a systematic grouping of the convolutions, or "gyri," 
which will materially assist us in studying the peculiarities 
of formation of each, and especially in defining special 
centers whose functions seem to have been determined by 
experimental physiology. Many of the terms employed 
by this author and some of his predecessors are now em- 
bodied in most of the recent works on physiology and 
descriptive anatomy, although there are structural grounds 
(pointed out by Meynert) which make them appear some- 
what illogical. 

We may simplify the study of this subject by first 
enumerating four lobes, four lobules, and eight fissures, 
which are prominent upon the exterior surface of the cere- 
brum. These are as follows : 



Tbk four lobes ari: 



The rouR lobules ire: 



The noBT fissures are: 



The frontal lobe. 

The parietal lobe. 

The temporo-sphenoidal lobe. 

The occipital lobe. 

The lobulus centralis (the i^^land of Reil). 

The lobulus paracen trails. 

The lobulus cuneus. 

The lobulus quadratus. 

Ascending limb of the fissure of SvItIus. 

Horizontal limb of the fissure of Sylvius. 

The fissure of Rolando. 

The external parieto-occlpital fist^ure. 

The transTcrse fissure. 

The hippocampal or dentate fissure. 

The calloso-maniinal fissure. 

The calcarine fissure. 



58 THE BRAIN. 

The Principal Fissures of the Cerebrum. — By refer- 
ence to Figs. 20 and 21, the following points of interest may 
be noted in this connection : 

The ascending limb of t\iQ fissure of Sylvius (*") passes in 
front of the island of Reil and among the frontal convolutions. 

The horizontal limb of the fissure of Sylvius (s') passes 
backward behind the island of Reil, and separates the tern- 
poro-sphenoidal lobe from the frontal and parietal lobes, 
which lie adjoining it. 

The fissure of Sylvius has a surgical and medical impor- 
tance from the fact that it contains the middle cerebral 
artery. This vessel is particularly liable to obstruction from 
the impaction of an embolus, especially upon the left side of 
the body. This accident is commonly followed by aphasia, be- 
cause the motor centers of speech are supplied by this artery. 

The fissure of Sylvius appears at about the fourth month 
of fcDtal life. The fissure of Rolando api)ear8 at about the 
sixth month, and is determined, according to the investiga- 
tions of Krause, by a vein tliat joins the superior longitudinal 
sinus with the middle cerebral vein. 

The fis.sf/re of Rolando (r) separates the frontal from the 
parietal lobe ; it passes downward and forward from the 
upper part of the cerebrum till it almost joins the horizontal 
limb of the Sylvian fissure. 

The external parieto-occipital fissure (po) separates the 
parietal and occipital lobes, hence its name. It is continued 
upon the inner surface of the cerebrum as the *' internal 
parieto-occipital fissure." It is very variable in its extent, 
and is sometimes scarcely recognizable. 

Amcmg the minor fissures of the cerebrum that deserve 
mention may be enumerated the transverse, hippocami)al, 
olfactory, collateral, calloso marginal, and calcarine. 

The transverse fissure (fissure of Bichat) separates the 
cerebrum from the cerebellum when those ganglia are in their 
normal relations to each other. It is continuous with the 
lateml and third ventricles. Here the pia mater enters the 
ventricles of the cerebrum. 



TOPOGRAPHY OF CEREBRAL CORTEX. 



59 



The hippocampal fissure (dentate fissure) is seen upon the 
internal surface of the cerebral hemisphere, and indicates the 
seat of a convolution in the descending comu of the lateral 
ventricle, known as the '* hippocampus major." 




_ 02 



Fio. 20. — Lateral view of the human brain, ihowing its lobes and fissures. (After Ferrier.) 

F, frontal lobe ; P, parietal lobe ; 0, occipital lobe ; T, temporo-spbcnoidal lobe ; S, fis- 
Bore of Sylvius; S', borizontal portion ; S", ascending portion of the same; c, sulcus 
centralis or fissure of Rolando ; A, anterior central convolution or ascending frontal ; 
B, poaterior central convolution or ascending parietal; Fi, superior; Fs, middle; 
Ft, inferior frontal convolution ; f i, superior ; t%, inferior frontal sulcus ; f i, sulcus 
prsDcentralis ; Pi, superior parietal lobule, or postero-parietal lobule; Ps, inferior 
parietal lobule, viz.: Pt, gyrus supra-marginalis ; Pa', gyrus angularis; p, sulcus 
inira-parietalis ; cm, termination of the calloso-marginal fissure ; Oi first, O9 sec- 
ond, 0i third oodpital convolutions ; po, parieto-occipital fissure ; o, sulcus occipi- 
talis transvcrsus ; Ot, sulctis occipitalis longitudinalis inferior ; Ti first, T9 second, 
T| third temporo-sphenoidal convolutions; ti first, tt second temporo-sphenoidal 
flMores. 



The olfactory fissure lodges the olfactory bulb. It is seen 
on the basal asi)ect of the cerebral hemisphere. 

The collateral fissure is seen cm the basal aspect of the 
occipital and temporal lobe, ending at a point opposite the 
hippocampal fissure. It corresponds to the seat of the so- 



60 THE BEAIN. 

called ^^ collateral eminence" in the descending coma of the 
lateral ventricle. 

The calloso-marginal fissure (Fig. 21) mns parallel with 
the corpus callosum. It joins the fissore of Rolando at its 
upper extremity. 

The calcarine fissure marks the projection of the hippo- 
campus minor (calcar acts) into the posterior horn of the 
lateral ventricle. It joins the internal parieto-occipital fissure 
(Fig. 21). 

TuE Lobes of the Cerebrum.— These are designated by 
the bones with which they bear relation ; hence their names 
will serve to indicate in a general way their situation and 
extent. 

The main sulci, or fissures, are the dividing lines between 
the lobes; the smaller sulci seen in the diagram (Pig. 20) 
separate the different convolutions, or ''gyri" 

Upon the internal surface of the cerebrum, hidden from 
view by the contact of the hemispheres unless they be pulled 
apart, are three fissures, which have been designated as the 
'* caUoso7narginaI^^' the ''infernal parieto-occipitaZy^ and 
the ^^ calcariney These will be seen in the cut now indi- 
cated (see Fig. 21V 

The FROXTAL LOBE (F iu Fig. 2i>) is contained within the 
anterior fi>ssa of the skull. The frontal lobe of the human 
adult brain includes ne;u'ly the anterior half of the cerebral 
hemisphere. Only that portion that lies in front of the as- 
cending frontal convolution is contained within the anterior 
fossa of the cniniuni. This parr has l>een named the " pre- 
frontal lobe " by some physiologists. The frontal lobe pre- 
sents four ''gyri/' which are si>ecially named. These are 
shown in Fig. 20 to be as follows : 

The ascending frontal conrolution. or gyrus (A), which 
lies anterior to the fissure of Rolando, being separated from 
the ascending jxirietal convolution by that fissure. 

The suptrior frontal conrohttion^ or gyrus ^Fi*, "which 
joins the asi^ending gyms, passing horizontally across the 
frontal lol^e. 



THE CEREBRAL CONVOLUTIONS. 



61 



The middle frontal convolution^ or gyrus (F,), passing 
parallel to the superior. 

The inferior frontal convolution^ or gyrus (F,), lying be- 
low the middle, embracing the ascending limb of the fissure 
of Sylvius. 

Benedikt has observed the frequent occurrence of ^fourth 
frontal convolution in the brains of criminals. It was found 
to exist, more or less completely developed, in the majority 
of brains of this class to which he had obtained access. It 
originated usually by a bifurcation of the middle frontal con- 




Ffeo. 21.—^ dioffrtun of the cerebrum in hnffiiudinal median teetion, (After Dalton.) 

1, cmUoto-marginal fissure ; 2, parieto-oodpital fissure ; S, calcarine fissure ; A, third ven- 
tricle ; By fifth ventricle ; D, anterior crura of fornix ; G, cuneus (occipital lobule) ; 
Q, pnecuneus (lobulus quadratus) ; P, para-central lobe ; G G, corpus callosum ; 
F, Qrrus fomicatus. 

▼olation, occasionally by a bifurcation of the superior frontal 
convolution. Other points of interest are presented, includ- 
ing the occurrence of a Jifth convolution. These facts the 
author regards as the expression of a great pathological law, 
that atypical structure is the chief agent in thie production of 
atypical (morbid) performance of function. 

The PARIETAL LOBE (P) has also four convolutions, or gyri, 
called the ascending, the supra-marginal, the parietal lobule, 
and the angular gyrus. The parietal lobe is slightly over- 
lapped by the occipital bone, so that it does not correspond 
exactly to the parietal area of the skull. Its convolutions are 




The ascending parietal convolution (B in Fig. 20) lias back 
of the fissure of Rolando, being separated from the ascendii] 
frontnl convolution by raeans of that fissure. 

The parietal lobule (P,), the supra-marginal canvoluii^^i 
(PJ, and the angular gyrus (P,'), being the other three cob 
Tolutions of the parietal lobe, are situated behind the aBoend-| 
ing parietal convolution* 

The supra-marginal convolution is named from it8 rela 
tion to the fissure of Sylvius. It lies above the horizonti] 
limb of that fissure, and embraces its terminal extremity. 
The {tjferior parietal lobule lies between the supra-niargii 
gyrus and the so-called intra- parietal fissure. This fissur 
separates it from the superior parietal lobule^ which lies 
jacent to the longitudinal fissure. 

The convt>lutions of the parietal lobe are connected U) cer 
tain adjacent convolutions by so-called '* annectani gyri. 
Thus, the superior parietal convolution is joined to the oceipi-l 
tal lobe by the first annectant convolution^ and the angular 
gyrtis is connected to the occipital lobe by two or three an^fl 
nectant bands. " 

The TEMPORo-sPHENoiDAL LOBE (T in Fig. 20) presents 
three well-marked convolutions, which ran in an antero-j 
tenor direction. They are named as follows : 

The superior temporo'Sp7tenoid<d conrolution (T,), which ' 
lies below the horizontal limb of the Sylvian fissure^ and 
which is continuous behind with the parietal lobe. 

The middle temporO'Sphenoidal convolution (TJ, which 
becomes continuous with the angular gyrus, and is connected 
to the middle occipital convolution. 

The inferior ternporo sphenoidal convolution (T,), seen on 
the under surface of the cerebrum, and connected with the 
thii*d occipital convolution. 

Tlie superior temporal convolution (T,) is often callc 
the inframarginal gyrus. The tenn suhicular region^ 
the legion of the subicutum c&rnu anunanis (sigmoid cohto- 



hi«^h^ 



the 
led! 

J 



CEREBRAL CONVOLUTIONS. 



63 



lution of the horn), is applied to the tip of the temporo-sphe- 
noidal lobe. 

The OCCIPITAL LOBE (0 in Fig. 20) presents three badly de- 
fined convolutions, which are superimposed upon one anoth- 
er, and which lie in a more or less antero-posterior direction. 

The superior occipital convolution (O,) is connected with 
the parietal lobule. 

R 




Fio. 82. — A diagrammatie figure^ showing the cerebral eomvotiUions. (Dalton.) 

S, fisrare of SjWiuB, with its two branches, a and 6, 6, h ; R, fissure of Rolando ; P, 
parieto-ocdpital fissure; 1, 1, 1, the first or superior frontal convolution ; 2, 2, 2, % 
the second or middle frontal convolution ; 3, 3, 3, the third frontal convolution, curv- 
ing around the ascending limb of the fissure of Sylvius {motor anter of speech)^ 
4, 4, 4, ascending frontal (anterior central) convolution ; 6, 6, 6, asot-ndiiig parietal 
(posterior oentnd) convolution ; 6, 6, 6, supra-Sylvian convolution (parietal lobule), 
which is continuous with 7, 7, 7, the first or superior temporal convDlution; 8, 8, 8, 
the angular convolution (or CTrus), which becomes continuous with 9, 9, 9, the middle 
temporal convolution; 10, the third or inferior temporal convolution; 11,11, the 
superior parietal convolution; 12, 12, 12, the superior, middle, and inferior occipital 
oonvolations (called also the first, second, and third). It is to be romembercd that 
the term "pgrrus" is sjmonymous with "convolution," and that both terms are often 
iDtercbaoged. 



The middle occipital convolution (O,) is connected with the 
angular gyrus, and also with the middle temporo-sphenoidal 
convolution. 



64 



TEE BRAIN. 



The inferior occipital convolvtion (O,) is connected witi 
the inferior temporo-sphenoidal convolution. 

The admirable diagram (Fig. 22) to which I now call your 
attention shows the relative position of the gyri, as well as 
their extent, configuration, and lines of continnation into 
neighboring convolutions. While it is more schematic than 
that of Ferrier, it is better* adapted for the purposes of in- 
struction. In its general outline, however, it resembles the 
brain of the monkey, rather than of man, as the frontal lobes 
are small, and the fissure of Rolando somewhat far forward. 

The LOBULES of the cerebrum (enumerated on a preceding 
page) demand individual mention. One of them (the lobulus 
centralis) lies at the base of the frontal lobe ; the other three 
are found upon the internal surface of the cerebrum. 

The lobulus centralis^ or island of Reil {instUa\ lies 
deeply situated in the commencement of the fissure of Syl- 




Fio. ^X—Orhttnf surf ace, of the frontal lobe and Island of Beil. (Tiimer.) 

The Island of Reil is exposed by renioval of the tip of the temporo-sphenoidal lobe ; 
TS.f cut edj^e of this lobe ; a. p. *., anterior perforated space ; a,a, Ji^ p. «. /?., ante- 
rior and posterior limiting? sulci of the island; o/>., operculum; tr. *., tri-radiate sul- 
cus ; I, o. c, a. o. c, and p. o. r,, internal, anterior, and posterior orbital convolutions; 
olf »., end of olfactory sulcus ; o//'. /r., olfactory tract, bifurcating into the inner and 
outer roots ; m, middle root, or tuber olfactorium. 



LOBULES OF THE CEREBRUM. 65 

vins. It can be made visible only by the separation of the 
lips of that fissure or the lifting of the operculum (see Fig. 
23); hence it lies in intimate relation with the "basal gan- 
glia.'* It is a triangular eminence, and consists of five or six 
straight convolutions {gyri operti)^ which radiate outward 
from a i)oint just external to the anterior perforated space. 
It covers the lenticular nucleus of the corpus striatum. The 
drawing to which I now call attention shows the appearance 
of this lobule after the end of the temporo-sphenoidal lobe 
has been removed. The discovery of Broca that this region 
contains the center for the movements necessary to articulate 
speech (a statement which clinical experience has not yet been 
able to overthrow) has given it a clinical and physiological 
importance in excess of other convolutions. 

Marshall has called attention to the fact that the island of 
Reil is imperfectly developed in idiots, as are also the corpus 
striatum and the flocculus. In some cases the convolutions 
of the island of Reil were found to be entirely absent. 

The paracentral lobule (P in Fig. 21) is found on the in- 
ternal surface of the cerebrum, in front of the lobulus cu- 
neus. There is clinical evidence to sustain the belief that 
this lobule is connected with the motor tract. We know, 
also, that disease of this convolution produces a secondary de- 
generation of nerve fibers which can be traced through the 
cerebrum along the motor tract and into the motor regions of 
the spinal cord. The '* giant cells" of Betz are also found in 
its cortical layer. 

The paracentral lobule lies in the region of the mesial or 
upper extremity of the fissure of Rolando. It probably pre- 
sides over movements of the big toe (Horsley). 

The lobuhis quadratus (Q) lies between the paracentral 
lobule and the lobulus cuneus, as shown in this drawing (Fig. 
21). It is bounded by the internal parietooccipital and the 
oalloso-marginal fissures. 

The lobuliLS cuneus (C) lies i)osteriorly to the lobulus 
quadratus. Like the preceding lobule, it is inclosed l)etween 
two fissures, the internal parieto-occipital and the calcarine. 



6(5 



THE BRAiy. 



The calcarine fissure carresponds in positio^t^tf 
of the socalled hippocampus miDor (calrar avis), <^o tlie 
of the posterior cornu of the lateral ventricle. 

The marginal convolution (gyrus fomicatas) follows the 
curve of the corpus callosum to a point opposite its free pos- 
terior border, where it terminates in the hippocampal convo- 
lution. Meynert believes that its anterior extremity rai^e 
traced to the olfactory sulcus, ^^^ 

The hipimcampal convolution (superior parietooccipital 
gyrus or uncinate gyrus) is fonned by the union of the mar- 
ginal convolution (gyms fornicatus) and the occipito-teiiii>and 
convolutions of the internal aspect of the hemisphere. It can 
be traced to the tip of the teraporo-sphenoidal lobe, where 
ends in a hook-like bend, called the ''uncus." 

The sO'Called dentate convolution (fascia dentata) b^nSj 
at the posterior extremity of the corpus callosum and ends ; 
the uncus. 

Peduncular Fibers of the Cerebrum. —By means 
the *' peduncular" or ''radiating fibers" of the eei^bmii 
(Fig. 8), the cortex is enabled to receive impressions of thi 
external world and to transmit motor impulses to the inii9-| 
cles» The larger part of these fibers (as stated in a previous 
article) are capable of being traced into the cms and spinal 
cord, but it must be remembered that some also are inti- 
mately connected with the cranial nerves, especially those 
associated with the special senses of smell, sight, and audi^ 
tion. It may not be considered a repetition of pmvious mat 
ter to introduce at this time another diagmm, which will make 
some additions to the facts already recorded. 

Many points shown in this diagram are already familiar 
to you, but a few remain which desen^e mention. One bundle, 
the ** stria cornea," is shown in the drawing. These fibers ran 
from the cortex of the temporal lobe of the cerebnim to the 
caudate nucleus of the corpus striatum, and appear on the 
floor of the lateral ventricle as a curved band, the ** taenia 
seniicircularis.'* The optic thalamus is shown to receive fibers 
which spring from the frontal lobe, passing between the cau- 



PEDUNCULAR FIBERS OF CEREBRUM. 



67 



date and lenticular nuclei of the corpus striatum, and desig- 
nated in the diagram as {a) ; also fibers from the temporal 
lobe, the walls of the fissure of Sylvius, the gyrus fomicatus, 
and the optic tracts. The so-called "geniculate bodies" are 



en 



cm 




rr 






Fio. 24. — A dioffrwn of the fben of a lateral half of the eerthrum, (Fosiar'B 
"Physiology.'* Reichart's edition.) 

CCfft ooitez of the cerebral hemisphere, the convolutions of which are seen to be con- 
nected bj arcuate connecting fibers ; Cb, cortex of cerebellum ; CR^ corona radiata, 
consisting of fibers extending from the cortex cerebri to LN and CN, the " lenticu- 
lar '* and " caudate " nuclei of the corpus striatum, and to OT^ the optic thalamus. 
The posterior extremity of the optic thalamus presents two enlargements, the 
** oorpuB geniculatum externum " and ** internum,** which are seen to be connected 
with the optic tracts. The letters Op, Tr. are placed on a band of fibers that are 
believed to run directly from the cortex cerebri to the cortex cerebelli. SC, " stria 
cornea,** or " tienia semidrcularis *' ; MN, *' red nucleus of the tegmentum ** ; A\ 
** nates**; 7*, '* testis**; P, "pineal gland**; 6, fibers passing directly into the teg- 
mentum from the cortex cerebri ; PaC, the band of fibers to the right of these let- 
ters are part of the " superior peduncle of the cerebellum.** The olfactory nerve 
(o), the optic nerve (Op. TV.), uid the trigeminus or fifth nerve are also shown to 
possess an intimate connection with the basal ganglia and probably with the cortex 
cerebri. A special band of fibers (Op. TV.) are supposed to run from the cortex 
cerebri to the cerebellum. 

also shown to be connected with certain bundles of radiat- 
ing fibers. The bundles which compose the "crusta" and 
'* tegmentum cruris" are made more apparent than in the 
diagram previously drawn. Finally, the fibers connecting 
the cortex of the cerebellum with the testis are clearly 
depicted. 



THE BRAiy. 



FrxcnoNS of the cortex of the cerebrol 

At the present day we are in possession of a saffident 
number of facts, derived from clinical observation, patho- 
logical research, and exj^erimental inrestigatioii, to render it 
certain that no intelligence can exist without brain substance ; 
that the destruction of brain substance imiKiirs intellectaal 
jx^wer ; and that the normal use of the brain implies a d^en- 
eration of its substance and a constant process of r^enera- 
tion, as exists in all tissues. 

It was formerly supposed that the cerebmm was destitute 
of both sensation and irritability, since experiments seemed to 
show that no pain was experienced by removal of portions of 
the hemispheres, nor convulsive movements produced by direct 
stimulation of either the white or gray matter. It has there- 
fore been claimed that the hemispheres could be called into 
action only in response to a sensory impression transoiitted to 
its cells through sensory ner\'es, and that it was incapable of 
transmitting or appreciating artificial forms of stimulation. 
In 1870, however, Fiitsch* and Hitzig' discovered that certain 
parts of the gray matter of the hemisi)heres of the brain of a 
dog responded to a weak galvanic current, and these investi- 
gators were thus enabled to locate centers where certain well- 
defined movements could be produced at will. These experi- 
menters found (1) that the centers of motion were always 
confined to the anterior parts of the hemisphere ; (2), that 
the action on muscles was a crossed action^* i. e., on the side 
opposite to the stimulation ; and (3), that, after severe haemor- 
rhage, the excitability of the gray matter disappeared, thus 
possibly accounting for the negative results of previous ex- 
perimenters in the same line. 

The centers of motion discovered by these experiments 

* Reichardt u. du Bois-Ravmond's " Archiv," 1870. 

* Hitzip, •*Da8 (Jehirn,' 1874. 

' Brown-S6(iuard har4 shown that, in exceptional cases, this law may not be Bustained 
by clinical facts. " Lancet," 1876. The anatomical researchci* of Flech^ig, however, tend 
to explain the exceptions to the general rule (see pages of this Tolame referring to the 
*' pyramidal " fibers of the medulla oblongata). 



FUNCTIONS OF CEREBRAL CORTEX. 69 

seemed to be connected with parts which were widely sepa- 
rated, and arranged with little apparent system ; thus the 
muscles of the neck were found to respond to galvanism of a 
center in the middle of the frontal convolutions, while a cen- 
ter adjoining it caused a response in the extensor and abduc- 
tor muscles of the fore-leg, and others in movements of the 
eye and face. Ferrier* has of late repeated and confirmed 
many of the results obtained by the experiments of these 
German investigators." 

The effects of removal of the cerebral hemispheres of ani- 
mals have been studied largely upon birds and the monkey 
tribe, and with results which are comparatively uniform. 
Without entering into detail as to all the effects which follow 
such a procedure, in case the basal ganglia are left intact, the 
general result may be given as follows : The animal seems to 
be able to execute all the movements natural to it, even when 
complex coordination of movement is required ; but the intel- 
ligence seems to be impaired, and some unusual stimulus must 
be present to prompt any attempts at motion. As a result of 
this conclusion, the mechanism of coordination of movement 
is evidently not situated in the cerebral hemispheres. 

Flourens,* from a series of experiments made in 1822 and 
1823, concluded that the removal of the cerebrum entailed an 
entire loss of will power and also of the perceptive faculty, 
and that the memory was utterly destroyed. Bouillaud,* in 
1826, differed from Flourens as regards the perceptive fac- 
ulties, as sigM and hearing were shown to be unaffected ; 
and these results were still further made manifest by the re- 
searches of Longet,* who proved also that taste remained. 

A careful study of the phenomena which accompany cer- 
tain pathological lesions of the brain in the human subject, 

' ** West Riding Reports," 1878 ; " Functions of the Brain," 1876. 

* A lugp number of dutintt centcn of motum are mapped out by this author on A 
ditgrmmmatio chart. The reader is referred to Fig. 26 of tliis volume. 

* ** Redierches expdrimcntales sur les propridtes et Ics fonctions du syst^mc nerreuz,'* 
PteU,1842. 

^ *' Reeherdiee ezpdrimentales sur lea fonctions du cerreau." 

* **Aiiatomi6 et physiologie du systdmc nerveux," Pari.<, 1842. 



70 



THE MB A IN. 



■ 



such aa laceration or pressm-e from tlie eflfusion of blood, soft- 
ening of the cerebral substance, etc., if taken in eonnectiiiA 
with the later results obtained by experiments upon tiTiiqt 
animals, throws considerable light npon the functions of cer- 
tain distinct portions of the encephalon. 

Softening of the cerebral hemispheres and the d^eneift- 
tive changes which often follow an extravasation of blood 
into their substance are generally indicated by altprarions in 
the intellectual condition of the patient, thus conlinmn^ th« 
physiological exjieriments upon the hemispheres. Among 
the many forms in which this impairment of intellect may 
be manifested are recognized an impairment of various Ijpeft 
of memories ; a tardy, inaccurate, and feeble connection of 
ideas ; an iiTitability of temper, with a childish susceptibilitT 
to petty or imaginary annoyances ; easily excited emotional 
manifestations ; and a variety of phenomena denoting abnor* 
mally feeble intellectual power. 

Hugh lings- Jackson* has shown that there is clear evidence 
to prove that disease of the gmy matter of the convolutions 
of the hemispheres of the cerebrum may not only prodnoe 
delirium, as in meningitis, but sometimes cmtvulsions^ either 
of an epileptiform character or confined to particular groups 
of muscles. 

Landois* and Hitzig* both announce the fact that, when 
the motor areas upon the convex surface of the cerebrum^ 
which control the movements of the extremities, are excised, 
a rise in the femperalure of the corresponding limbs takes 
place and lasts for some months. A relationship has, more- 
over, been observed between the bmin cortex and the beat of 
the heart (Halogh*); an alteration in the arterial pressure 
(Bochefontalrit''); contmctlon of the bhuider, spleen, and 
uterus; an increase in the flow of the wiU\ni; and a dilating 
effect upon the pupil The exact locnlizAlion of some of these 
latter centers can not, an yel^ b^ ctm?«lde!Vfl m jKisitive. 



MOTOR SPEECH CENTER. 71 

Stimulation of the cerebral surface has been observed to 
result in a well-marked hcBTnorrhage of the lungs by Noth- 
nagel.* 

Most authors recognize to-day the existence of a " msual^ 
center; an ''avditory^ center; a ^Hactile^^ center; centers 
for smell and taste ; a motor speech center ; and centers for 
movements of the limbs and face. 

The 'motor center of articulate speech is one of the most 
definitely settled points in cerebral localization. 

There are two forms of aphasia, which are clinically recog- 
nized, viz., the amnesic or sensory j and the ata^nc or motor ^ 
varieties. In the former, the memory of words is utterly lost, 
so that the patient is not only unable to express his ideas in 
articulate sounds, but he is also unable to write them, thus 
showing that the words themselves have been forgotten. In 
the ataxic variety, however, the memory of spoken or written 
words still remains, but the ability to so coordinate the mus- 
cles of articulation as to pronounce the words is impaired, 
so that the person so afSicted can write his ideas intelligently, 
but can not utter them. 

Aphasia is not to be confounded, however, with other dis- 
eases where the ability to talk is apparently absent, such as 
occurs in the insane (who often refuse to converse from mere 
obstinacy), in those types of paralysis which affect the entire 
muscular mechanism associated with articulation, in hysteria, 
chorea^ and nervous affections, and in the aphonia of laryn- 
geal inflammation or paralysis. 

The credit of the great discovery that the motor center of 
articulate speech could be localized in the third convolution 
of the Irft anterior lobe of the cerebrum is generally awarded 
to Broca.* Some twenty-five years before he made the pro- 
fession alive to the investigation of the subject, however, the 
same motor impairment or loss of speech was shown to be a 
frequent accompaniment of hemiplegia of the right side of 
the body by Bouillaud and Marc Dax * ; and in 1863, or there- 

1 *«CbL med. WiM.,"" 1874. * Broca, ** Bui. de la Soc Anat./* Aug., 18dL 

* A paper read before the Medical CongresB at MontpeUior in 18S6. 



n 



TEE BR A IX. 



aboQt, the views of Broca and of IIngliling?i-Jack8ott' 
given to the profession, in which they both limit the le^io 
of motor aphasia to the parts supplied by the left midd 
cerebral artery. In 1863, the investigations also of tlie 
of Marc Dax ' located the lesion somewhere in the anterior i 
middle portion of the frontal lobe of the left side, and it 
results of still more recent investigations upon the siib| 
seem to point to the ''island of ReiP' as a frequent seatnf 
this peculiar type of paralysis. 

Viewing the fact that articulate speech is a thing leame^H 
by use^ it has been suggested that, in most j>ersons, one sit^l 
of the brain only has been educated for that purjyose ; that 
we ai'e, in fact, l^^tbralned in respect to speech in the sai 
way that we are right-handed in respect to many brKlilj 
movements.* In support of this theory the j^hysiologic 
fact is adduced that, in most people, the left hemisphc 
of the cerebrum is larger and more convoluted than t\ 
right. 

While it is demonstrated that the cerebral lesion in ajihs 
aia involves, in the great majority of cases, the left side, st 
there have been several cases recorded where the right sic 
has been shown to have been the seat of disease/ Such dig 
coveries tend to cast a doubt upon the left side being moi 
closely connected with the power of articulate sjjeech thai 
the right side. Some anatomists have endeavored to explaii 
the frequency of the lesion upon the left side of the brain a^ 
a result of the fact that emboli (which are the most frequen^ 
cause of the disturbance to those parts supplied by the middl^ 
cerebral artery) find a much more direct course upward npoc 
the left side than upon the right, in consequence of the angli 
at which the innominate artery leaves the arch of thenort^ 
which favoi's the passage of an embolus by rather than inii 
its month ; while the left carotid artery is situated at 

' Hi^tilitigs-Jftckaoii, **Clin)ot1 ami PhysialogtcAl B«*eirchc*i on I be Nvrvcnui 
if 

* M. 0. Dfti, as qtioted hf Dodde and A. Flint, Jr. 
ijmi. Fo4(cr, Qp. eit,: Fcrricr, "Functions of tlu' Umin/* 
; ^Ikf^i, BrQ&dbent, Biitenuji^ Mcissncr, 13«rtin, Scpiio, &nd otfaen. 



APHASIA, AS A SYMPTOM. 73 

highest part of the arch, and its mouth is so directed as to 
arrest rather than avoid any floating particles in the blood 
current. In case of such movable particles being arrested 
either by the innominate or left carotid arteries, the most 
direct course in both instances wiU be toward the middle cere- 
bral arteries, and thus aphasia will generally be produced 
with hemiplegia upon the side opposite to that where the 
embolus may be found. 

The following deductions relative to disorders of speech 
may aid in recognizing the seat of the lesion during the life 
of the sufferer : 

1. The cortex of the posterior part of the third frorUal 
convolvtiorij and possibly also the island of Heily presides 
over the coordination of the muscular acts necessary to 
speech. It also stores the memories of such acts, so that any 
combination of articulate sounds can be voluntarily repro- 
duced when the proper form of excitation is furnished (chief- 
ly in response to sight or sound impressions). 

This center is connected by *' associating fibers" with the 
centers of hearing (first temporal convolution) and those of 
sight (the occipital convolutions). It is also put in com- 
munication with the nvAilei of the facial^ hypoglossal^ 
the pneumogastric^ and glosso-pharyngeal nerves (within 
medulla) by means of two distinct tracts of fibers, viz., the 
" hypoglossal cerebral tract" and the so-called "speech tract," 
which pass through the internal capsule, the cms, and the 
pons, in order to reach the medulla. 

Thus, this cortical center of coordinated si)eech-movements 
is capable of receiving excitation from the centers of hearing, 
when replies to si)oken language are demanded ; and from 
the centers of sight, when written or printed language calls 
for a verbal response. It is also put in direct communica- 
tion with the ner\'es which preside over the apparatus of 
speech (whose nuclei of origin are situated within the me- 
dulla). 

2. The form of amnesic aphasia known as ^^ word deaf- 
ness^^ (Kussmaul) indicates the existence of a lesion of the 



THE BRAIN. 



first temporal convolarion' of the left side, which has iii< 
paired the memories of spoken laDguage. Hearing may nut 
be impaired, although the appi-eciation of words, niiisir. f'!<\, 
may be totally absent. 

3. The condition known as ^^ word-blindnesf^^^ ^Kussmatilf 
indicates tht? existence of a lesion of the left occipital lobe, 
which has impaired the memories of written or prin^-n ^^m- 
bols of language, numerals, familiar objects, etc. 

4. The conflition termed ^^^ paraphasias^ by Kiissmnal (i^ 
whieli the amnesic and ataxic varieties of aphasia seem to be 
peculiarly combined) may be excited by a lesion which inter- 
feres with the action of the associating tracts of fibers, be- 
tween the areas of hearing or sight and the motor speech eea- 
ter of Broca (Wernicke)* 

5. The condition of imperfect speech termed ^^anarthria^ 
is produced by a lesion of the medulla, which interferes with 
the functions of the nuclei of the cranial nerves assoc*iated 
with speech. It is occasionally obsei-vt^ in connection with 
focal lesions of the floor of the fourth ventricle. These cases 
are to be differentiated from aphasia of cortical oiigin by the 
coexistence of other symptoms produced by the medullary 
lesion. 

6. In order to properly pronounce any word, it i^ essential 
that both the cortical center of speech, and also the nuclei of 
the medulla, which are associated with itj must be called into 
action. 

%, The peculiar course which the fibers of the *'spe 
tract'' take within the cerebral hemisphere sheds light up 
these reported cases of aphasia where the lesion was sitiiat 
poHeriar to the cerder qf Broca. These fibers run from the 
third frtmtal gyrus close to the surface of the hemisphere, 
and in an antero-posterior direction (passing in tlie extern; 
capsule), to reach the posterior part of the lenticular nucle 
They dip at this point into the posterior part of the internal 




* In right buTided tubjects the left h«miiphcre, and in left-hiindi?^ siabjc^ta ih« Hght 
betntHphere, w^mn to moDopoliEe the function of ioaod^mterpretAtioa to thi^ 6p0«cb 
center* 



APHASIA, AS A SYMPTOM. 75 

capsule. They then pass through the middle part of the crus 
and pons to the medulla (Wernicke). Within the internal 
capsule, the fibers of the "speech tract" lie (according to this 
observer) between the optic fibers and those of the sensory 
tract. 

8. Should aphasia be developed as a result of a lesion of 
the internal capsule, hemianopsia or hemianesthesia wovM 
he liai>le to coexist^ on account of the relationship of the optic 
and sensory fibers of the capsule to the speech tract. 

9. It is possible to have aphasic symptoms develop as a 
result of a lesion within the crus or pons. This is because 
the speech tract passes through them to reach the medulla. 

10. The cortical centers of hearing, smell, and taste are 
probably associated (wholly or in part) with the correspond- 
ing organ of the opposite side. Hence, we may clinically 
refer an abolition of the function of hearing (when due to a 
cortical lesion) to the hemisphere opposed to the deaf ear. 
"Word-deafness" may ensue, however, when the centers of 
hearing of only one cerebral hemisphere are involved. In 
right-handed subjects, the left superior temporal convolution 
appears to govern this function ; while, in left-handed sub- 
jects, the right superior temporal convolution assumes it. 
This is probably due to the fact that the hemisphere which is 
the most exercised becomes more rapidly developed. 

11. When the third frontal convolution is alone diseased, 
the i)atient will be able to understand spoken or written ques- 
tions perfectly, but will not be able to coordinate the move- 
ments of the speech apparatus requisite to a reply. 

12. When the superior temporal convolution is alone dis- 
eased, the patient can not recognize or properly interpret 
spoken language. He may, however, be able to repeat single 
words when propounded, but not sentences. Exclamations 
of various kinds may be uttered by these subjects when irri- 
tated or distressed ; but they are more or less involuntary, 
and often irrelevant. 

13. When the associating fibers between the different 
centers functionally connected with si)eech are alone diseased. 



70 



TBE BBAIN. 



the patient can comprehend written or spoken language 
fectly ; but, in talking, such a subject is apt to int* 
frcjm time to time, some irrelevant and unexpertpd w 
sentence in place of the one desired. 

The Pre- frontal Lobes. — There are innumerable 
on record whem the frontal lobes anterior to the motor oen-' 
ters have suffered frightf nl lacerations and loss of Bub9tanc«% 
and yet recovery has t^iken place ; and where dise4ise of an 
extensive charxicter has also produced negative resulta, both 
as regards motion and sensation. This region is often called 
the "pre-frontal lobe." ^J 

A crowl>ar ha»s been shot through the head^ and recoveif^ 
followed.' Again, Bouillaud' reports the passage of a bullet 
through the frontal lobes with a like result, and with no effH 
upon sensation or motion. Cases somewhat similar are 
corded by Trousseau,' Congreve Selwyn,* Pitres,* Moi^ 
Marot,' Tavignot, and others, all of which go to prove t\ 
possibility of the most serious injury to this portion of 
cerebrum without symptoms indicative of its presence, 
the other hand, numerous cases of haemorrhage and of a 
within the frontal lobes, as reported by Andral/ Hertz, 
Begbie, and others (quoted by Charcot and Ferrier), show the 
same absence of posit he tliagn^ysUe symj^tojas either in sen* 
sory or motor paralysis. 

From such sources of clinical rea^soning, as well as from 
the physiological deductions which experiments upon ani- 
mals have taught, the following conclusion of Ferrier* is 
value to the reader: ** With such evidence before us, we 
not regard cases in which, with lesions of the priefron 
lobes, sensation or motion has been affected as other than 
cases of coexistence or of multiple lesions^ whether organli 
or functional/' 



* BijBjelow, **Atn. Jour, of Mod. Scicnoen/' July» 1850; narlow, " Recorery from 
PiioMW of an Iron Bftt througb the Ilcml "; *' Keporls of Mms. Med. S<*<*,,** n<wton, lS6fl 

* Op rH, • Quoted by Peter and Ferriw» 

* ** London Uncct,** FebruAry 28. 1838. • *' L6fk>iiA du Cuntn? Onh^' 1871 

* •* Prog. M«d.," Fcbnary 2ft nm] June ?{, 187«. ' " ninlqti© M6dicaJe,^' 
» *' LocftlisftOoa of Ombiml Disease/* New Vork, 1880v 



MOTOR AREA OF CEREBRUM. 77 

» 

The Motob Regions of the Cerebbum. — It may now be 
I)08itively stated that the bases of the three frontal convolu- 
tions^ the convolutions which bound the jissure of Rolando^ 
and the para-central lobtUe upon the internal surface of each 
hemisphere of the cerebrum, are distinctly motor in their 
function. The distribution of the middle cerebral artery to 
this region gives to that vessel an importance not before ap- 
preciated ; since it is now known that the four or five branch- 
es which are given oflf from the main artery each nourish a 
separate area of brain substance, and that emboli may ob- 
struct either the trunk or some of its individual branches. It 
is thus i)ossible to' explain how the basal ganglia may still 
X)erform their functions while other parts supplied by some of 
the cortical branches may be imi)aired. 

The preponderance of clinical testimony goes to show that 
most of the destructive lesions which are associated during 
life with paralysis of voluntary motion are confined to this 
motor area, although a rare case is on record' where the 
motor area was the seat of cystic disease, and still voluntary 
motion remained unaflfected. It is a matter of great doubt 
whether the gray matter of the convolutions was impaired, 
even in this case, in spite of the existing lesion. 

The eflfect of very extensive lesions aflfecting the motor 
area of the monkey (which is commonly used for experiments, 
as the nearest approach to the type of mankind) may be sum- 
marized as follows: 1. A hemiplegia, which is at first abso- 
lute ; 2. An improvement in associate, alternating, or bilateral 
movements, but no improvement in voluntary motion. 

Respecting this point, I quote from Fender's work as fol- 
lows: 

** As examples of the improvement which follows the on- 
set of the hemiplegia, the hand becomes more paralyzed than 
the arm, the arm more than the leg, and the lower facial 
movements more than the upi)er; while the muscles of the 
trunk are scarcely, if at all, affected.^' 

> Suit, •* ArcUT fttr PiycbUtrie," 1874. 

' Ferrier, '* Localization of Cerebral Disease.** 



78 



TEB BRAIK. 



In roan the hemiplegia is exhibited chiefly upon the jod* 
|Opposite to the existing lesion/ if the motor area, the corpus 

itum, or the motor part of the intemal cnpsiUe be the 
seat of disease. This paralysis is often aceompanied by mn 
tuUive museular matmienU or rigidity of the paralysed 
parts in its early stage, and, later on, by rigidity and meim 
sclerosis. 

The researches of Pitres* have shown that the same resolti 
as those dependent upon a lesion of the pray raal^>er of the 
convolutions within the motor area follow when the lesioc 
affects the white substance of the brain* which inten-eae* 
between the gray matter covering the motor area and flie 
basal ganglia beneath them, and he therefore urges a system 
of nomenclature of the different portions of the **centrii© 
ovale," based upon sections of the brain made in cemdn re* 
gions so as to show special parts. 

It is by means of these researches that we are enabled to 
explain those cases where rigidity or muscular spasms ac^om* 
pany an attack of hemiplegia, from an effiision into the Int- 
er al ventricles of the brain ; and where cerebral softtming or 
hmnorrhage^ which does not affect the gray matter of the 
convolutions or the basal ganglia, produces a permanent pji- 
mlysis of the side of the body opposite to the lesion. 

When sudden hemiplegia occurs as a result of haemor- 
rhage into or traumatism of some portion of the motor area, 
the condition of paralysis is liable to improve in those regions 
of the body whei'e the special motor center of that part re- 
mains unimpaired, but the paralysis will usually remain per- 
manent in that part of the body whose motor center is de- 
stroyed* This fact, when properly interpreted^ may often 
prove a most valuable guide in diagnosis. 

Special Centers of Motion.— At the base of the, ^r^^yron- 
tal conmlutio^n^ and extending slightly into the second /ran- 

* Tbe fftct thm all the motor fibers do not decuflfl^to lo Uie iiiedullA oblongaU (FI^cli. 
■ig) eiplaiiis the exocptiont to thiff mie. 

» ** Unions du Centre Oriilc,'* P*rii, 187T. 

' Thii portion eoatoini the 6l>cr« of tlie ini^moi eapmU r»difttiag to re*ch the i 
regSoof of tlM oonex. (Sot Fig. S. ) 



SPECIAL CENTERS OF MOTION. 79 

tal convolution^ in the brain of a monkey, a distinct center 
may be located which exerts a sx)ecial inflnence upon the 




Fm« 26.— <8iid!f viW of the brain of man and the areat of the eertbral oonvduiicne, 

(After Ferrier.) 

1 (on Uw postero-parietal [superior parietal] lobule), adTanoe of tbe opposite hind-limb 
Ai in waUdng ; S, 8, 4 (around the upper extremity of the fissure of Rdando), com- 
plei moToments of the opposite \^ and arm, and of the trunk, as in swimming ; 
a, 6, c^ <f (on tb« postero-parietal (^posterior central] oonTolution), indiridual and 
oombined moTements of the fingers and wrist of the opposite hand; prehensile 
mofements ; 6 (at the posterior extremity of the superior frontal convolution), exten- 
sion forward of the opposite arm and hand ; 6 (on the upper part of the antero>parie- 
tal or ascending frontal [anterior central] conTolution), supination and flexion of the 
opposite fore-arm ; 7 (on the median portion of the same couTolution), retraction and 
eferation of the opposite angle of the mouth by means of the zygomatic muscles ; 8 
(Wwer down on the same oonTolution), elevation of the ala nasi and upper lip with 
depreasion of the lower lip, on the opposite side ; 9, 10 (at the inferior extremity of 
the tame oonTolution, Broca*s convolution), opening of the mouth with 9, protrusion, 
■ml 10, retraction of the tongue— region of aphasia, bilateral action; 11 (between 
10 and the inferior extremity of the postero-parietal convolution), retraction of the 

risite angle of the mouth, the head turned slightly to one side ; 12 (on the posto- 
portions of the superior and middle frontal convolutionB), the eyes open widely, 
the pupils dilate, and the head and eyes turned toward the opposite Hide; 18, 13 (on 
the supni-mafginal lobule and angular gyrus), the eyes move toward the opposite side 
with an upward 18, or downward 18* deviation ; the pupils generally contracted (cen- 
ter of vision, according to the author) ; 14 (of the infra-marginal, or superior [first] 
lemporo^henoidal convolution), pricking of the opposite car, the head and eyes 
turn to the opposite side, and the pupils dilate largely (center of hearing). Ferrier, 
moreover, places the centers of taste and smell at the extremity of the temporo- 
sphsaoidai bbe, and that of touch in the gyrus undnatus and hippocampus major. 



80 



THE BBAIK 



head and eyes. Thus, to quote from Ferrier, whose research- 
es have been remarkable for the apparent accitraey of many 
of his dedactioBs, stimulation of this center causes ^^dem- 
Hon of the eyelids^ dilatation of the pupils^ co'fjjugate drri- 
aiion of the eyes^ and turning qf the head toward th^ oppo^ 
site sidey (See No. 12 in Fig. 26.) 

That this same center seema to exist in the human brain is 
to be inferred from the cases where a hUateral deviatian qf 
the eyes has been observed, which, in some cases, has abo 
been associated with a lateral deflection of the head. This 
subject has excited the interest of Hughlings- Jackson,* Priest- 
ley Smith,' Ferrier,* and Charcot/ and cases which seem to 
sustain the theory of an oculo-motor function in the frontal 
convolutions have been reported by Chouppe, Landouzy,' 
Carroll, Smith, Horsley, and others. An eflfort lias been 
made to explain these ocular symptoms by some associa- 
tion ^ith the angular gyrus, but apparently without maeh 
ground. 

The center of motion for tlie muscUs qf the limbs is not 
yet as positively ascertained as the oculo-motor center, al- 
though some interesting experiments have been made to 
decide whether the corresponding point of the brain of man 
is analogous, in its control over the leg, to that of the monkey 
tribe. As an example of the ingenuity shown in research. 
Bourdon* and Luys' have endeavored to demonstrate a^rcjpAy 
of certain parts of the brain after ampntation of the limbs, 
and thns indirectly to prove the normal use of the p^arta 
which had atrophied from disuse. The use to which the 
monkey puts his tail, since it serves the purpose of an addi- 
tional hand in some instances, renders the application of 
movements of that organ to those of man a matter of appar- 
ent difficulty, and the center of motion for the tail of the 

' ** Ophihftlmolof^ Id its Relatioot lo Ocnentl Medicine," ** Lancet," May, 1877, 

* '' BiUtend Dcfifttknu of die %ft%*' ** Birminghum Med. Review/' 1876. 
*Op,fiL ^Op, dt. 

* *" Bl^phmroptoM drfbimle/' *' Artib. G^ de MM./* Aug., 187*7. 

* " Recbercbei cHniqncB sur Ici ^ntrefl moteurii/* P«ri«, 1877. 
' •• runctiwB of the Brain,'' N.'« Vmkv 1882 



SPECIAL CENTBB8 OF MOTION. 



81 




Fto. 26. — Upper view of the brain of man and the tituaiion of areoi of the cerebral 
eonvohUUme. (After Ferrier.) 

1 (on the postero-parietal [superior parietal] lobule), advance of the opposite hind-limb 
ai in walking ; 2, 8, 4 (around the upper extremity of the fissure of Rolando), com- 
plez rooyements of the opposite leg and arm, and of the trunk, as in swimming ; a, 
ifCfd (on the postero-parietal [posterior central] oonTolution), individual and com- 
bined movements of the fingers and wrist of the opposite hand ; prehensile move- 
ments ; 6 (at the posterior extremity of the superior frontal convolution), extension 
forward of the opposite arm and hand ; 6 (on the upper part of the antero-parictal 
or ascending frontal [anterior central] convolution), supination and flexion of the 
opposite fore-arm ; 7 (on the median portion of the same convolution), retraction 
and elevation of the opposite angle of the mouth by means of the z3'gomatic 
imiseles; 8 (lower down on the same convolution), elevation of the ala nasi and 
upper lip with depression of the lower lip, on the opposite t<idc ; 9, 10 (at the in- 
ferior extremity of the same convolution, Broca's convolution), opening of the 
month with 9, protrusion, and 10, retraction of the tongue — region of aphasia, 
bilateral action; 11 (between 10 and the inferior extremity of the postero-parietal 
eoDTolution), retraction of the opposite angle of the mouth, the head turned slightly 
to one side ; 1 2 (on the posterior portions of the superior and middle frontal oon- 
volations), the eves open widely, the pupils dilate, and the head and eyes turn 
toward the opposite side ; 13, 13 (on the supra-marginal lobule and angular gyrus), the 
•▼M move toward the opposite side with an upward 18, or downward 18* deviation — 
tiie pupils generally contracted (center of vision); 14 (of the infra-marginal, or supe- 
rior [nrft] teroporo-sphenoidal convolution), pricking of the opposite car, the head 
and eyes turn to the opposite side, and the pupils dilate largely (center of hearing). 
Ferrier, moreover, places the centers of taste and smell at the extremity of the tem- 
poffMlrfiOBoidal lobe, and that of touch in the gyms undnatus and hippocampus m«Jor. 



82 



THE BRAIN. 



monkey can hardly be applied to the brain of man witl 
bringing comparative anatomy into prominence. 

Paralysis of the leg, when dependent solely upoo rerebnl 
lesions, is seldom separated from a similar condition of the 
ujiper extremity, although a few rare ca^es of tliat character 
are on record ; bnt the rule of Lucas ChampionniSre may l^ 
considered as approximately correct, m., that, to exi>ose the 
center of motion for the muscles of the leg, it is nec^ssarr 
to trephine over the tipper extremity of the fi^,^ure of 
Rolando,^ Horsley* locates the center for the big toe in the 
paracentral lobnle, and he includes the following parts in the 
motor area of the lower limb : the upper part of the two cen- 
tral convolutions, the superior parietal convolution, and the 
base of the superior frontal gj^nis. 

The centers of motion for the muscles of the different re- 
gions of the upper extremity occupy a much larger sim» 
upon the surface of the cerebrum than those of the lower ex- 
tremity, as might have been expected when we consider the 
amount of intelligence which the hand exhibits.' Ferrier 
has pointed out certain motor ai-eas for the various move- 
ments of extension, adduction and retraction, supination and 
flexion, and centers for the actions of the wrist and finger 
muscles,* 

The close proximity of those centers which control the 
facial and oral muscles to the centers governing the motions 
of the hand possibly explains why movements of retraction 
of the mouth occur when the hand ij< brought into powerful 
action ; and also the fact that paralysis of certain groups of 
muscles situated in the upper extremity are commonly asso* 
ciated with some form of facial paralysis. 

From a careful analysis of cases where paralysis of the 
upper extremity was confined to certain sets of muscles, tl 

' For the surgical f:Me to locate the situation of that fiseure upoa tbe exterior i 
(ace of tbc skull of a Lining aubjeet, the reader is referred to & suNequcQt page of ^ 
chajiter 

* ''Am. Jmr, Med. Scietioea," April, 1887. * Sir Cbarlei BelU ""The Huican Haad.'' 

* fn pagea 79» 81 of ihis volume, tbe centers of Ft-rrter are »bowii in a diai^^inmatl 
cut, and tbe apedal action of each ffiwea In the deaoriptive text which aooaaipamee it. 



SPECIAL CENTERS OF MOTION. 83 

resnlts seem to i)oint to the ascending parietal and the upper 
portion of the ascending frontal convolutions of the cere- 
bram, as the probable seat of disease; and lesions of the 
ctscending parietal convolution have been found, both by ex- 
X)erimental research and by pathological deduction, to affect 
the hand in particular. In further support of this statement, 
the results of the examination of the brains of persons who 
had suffered amputation of the hand,' or who had been char- 
acterized by a congenital absence of that member," show an 
atrophy of the part designated by the experiments of Ferrier 
as the motor center for its movements. 

According to the later observations of Horsley, the motor 
centers for the upper limb may be subdivided as follows : 

1. The uppermost part controls the shovZder. 

2. Below and posteriorly to the shoulder centers, the elbou) 
is represented. 

8. Still farther below and anteriorly, the wrist centers. 

4. Lowest of all, anteriorly, the^Tijjrer centers. 

6. Lowest of all, posteriorly, the thumb centers. 

The motor centers of the facial muscles occupy a region. 
in close proximity to those of the arm and hand ; and it is an 
exception to the general rule to observe paralysis confined 
exclusively to the face, since the muscles of some part of the 
upper extremity are generally affected simultaneously. 

Horsley subdivides the cortical area associated with facial 
movements as follows : 

1. The upper and anterior i)art governs the upper part qf 
the face and the angle of the mxmth. 

2. The anterior half of the lower part governs the move- 
ments of the vocal cords. 

8. The posterior half of the lower part governs the lower 
part qf the face and the floor qf the mouth. 

This observer includes the lower third of the ascending 
frontal and ascending parietal convolutions in the cortical 
area of the face. 

' Reported by Bourdon, " Centres moteun des membres,** Puis, 1877. 
• Gowen, article in '* Brain,** 1878, Part IIL 



TEE BRA IN. 

It may be also noticed, with some degree of ppactieal iU' 
terest, that motor aphasia is a nommon associate of either of 
these types of localized paralysis, since the center of Brocai 
liable to be aJso involved from its close relation to both i\ 
centers of the face, arm, and hand.' It is considered by some 
authorities that the absence of aphasia, in cases where \\ 
muscles of the face, arm, or hand are paralyzed, is probahh 
confined to lesions affecting only the right side of the cer 
brum. 

The lesions in which aphasia exists have been consider 
somewhat at length in previous pages of this chapter, Th 
fact that moat of the clinical cases recorded have failed the 
far to overthrow the discovery of Broca seems to place it uj 
a footing above that of mere empirical generalisation. Ca 
have been reported where aphasia has been the I'esult of frsicl 
ure of the left side of the skull in the region of the fi-unt 
lobes/ and also where recovery of the jxiwer of 8i>ee€b fo 
lowed the operation of trephining/ but it occurs most fr 
quently as the result of embolic obstraction of the inidc 
cerebral artery or of some of its branches/ 

Diagnosis of Cortical Motor Paralpsis.—The efferta of 
lesions which involve the corpus siriatum of either side, 
the motor bundles of the infernal capsule of the cerebrui 
dilTer but little from those of lesions which are confined 
the motor area of the cerebral convolutions, since the fil 
which are affected in either case are the same. 

After the effects of the shock of the attack have pasi 
away, the muscles which are panilyzed are usually thoa 
which are the most completely under the control of volition^ 
thus the lower muscles of the face are more affected t\ 
those upon the forehead or of the eyelids, since the lowc 
facial muscles are by far the most voluntary ; the muscle-s 
the hand are very markedly affected, even more than those 



* See the rektlcm of the facial eeotefii, Not 7, 8, 11, to thoie of the arm and ha 
KoA. 4, 6, <t, a, ft, e, d^ and to the oro-lingual centers, Noa. 9, 10, in Fig. th of thia roluiMi, 

» MacCairoac. '* Brain,** 1877, Part 11. 

'' Terrillon and Prouat, ** Acad, dc Mfidecinc/' Koverobcr, 187ft. 

* See re^Bcaruhe* of Meiasner, Charcot, Vulpian, Segiun, Bouin^ mA othor«. 



CORTICAL MOTOR PARALTSia. 85 

the arm ; and the muscles of the upper extremity more than 
those of the lower. 

No evidence of impairment of sensation can be discovered, 
provided that the posterior third of the internal capsule of 
the cerebrum has escaped injury. The nutrition of the para- 
lyzed muscles is apparently normal, and their electric con- 
tractility is not impaired. 

A tendency toward rigidity of the paralyzed muscles de- 
velops later on in the disease, which has been variously ex- 
plained by some authors (Charcot, Bastian, and Bouchard) as 
the result of a progressive sclerosis^ which descends along 
the motor tract of the pons Varolii, crus cerebri, medulla, and 
the spinal cord ; while the researches of Hughlings- Jackson * 
warrant him in discarding this explanation and attributing 
it to an unimpeded cerebellar iiifiuence^ which is no longer 
controlled by the cerebrum. Both of these hypotheses are, 
however, discarded by Buret," who considers the rigidity to 
be the result of simple reflex irritation. It will in no way 
add to the practicability of the matter contained here to enter 
into the discussion of the relative demerits of these theories, 
since those interested in the subject will find Ferrier's work 
on the *' Localization of Cerebral Disease" and many of the 
advanced works upon the pathology of diseases of the nervous 
system to contain all the desired information. 

One of the most valuable signs of paralysis dependent 
ui)on a lesion of the cortex is the fact that the condition is 
not one of complete hemiplegia, but rather of monoplegia^ in 
which 8i)ecial groups of muscles only are deprived of volun- 
tary motion. Thus, for example, the arm and leg may be 
affected together ; again, the arm, hand, and face ; the arm 
alone ; the leg alone ; certain movements only of either ex- 
tremity ; and all other possible combinations. 

Paralysis due to lesions of the cortex may often be transi- 
tory, if the lesion be slight and superficial ; or it may be per- 
manent, if deep and impinging upon the medulla. It is, fur- 

> " Medical Examiner/' April 6, 1877. « " Brain," Part I, 1877. 



TffS BBMK. 

thennore, frequently associated with rigidity in its eat^ 
stages^ which is a rare oecurreiic^ in central cerebral disease. 

In attacks of paralysis due to suddenly developed lesici 
of the cortex, consciousness is less frequently lost than 
similar lesions of the centml ganglia. Pain of a local cl 
acter within the head is often complained of by the 
spontaneously with the attack, or, when not so, it may 
sometimes elicited by percussion over the seat of the excitii 
lesion. 

The loss of consciousness which generally accompanies ii 
sudden lesion of the central ganglia is explained by Duret * m' 
due to a rapid displacement of the cerebro'Spiiial fluids wMch^ 
in turn creates a general disturbance of the circulation of 
cerebrum, since this tluid serves to establish a uniformily 
pressure throughout the brain. 

Ferrier' thus briefly summarizes the results of clinicaJ ob- 
servation bearing upon the diagnosis of paralysis de^iendfiiic 
upon destructive lesions of the cortex : " ^VTiile we can not 
be quite certain of the position or extent of a cortical lesion 
causing a sudden and complete! hemiplegia^ we may take 
monoplegia of the leg, or of the arm and leg, as an indication 
of a lesion of the upper extremity of the ascending conToln- 
tions close to the longitudinal fissure; brachial mono/ ^ ' , 
as a sign of a lesion in the upper part of the ascending n ^ lu Jl 
convolution, or, if the paralysis affect the hand more particu- 
larly, of the ascending parietal convolution ; bTachio-/acial 
monoplegia, as indicating a lesion of the mid*fron to-parietal 
region ; while facial and lingual monoplegia, or this con 
bined with aphasia, indicates a lesion of the lower part of tl 
ascending frontal convolution where the third frontal joins 
with it."' 

Irriiative Lesions of the Motor Area*— It is a wellrecc 
nized fact in clinical experience that certain symptoms, whicl 
are chiefly of a convulsive type, are dependent upon condi- 

« ** TmumntisiDM cMbrauV Th^ec, 1878; " ArehiT. de Physiologie," 1875, 

• Op. *^ 

* The cut (fig* SA) flhowis^ tho motor oeoten will tend lo explain tbeao dcdue 



^m^- 



SPASM OF CORTICAL ORIGIN. 87 

tions which create simply irritation of certain portions of the 
cerebrum, without any actual destruction of the gray or white 
matter. Among the various conditions which are especially 
liable to produce such local irritation may be mentioned 
syphilitic meningo encephalitis, simple inflammation of the 
same character, deposit of tubercle, superficial cysts or tu- 
mors of a more solid character, spiculse of bone, cicatrices 
from wounds of previous date, suppuration from caries and 
necrosis, etc. 

In the year 1867,* and still later, in the year 1871,* the 
general statement by which the clinical diagnosis of the situa- 
tion of irritative lesions of the cerebrum might be assisted was 
advanced by Callender, "that convulsive attacks were most 
commonly associated with sui)erficial lesions of the cortex 
situated in the immediate vicinity of the middle meningeal 
artery." Perrier, however, concludes, as the result of his ex- 
tensive facilities for observation, that, while this may be use- 
ful as a general rule, still affections of any portion of the 
cortex of the hemisphere may result in convulsions of the 
opposite side of the body, and he adds the statement that the 
seat of an irritative lesion can be less accurately determined 
than one of a destructive character, owing to the difllculty of 
determining the extent of the zone in which vital irritation 
concentrates itself. 

Hughlings-Jackson • has contributed much to the pathol- 
ogy of those conditions of the cortex, produced by irritation, 
which manifest themselves in the form of convtUsions. So 
great a prominence did syphilis have as one of the exciting 
causes of such irritation that the term " Jacksonian epilepsy " 
is now often used as synonymous with the convulsions met 
with in that disease. The theory which this author advances 
to explain these convulsive attacks is as follows : That irrita- 
tion of the cortex tends toward an abnormal accumulation of 
nervous energy, so that the affected part is under a state of 

> *' St. Bartholomew's HofipiUl Reports.*' 

• " Medioo-Chir. Trane/' 

» Op. di. Also, see " Medical Times and Gazette," 1875. 



THE BBAIK 



high tension, and, under certain conditions, this irrftal 
portion discharges itaelf in a sudden nnd explosive mai 
thus producing a subsequent exhaustion of ita poweii 
hence a convulsion, and often some type of monopltfgia 



J owing It. 



The convulsions dependent upon irritation of the cor 
may assume all of the diflFerent varieties produced by 
structive lesions of the motor area, and may even resnlr ia 
paralysis ; thus the leg may alone be affected with spa8ni, the 
aiTO alone, the arm and hand together, and the face alone, or 
in connection with the upper extremity. 

It may often assist in the localization of a lesion, which I 
creating the irritatiou of the cortex, to note carefully ti 
muscles affected at the onset of the convulsion. Such 
formation may enable the obseiTer (through a knowledge 
the motor centers) to trace the seat of the region within ll 
cortex which first exhibited a tendency to explosive diael 
of its nervous energy. Homley has utilized the guides so 
forded in trephining BuccessfuUy for cortical cerebiul lesion 

Thi: Sensory Reoions of the Cerebri m.— A part of tl 
parietal, the tern poro- sphenoidal and occipital lobes ai*e na^ 
accepted by most author as the portions of fhe cerebral eorte 
which can appreciate the perception of sensory hnprefi^iimn\ 

The experiraouts of Munk, made with a view of detemiii 
ing the area of common sensation in the cerebral coitex, Ic 
to the conclusion that the entire parietal cortex must be di 
stroyed, and the ascending frontal convolution as well, befoi 
complete and pex-manent ana3sthesia is produced on the opj 
site side of the body below the head. These results make tl 
motor area overlap the sensory area to some extent, and ten^ 
to refute the deductions of Ferrier, who places the center of 
tactile sensations in the tempoi*al lobe, and to ctmfirm the 
views held by Luciani and Exner. If a partial destruction o^ 
the sensory area of Munk be produced in animals, the 
{Bsthesia persists only for a few weeks, because the adjaceij 
r^ons learn to perform vicariously the functions of the pc 
destroyed. 



8EN80R7 AREAS OF CEREBRUM, 89 

Tripier, of Montpellier, France, has lately affirmed the 
conclusions of Mnnk, respecting the existence of sensory 
centers in the central convolutions, as has, also, Moeli, of 
Berlin. These three observers support the view that the motor 
and sensory centers of any one limb coincide. This view 
was advanced theoretically by Luys some years ago. 

Exner has collected from European journals all cases of 
cortical disease that have been associated with disturbances 
of sensation, and M. Allen Starr has lately performed the 
same labor in American literature. An analysis of the cases 
so collected seems to justify the conclusions of Munk and his 
followers, and to add some clinical suggestions of value. 
These cases demonstrate (1) that the cerebral cortex of each 
hemisphere appreciates sensory impressions from both sides 
of the body, but are chiefly associated with the sensory tracts 
of the opposite lateral half of the body ; (2) that the sensory 
area includes the central convolutions (a term used to cover 
the ascending frontal and ascending parietal gyri — see Fig. 
22) and the posterior part of the parietal lobe ; (8) that the 
sensory centers coincide to some extent with the motor cen- 
ters of similar parts ; (4) that no disturbances of general sen- 
sation have been known to result from lesions confined to the 
frontal, temporo-sphenoidal, or occipital lobes. 

It has been determined, with some approach to positive- 
ness of statement, that the posterior fibers of the crus are 
the principal means of transmission of sensory impressions 
from the i)eriphery of the body to the cerebrum, and the 
researches of Meynert have done much to demonstrate that 
these fibers are connected with the portions of the cortex 
which have been designated as the regions chiefiy associated 
with sensory i)erception. 

Duret,* Veyssidre,* and Raymond have shown by experi- 
ments that, when that part of the internal capsule which is 
ritoated between the lenticular nucleus and the optic thala- 
mus is divided, a loss of sensation is experienced in the opjK)- 

^qp.eiL • ** Sar llidinianesth^flie de caoM c^r^brale,*' 1874. 



THE BRAIN. 

site side of the body, but that, in some instances, some degrw 
of motor paralysis is also produced. On the other hand, 
these same observers have found that section of the anterior 
two-thii'ds of the internal capsule ' produces a distinct niotoff_ 
pamlysis, with no effect upon the function of sensory i>ereej 
tion of the parts paraljzed, save in a few instances, wbeit^ 
such a result of a fleeting character was detected. 

These deductions are fully sustained by clinical facta 
The collected cases reported by Charcot,* Pitrea,* Torek/ and 
many otliers, present a large mass of evidence to warrant tl 
conclusion that lesions of the posterior part of the intemi 
capsule are indicated by hemi-aniesthesia on the side of tt 
body opposite to the lesion. In such cases, tactile S€ 
is destroyed to the median line not only in the trunk, but alBO 
upon the face ; pain and the sensation of heat are likewis 
abolished ; but the contractility of muscles under the elecl 
current is not impaired or lost If we examine the mueoc 
membranes of the eye, nose, or mouth, the same condition 
destroyed sensibility will be detected, but the viscera remai 
sensitive. Furthennore, taste, smell, and hearing are some 
times rendered deficient, and, in some cases, are entii-ely al 
ished, on the side opposite to the lesion ; and the special > 
of sight is atfected in a variety of ways, which will be 
scribed in detail. 

In lesions of the internal capsule, blindness of the lateral 
half of both retinjD {hemianopsia)^ a« one would expect to 
find, does not exist ; but, on the contrary, a condition 
amblyopia occasionally results, w^hich is characterized by 
marked contraction of the field of vision, and especially so 
regards the perception of color. By consulting the diagrai 
given you in the description of optic nerve,* you will perceiv^ 
that the field for blue tints is the largest, and that red is nei 



^ S4ibsef|uciit pft^es which treat of tbe inlemal c«p«ul6 iriU explftiii the aituatloa of 
tbe ditTcrt^nt bundles which com|K)9e it, 

' ** Lemons fur tes tntladic^ dii sj^lkme iwTTeiu." 

• " Liftioni tlu Cctjtre Ovule," 

^ Sie Gnnet, '' LocAlizaciond tUu« Ics mdadlea c4r^bra1c8/' 1876. 

' 8e« page of this rolume ocmuiifiing a diagrmm bj Hlmchbcrg. 




8ENS0RY AREAS OF CEREBRUM. 91 

in point of size, while green comes last.' Now, in lesions of 
the internal capsule, the i)erception of these colors is apt to 
be impaired in the relative proportion of the size of the field, 
and thus green may be entirely lost^ while the vision of red 
or blue may still remain. 

It has been shown by Landolt,* who has done much to 
develop this special field of investigation, that the impair- 
ment of vision from intra-cerebral causes is not altogether 
confined to one side, but that the eye upon the same side as 
the lesion is somewhat affected, and rendered partially an- 
sesthetic. 

If we examine the eyes so affected, we can not discover 
by the ophthalmoscoi)e any organic disease or evidences of 
degeneration of either the optic nerve or the retina, provided 
that the examination is made early, before any late results of 
the blind condition of the eye manifest themselves as the 
effect of disuse.' 

As has been before stated, the condition of amblyopia and 
the absence of hemianopsia are in opposition to what the ef- 
fects of pressure upon the optic tracts would seem to suggest, 
but we stiU have a clinical fact to explain, viz., that hemi- 
anopsia does sometimes occur with attacks of hemiplegia. 
In such cases as these, we may conclude that the lesion must 
be so situated as to exert its influence upon the motor bun- 
dles of the brain and the fibers of the optic tract simultane- 
ously. The occipital cortex,* which is now regarded by most 
authorities as the probable center of vision, does not seem to 
exert any influence upon the motor apparatus, as is shown 
by its destruction in animals. 

The Occipital Lobes of the cerebrum have been stated to 
be properly included among the sensory regions of the cortex. 

' Violet hms a still smaller field, but it is not 8hown upon the chart. 

• " U Prance M«dicale," Feb. 8, 1877. 

* Any intra-cranial lesion which acts in such a way as to inereaae the intracranial 
prmntre may produce (in addition to other symptoms) the condition known as ** choked 
diak,*' or a neuro-retinitis. 

^ The reader ia referred to the lecture on the optic nerve for further information upon 
this point 



93 



TEE BEAm. 



Experiments of section, or even of complete removal of tbeJ*» 
lobes of one or both sides, however, fail to show any effect on 
general sensation or motility. Disturbances of sight' harp 
been positively pmduced by injuries to and morbid lesions of 
the occipital ronvolutions. The distribution of the fibers of 
the optic tracts to the cortex of the occipital lobes (prolwiWy 
to the cuneus) may be now considered as positively proved. 

It is claimed by HughJings- Jackson that irritatire lesions 
of the occipital lobes give rise to colmed perception of objects 
and other ocular sjiectra, and he further states that such evi- 
dences of defective perception are more common when the 
lesion affects the right side. 

The Temporo-sphenoidal Lobes are in relation with the 
bones indicated by their name, and lie partly on the base 
of the skull. The following deductions have been drawnu 
fmm experimental research, as to the special functions of 
this lobe and some of the adjacent convolutions, which 
require separate consideration : 

The apparent connection of this region with the speriidj 
sense of msion has been noticed by Hitzig, Goltz, and McKen- 
drick, the two former of whom confine their experiments 
the dog species, while the latter operated exclusively \i\ 
pigeons. Femer,' however, from a belief that other functioBdl 
could be demonstrated as pertaining to this locality, and from 
disbelief in the method pursued by Goltz,' as adapted to the 
requirements of experimental research concerning the fonc* 
tions of limited areas of the cortex, made a series of experi-| 
ments upon the brains of monkeys, and claims to have estal 
lished some new points of physiological interest, and, possibly,] 
of practical value in cerebral localization. 

The conclusions which w^ere drawn as the results of the] 
labors of this learned and original investigator may be thusi 
summarized: 



1 Munk eeems to have fMMiliTclj prored an MMciation of the occipital lobe irith, 
Tiston* 

• Op, eii, .- Fcrrier and Yeo, " Brain,'' 1880 ; Exner, " Brain,** Octcbor, 1880. 

* That of trephining over the fpot fkclectcd for ia?efftigAUoii, and washing awaj ^tm] 
brain bj a forcible stream of water. 



CORTEX OF TEMPORAL LOBES, 98 

1. In the angular gyrus"^ this observer thinks that in 
animals there is situated a center, which causes, on electric 
irritation, certain maoements of the eyes^ pupils^ and head^ 
but whose destruction creates no evidence of motor paralysis 
in the muscles of either the eye, its lids, or the pupil. Uni- 
lateral destruction, however, of this center causes blindness 
of the opposite eye, which proves but temporary ; while the 
destruction of both sides causes a permanent loss of sight 
in both eyes,* It would thus appear (to his mind) that the 
center of either side is, to some extent, connected with both 
eyes. 

2. In the superior temporo-sphenoidal convolution^ is 
found to exist a center which, under galvanic stimulation, 
creates a twitching of the opposite ear and an apparent modi- 
fieation in hearing of the opposite side, which it was found 
difficult to fully locate on account of the animal not being 
able to exhibit appreciation of modification of that special 
sense. As with the preceding center, destruction of this con- 
volution, upon one side, caused some abnormality of hear- 
ing ; but, when both sides were destroyed^ the animal became 
totally deafy although no motor paralysis could be discovered 
in either case. 

3. In the ?02/jer extremity of the lobe previously desig- 
nated, a center was found which seemed to exert an influence 
ni)on the special sense of smelly and also to create motions of 
the nostril and head which indicated excitation of that sense. 
In the regions adjacent to this convolution the special sense 
of taste became affected when destroyed ; and, when the con- 
volution and the adjacent region were destroyed, upon both 
sides, taste and smell were utterly lost. In regard to these 
two centers, also, unilateral destruction created the most 
marked effects upon the side opposite to the lesion, while a 
bilateral destruction abolished the sense altogether. 

' Regfons marked 13 in Fig. 25 of this Tolume. 

* The experiiDonUi of Munk, Luciani, Tamburini, Ferricr, Yeo, Dalton, and others, 
apon these centers leave the field, as jct, a matter for further invcHti^ation. The pre- 
ponderanoe of testimony goes to show that the statement of Ferricr is not tiuc of man. 

* See diagramnuitic eut on page 79 of this Tolume ; regions marked 14. 

9 



94 



THE BRAiy. 



4. In the region of tJie hippocampus some evidence was 

given of a center possessing the appreciation of tactile sensa- 

fioUj but the situation of the part rendered experiment upon 

it difficult, and somewhat less positive than that ux>on the 

areas previously discussed. 

c 




Fio. 27. — A diafjram illuftnifinp the courae of nerve impuUes in the 

(After Dixlds.) 

A, tho fM<>/»>r nyions of xho cowWA cortex, represented by arrow-hcads; B, the j 

rojio'Ut of tlie tvnh.al O'^rtix, i\|>ro-onto i by circles; C, commiBStiral fibers, oon- 
noctiivj the two re'^i»»n- of the c »rtc\ (i»i\>bable, but not positiTelj demonstrmted); 
I>, S(nxt>)'<; ncnr r?'- r.<^ tlie arnnv >h».\i.»ir the rmfriitettil direction of the impulse; 
K, tu^f"}' vtrvf fi'; :<. the arrow >ho\\inj: xho rrnfrifupal direction of the impulse ; 
1' S, '* o>j;)Mjc s/n ''ui'i " (the jMobal^lc motor panjrlijm at the base of the cerebrum); 
O T, "op'lr tlnilttinus'" [xho ]»nil>.ihle st n $•■»)' u j.'an;:lion at the base of the cerebrum); 
1. a few *f;w>rv r'hc-<^ possibly iM^nnrctcii with the "corpus striatum**; 2, a few 
vu^or fi'^rf, possibly is^imoctrii witli the "optic ibalanius." 

It is to be ivixivttod that the conclusions of this brilliant 
i'.ivostiirator as t(^ the situation of these special centers in the 
sensory rei]:it>ns of the cen^hrnm are not as positively sustained 
l\v clinical and patholoirical facts as were his conclusions 
ili'awn fn>ni ex]>eriinental research upon the motor area of the 
brain of the monkey tribe. Ferrier endeavors to explain the 
discrepancy l>et\veen the facts obtained by experiment and 
those afTonled by disease of the same regions in the human 
brain, by the hypothesis that the special senses may be gov- 



CORTICAL LESIONS OF CEREBRUM. 95 

emed by a bilateral rather than a nnilateral impulse, as the 
experimental facts jyertaining to the special senses of sight 
and hearing seem to warrant. This has not, as yet, been dis- 
proved, since all of the cases recorded have been of a unilat- 
eral character. 

To what extent these physiological subdivisions of the 
sensory area of the cerebrum may be regarded as of practical 
utility in diagnosis can hardly yet be determined, as the field 
is still a new one, and the collection of clinical and patholog- 
ical records is hardly suflBicient for a basis of positive deduc- 
tion respefeting many points yet in dispute. 

The contents of the preceding pages will probably enable 
the reader to appreciate the grounds which justify the follow- 
ing conclusions respecting the diagnosis of focal lesions of the 
cerebral cortex. 

A SUMMARY OF THE EFFECTS OF CORTICAL LESIONS OF TUB 

CEREBRUM. 

Lesions of the motor convolutions, when of small size, pro- 
duce some form of monoplegia^ and possibly a coexisting 
mono-ansesthesia with a loss of muscular sense in the part ; 
when of large size, a hemiplegia may be produced. 

Consciousness is not necessarily lost at the time of the 
attack. 

Early rigidity of the paralyzed muscles is often present. 

Cortical hemianesthesia will be produced when the entire 
I)arietal cortex is involved by a cortical lesion, and, in addi- 
tion, the balance also of the motor area, which lies outside of 
the parietal lobe. Such an extensive cortical lesion is rare- 
ly, if ever, encountered. We, therefore, do not observe co- 
existing hemiplegia and complete hemianaesthesia in cortical 
disease. 

Localized pain in the head is a symptom which is often 
present in connection \iith cortical lesions. If it be absent, 
percussion over the lesion will generally tend to excite. This 
step will also tend to increase the pain, in many cases, when 
it exists prior to this test. 



DO 



THE BRAIN. 



Coiividsians, when followed by transienl fifiarA's qf pa- 
ralt/sis {J acksonmn epilepsy), indicate an irritative It^ion 
the cortex. They are frequently encountered in cM^nnecti 
with syphilitic disease of the l>raiu. Subjectiye sensalio 
(par^sthesife) may also be excited in limited portions of 
limbs. 

Blindness of that half of each retina which corresponds 
to the cerebral hemisphere affected, occurs when extensive 
cortical disease of the occipital lol>e (chiefly of the etineu%») 
present. ^'-WorclMindness-- may also be produced by ledoi 
of these lobes (esi)ecially if upon the left side). 

Lesions of the first temporal convolution (chiefly npoo t 
left side) may produce abolition qf hearing^ and also the coi 
dition known as '^ word-deaf ness^'^ (see page 97). 

Lesions of the tip of the tempoitil lol>e may be the cau 
of abolition of the sense of smell, or of taste. The memo; 
of taste-and-smell' perceptions may also be impaired or lost. 

Ataxic aphasia and paraphasia may be developed as 
result of cortical lesions, which involve respectively 
speech center of Broca and the ''island of Reil/' 

The/a<?e is never rendered totally hemiplegic by cortical 
lesions. The conditions known as ^^ mono-ancesthesia^^ b: 
which we mean an impairment or total arrest of sensation 
some distinctly localized part, as, for example, the hand* arm, 
leg, etc., and also the condition known as ^^ monoparijeslhesia 
which signifies the existence of subjective sensations of a deft 
nitely localized character, are particuhirly diagnostic of cortf' 
cal lesions lying posterior to the fissure of Rolando. Th< 
former indicates a destructi^-e lesion, the latter an irritntin, 
lesion. 

The muscular sense is liable to be impaired (when a cartl 
cal lesion of the motor area exists) in the parts functionally 
associated with the limits of the part diseased. 

Monoplegia and monospasm seem to be peculiarly cling* 
nostic of a cortical disease anterior to the fissure of Rolando^ 
although Horsley's late observations show that this is not 
alwavs the case. 



J 



CORTICAL LESIONS OF CEREBRUM. 97 

The memories of sensory impressions are more frequently 
impaired by cortical lesions of the left hemisphere than of the 
right (as shown, for example, in ataxic aphasia, word-blind- 
nesfs, word-deafness, paraphasia, etc.). 

Motor memories may be impaired by cortical disease af- 
fecting the motor area. Subjects may thus lose a dexterity 
with the fingers, arm, hand, leg, etc., which they had acquired 
previous to the development of the lesion. A knowledge of 
this fact may sometimes aid in the localization of a lesion. 

Irritative lesions of the cortex of the cuneus (a part of the 
occipital lobe) may cause hMlucinations of vision. If one 
hemisphere only is affected, the objects seen will appear to 
lie on the side opposed to the lesion, and to move with the 
eyes as they are turned from side to side. 

Lesions of the ""Hsland of Reil^^^ or ^Hnsvla^ of the left 
side (Pig. 23), seem to create (in some instances) symptoms of 
ataxic apha^ia^ and also paraphasia (the substitution of 
wrong words). The motility of the face and arm qf th£ op- 
posed side may occasionally be impaired from cortical lesions 
of this region. 

Lesions of the cortex confined to the apex of the temporal 
lobe (Fig. 26) are liable to cause an impairment of the sense 
qf smeU or of taste (if destructive in character) or subjective 
odors and tastes (if irritative in character). 

Destructive lesions of the cortex of the motor convolu- 
tions (Fig. 26) is followed by a descending degeneration of 
the fibers which arise from these gyri. This may account (?) 
for the late rigidity of the muscles paralyzed, which is occa- 
sionally observed after such lesions. 

Cortical lesions of the base of the brain are especially liable 
to produce vomiting, choked disk, bilateral i>aralysis, and 
symptoms of impairment of some of the cranial nerve trunks. 
The cms, i)ons, and "island of Reil" may also be involved 
and give additional symptoms. 

Cortical disease of those frontal gyri which lie anteriorly 
to the motor centers (Fig. 26) is often attended with no symp- 
toms of a diagnostic character. The higher mental faculties 



98 THE BRAIN. 

may occasionally give signs of more or less impainnent. Con- 
nected thought, the control of the emotions, and concentra- 
tion of the attention are particularly difficult under such cir- 
cumstances. 

The memories of sound or sight impressions, as well as 
those of smell, taste, muscular movements, etc., may be sepa- 
rately annihilated by cortical disease. Cases of this charac- 
ter have been discussed under the head of Aphasia (see pages 
73 to 76 inclusive). 

SUMMARY OF THE PnYSIOLOGY OF THE CEREBRAL CORTEX. 

From the statements made in previous pages, we may 
summarize the functions of the cortex (the gray matter of 
the cerebral convolutions), as well as the symptoms which 
can be attributed to disease confined to that r^on, as fol- 
lows: 

1. Contiury to old statements, the cortex is capable of 
artificial stimulation. The functions of certain cortical areas 
have thus been determined with an approach to accuracy.* 

2. A well-defined relationship exists in man as well as in 
animals between the limited areas of the cortex and certain 
muscular groups. This has been confirmed by jwithological 
and clinical observation, and also by experiments made upon 
the human subject by Dr. Amidon, of this city.* The accu- 

* There arc at the prof^ont time three distinct schools among the experimental phjn- 
ologists respecting tlie subject of cerebral localization. Ferrier and Munk represent a 
faction which strenuously hold the view that the cortical i^i-ay substance can be mapped 
out into areas whose lindts are clearly (K-tined. as wvll as their indiridnal funcciooa. 
Goltz stands at the head of a selux^l which denies the awuracy of these riewa, and rap* 
ports the conclusion, orijriiially advanoeti by FIouhmis, that the brain can only act aa a 
whole. Exncr and Luciani (in Cs>mnion with their followers) occupy a ground which op- 
poses very sharply-detineil boundarit's to cortical areas, functionally associated with the 
various senses. They believe that ther^e areas overlap each other to a greater or leM 
extent. At present, the latter view seems to bo most perfectly in accord with clinical and 
pathological data. 

* Prize Es.«ay of 18v*^«>, ** Archives of Me<licine," April, 1S8«\ 

" Dr. Aniidon's experiments in c nbrnl htcallzntioH are based on the following propo- 
sitions: 1. Marked liKal variations in the teuiprraiure of the cephalic contents can be 
demonstrattMi by surface tfurnvvncterx. 2. Cerebral cx)rtical localization is now so far 
advanced as to warrant the assertion that the psychomotor centers for one half the body 
occupy a certain area iu the ccrebnil cortex of the opposite hemisphere. 8. Functioiial 



EXCITABLE REGIONS OF CORTEX. 09 

racy of Dr. Amidon's observations has been called into ques- 
tion by other experimenters since their publication ; but I am 
inclined to doubt the justness of the criticism. The counter- 
experiments seem to me to be defective in the methods em- 
ployed. Dr. Amidon has lately published some additional 
proofs of the ability of the cranial bones to transmit heat.* 

Dr. M. ADen Starr has collected, of late, all the cases re- 
ported in American literature which support the modem 
views of cerebral localization.' These supplement similar 
cases collected by Perrier, Charcot, Wernicke, Nothnagel, 
and others from the European journals. 

3. The excitable region of the cortex, where motor effects 
are chiefly produced, may be stated to be localized in the 
following parts : The ascending frontal convolution ; the base 
of the first frontal convolution ; the second frontal convolu- 
tion ; the third frontal convolution ; the ascending parietal 
convolution ; the superior parietal convolution ; the supra- 
marginal gyrus; and the para-central lobule. Now, let us 
see what centers pertain to each of these convolutions, accord- 
ing to the researches of Perrier : 

The center for movements of the lips and tongue (the motor 
speech center) lies at the base of the third frontal con- 
volution, near the fissure of Sylvius. (See 9, 10, in 
Fig. 26.) 

ACtiTitj of an organ implies increased blood supply and tissue change, and consequent 
deitaUon of the temperature of that organ. 4. Willed contraction of muscles presupposes 
an increased acUyity of the volitional motor center of those muscles in the cerebral cor- 
tex. Fr(MD this it was natural to make the deduction that voluntary activity in a periph- 
eral part would cause a rite of temperature in the pst/eho-motor center for that part, which 
might be hidicated by external cerebral thermometers. 

•* 8eguin*s self-registering surface thermometers were used, numbers of which were 
applied to the surface to be tested by passing them through holes in rubber straps se- 
cured to the head by buckles. The desirable points in the subject experimented on arc, 
a well-shaped head, thin hair, well-developed and trained muscles, power of facial exprcs- 
sUm, especially of unilateral facial movements and the ability to contract individual mus- 
cles, and moderate intelligence. A man U preferable to a woman, and a European to an 
African. The mode of performing and recording/ experiments and the liabilities to error 
are all fully described." (Report in " New York Med. Jour.," October, 1880.) 

* "Fkcts and Figures in Cerebral Thermometry." 

• ♦•Cortical Lesions of the Brain," *SVin. Jour. Med. Sci.," July, 1884. 



100 



THE BE A IN. 



Upon the flrst l^m~!feeond frontal convolutions" He fouiKl i 
center (see 12 in Pig. 20) : (1) Ft>r lateral motemenU 
of the head ^ (2) for eledolion of the eyelids / and (3) for 
dilatation of the pupil. 

The ascend Ing frontal convolution presents, from b«^low up- 
ward, the following centers: For elevation and depre4 
sio^n of the corners uf the mouth (8 and 7) ; tor move- 
ments of the forearm and the haTid (6) ; for exten^wu I 
and the forward movement of the hand and iJie arm (S);J 
centers for cmnplex movements of the arms and Ufft^l 
when acting together (2, 3, and 4). 

The ascending parietal convolution presents, from aboToJ 
downward, four centers for complex movements of Uiel 
hand and 'wrist (a, b, c, d), such as the use of individual 
fingers, prehensile movements, etc. At its most superior ^ 
portion, the centers (2, B, and 4), which control the alter- ■ 
nating movements of the arm and leg, as in the act of 
swimming, seem to overlap the ascending parietal conFO> 
lution ; but they ai*e not definitely placed. 

The superior parietal convolution presents the center which 
presides over the movements of the leg and foot ^ as in the 
act of walking. i 

W^hen we discuss the subject of cerebral surgery, reference 
will be made to modifications of the views of Ferrier mlative 
to the motor centers. 

4. The sensorg region of the cortex is confined to the pa- ' 
rietal, tempond, and occipital lobes of the cerebrum. In it 
certain centers have been definitely located by Ferrier, which 
are not, as yet, accepted as fully proven, but many of which 
are now considered as supported rather than confuted by 
clinical and physiological evidence. 

The angular gyrus is said by this author (erroneously, I 
think) to contain the ceniersfor vision (13» 13, in Fig. 26), 
while movements of the eyes also are produced when 
these regions are stimulated,' Later research seems to 

* BipeHmeutd of Ferrier* Yeo, Dalton, ami oibers. 




CORTICAL AREA FOR TACTILE SENSATIONS. 101 

warrant the conclusion that the occipital lobes are alone 
associated with vision. 

The superixyr temporO'Sphenoidal convolution may be regard- 
ed, in the light of existing information, as the seat of the 
centers qf hearing (14, 14, 14, in Fig. 26). The head and 
eyes are caused to move toward the opposite side, and 
the pupils to dilate largely, according to Ferrier, by ex- 
citation of this convolution. 

The centers of smell are now believed to lie in the region of 
the tip of the temporo-sphenoidal lobe (the so-called **su- 
biculum comu Ammonis"). 

The conscious appreciation of tactile sensations is now at- 
tributed to the cortical gray matter of those parietal con- 
volutions which are not included in the so-called "motor 
area'' of the cerebrum. This view has been lately con- 
firmed by the researches of Flechsig, and is in accord 
with pathological facts lately brought to professional 
notice. The view that the cortical fields of motion and 
general sensation overlap each other to some extent is 
fast gaining ground — the sensory area is thought to ex- 
tend over the entire parietal lobe, while the motor area 
does not pass beyond the ascending parietal gyrus. In the 
upper third of these regions tactile sensations from the 
leg (chiefly the opposite member) are probably perceived. 
Those from the upper extremity are transmitted to the mid- 
dle third of the same field ; each hemisphere being con- 
nected with both sides, but chiefly with the opposed limb. 

6. The collection of reported cases of tumors, clots, soften- 
ings, pressure effects (from exostoses, meningeal exudations, 
or thickenings), etc., seems to confer, to a greater or less ex- 
tent, the effects of physiological experiment or faradization, 
and the following general statements as to the results of 
lesionB of the cortex can be safely used as possessing practical 
value at the bedside : 

(a) When the faculty of speeclt is affected, on account of an 
inability to properly coordinate the movements of the 



102 THE BRAIN. 

tongue, lips, and jialate, it is safe to conclude that tie 
lesion involves one of three situations, Tiz. : the anterior 
convolutions ot the " island of Reil," the base of the third 
frontal convolution, or the white substance lying between 
the third frontal convolution and the base of the cere- 
brum. The lesion, being most frequently met with up<»n 
the left side of the brain, will usually be associated with 
some form of paralysis affecting the right side of the 
body ; but the faculty of speech may be affected by 
lesions of the right side as well as those of the left side, 
as proven by the cases collected by Segoin and others. 

{b) Panilysis of motion affecting the upper extremity^ either 
entirely or to a greater extent than other parts involved,* 
suggests a lesion which is situated on the side opposite to 
the pamlysis ; and either confined to, or involving, the 
ascending convolutions of the frontal or parietal lobes. 

{c) Wlien t\\ii facial muscles are prominently affected, I am 
inclined to think the lesion may be located in the frontal 
lobe, anterior to or in the vicinity of the pre-central fis- 
sure or sulcus,* or in the lower third of the ascending 
parietal (convolution. 

(d) Wlien the uiusrlcs of the J eg* are exclusively affected (and 
the probability of sjiinal lesions involving only the lateral 
half of the spinal cord can be excluded), or when the leg 
muscles, in an attack of hemiplegia of clear cranial ori- 
gin, show s])ecial imi)airnient, the lesion can be probably 
placed at the upper end, of the fissure of Rolando^ affect- 
ing the ascending convolutions of the frontal or parietal 
lobes. The views of Ilorsley (page 96) have already been 
discussed. 

{e) Lesions of the sensorg area of the cerebral cortex are 
not as well understood in t\unr clinical aspects as those 
of the motor area, sinct* Irss o])port unity has been afforded 

* See the peculiar typet» of hrnchial motioj>lt<jia and the views of Horstey, as described 
on pages 82 and 83 of this vohuiie. 

' It may not be confined alone to this region, since the various forms of bracfaud 
monoplegia are often associated with facial paralysis. See views of norsley on page 88. 

* See the types of crural monoplegia, descuibcd on pages 84 and 85 of this volume. 



SENSORY EEOIOyS OF CORTEX. 103 

for the pathological study of this type of cases, but many 
facts relating to them have been already stated. The 
reader is referred to pages 88 and 89 for information. 

{f) All of the symptoms produced by lesions of the cortex 
may be the result either of actual destruction of the nerve 
tissue of the cortex, or evidences of irritation of the cor- 
tex. The symptoms will differ in the two cases, so as to 
often assist the diagnostician. 

ig) Lesions of the cortex, if outside of the motor area^ and 
involving the dura mater, may be manifested by convzU- 
sionSj and, possibly, by headache. These convulsions, 
and the headache which may be produced, are respective 
evidences of irritation of some portion of the motor area 
of the cortex, or of adjoining sensory areas. 

(A) The sensory areas of the cerebral cortex comprise those 
of genei-al sensation (pain, touch, temperature) in the 
parietal lobes ; those of sight in the occipital lobes ; and 
those of hearing, smell, and taste in the temporo-sphe- 
noidal lobes. 

{i) The symptoms which prominently indicate irritation of 
the motor cortex are convulsions^ which are often fol- 
lowed by paralysis. This paralysis may be either of the 
transient or permanent variety, although the former is 
the more common. The groups of muscles which are 
prominently affected in the convulsive attacks may afford 
the physician a guide to the seat of the irritation, since 
the same centers are probably affected, as if the corre- 
sponding muscles were paralyzed, rather than convulsed. 

{j ) The destrtictive lesions of the gray matter of the cerebral 
convolutions, if limited to the motor area, produce pe- 
ripheral paralysis of the parts governed by the centers 
which are involved, chiefly on the side of the body oppo- 
site to the situation of the seat of disease. Thus em- 
bolism, by plugging the middle cerebral artery, shuts off 
the blood supply to the center of Broca, and aphasia of 
the motor or ataxic variety will usually be produced ; 
with an accompanying hemiplegia of the side opposite to 



104 



TBF BRAIN. 



the embolus, in case the blood supply is imjiaired 
other parts of the motor area. A destmcdve le:^ioD 
the motor region, if not due to embolism, is liable to \wiA 
diice hemiplegia, without aphasia, on the opposite sid 
to the seat of disease. Paralysis of motion exists tio i 
greater or less extent when the motor area of tlie 
is affected in any part, 

{k) When the paralyzed mnseles become riffidy after an at- 
tack of hemiplegia, fi-om destructive lesions of the motwr 
area of the cortex, it may be considered as an evidence of 
a secandary degeneration of the nerve fibers, which is 
progressing downward along the spinal cord. This is 
prominently developed when the para-central lobule h 
the seat of disease, but it exists to a greater or less ex-j| 
tent when the motor area of the cortex is affected il 
any part. 

(?) We have clinical evidence of the fact that memorte^ of 
various kinds are stored within the cells of the cjorticalJ 
gray matter of the cerebrum, and we are led to the coo- 
elusion that each particular gyrus acts as a receptacle for| 
memories of such impressions as it is capable of receiF-^ 
Ing. We have reason to l)elieve that the occipital lobetl 
appreciate visual sensations and also accumulate sigbtf 
memories ; that the superior temporal convolution ap-j 
preciates souad impressions and retains, furthermore,] 
all memories of sound ; that the motor area of the c&t 
bral cortex has the power of steering memories of mna-l 
cular acts, which are totally distinct from all other formsJ 
of memories ; that smell memories are retained by the| 
cells in the tip of the temporo-sphenoidal lobes, which 
give to us our conscious appreciation of odor \ and that 
memories of tactile sensations, as well as those of pain 
and temperature^ are probably connected with the cells 
of the parietal convolutions, which lie posterior to the 
motor gyri. These facts enable us to draw clinical de- 
dncticms of value respecting those remarkable cases ofj 
word-deqfness and word-blindness which have been 



DIFFUSED CORTICAL LESIONS. 106 

ported from time to time. The inability to recognize 
the meaning of spoken words would indicate an impair- 
ment of the memories of sound ; hence a lesion of the 
superior parietal convolution, in which such memories 
are stored. An inability to recognize written or printed 
language would indicate a loss of sight memories, and 
would therefore point toward a lesion of the occipital 
cortex. Dr. Starr has collected some very interesting 
cases that bear upon this field, and has also contributed 
a popular article upon the mechanism of memory to one 
of our monthly magazines.' 

{m) In those cases where the lesions are diffused over a large 
surface of the cortex (as in the exudation of acute menin- 
gitis, suppuration between the bone and the dura mater, 
etc.), delirium^ convulsions^ and local pain are often 
present, and may properly be regarded as evidences of 
the excessive irritation which exists in consequence of the 
pressure and hypersemia. Coma and paralysis may fol- 
low ; in which case they are to be attributed, either to the 
local ansemia produced by the pressure (thus causing im- 
I)airment of nutrition to the subjacent cortex), or to 
circulatory changes and increased tension of the entire 
brain. 

{n) The aflfection called "diffuse meningoencephalitis" or 
the '* general paralysis of the insane" is so commonly 
met with, and affords such striking evidences of the ef- 
fects of general pressure upon and irritation of the cere- 
bral cortex, that its symptoms have to the neurologist 
more than a clinical interest. From a careful study of 
such cases, we learn that the symptoms first manifested 
are contractions of special fibers in the muscles of the 
face, tongue, and limbs, and that the speech becomes 
tremulous and the articulation spasmodic. Later on, 
acute delirium and impairment of memory and judgment 
appear, and a state of the muscles of the limbs develops 

> " Popular Science Monthly," September, 1884. 



106 



THE BEALW 



which may be one either of semi-paral^'sis or of eemi- 
ataxia. In the final stages, the mental faculties ljec<»iiM» 
abolished ; a state of insanity, characterized by perifii 
of delirium, is produced ; and the patient dies without 
any apparent changes in the ordinary organic f unetioos 
of the body. 

A prominent author, when referring to this subject, 
says: ** A person who exhibits tremors of the facial mm- 
cles, of the tongue, and hand, a vibmtory and alnrred 
speech, angular or tremulous handwTiting, and Lrregn 
lar, small pupils, should be suspected of huAing chrouic 
peri-encephaHtis or paralytic dementia. The addition ol 
a gradual failure of mind — true dementia — makes tlie 
diagnosis certain.''* In case there should be added to 
these above-named symptoms exalted notions, with ma- 
niacal attacks and epileptiform seizures, the case dwerreo 
the name of ** general paresis"; and as such the form ifl 
more usually seen and studied by asylum physicians. 

WEiailT OF THE BRAIN AND OF ITS COMPONENT PABTS, 

The shape of the cranium may be employed to estimate 
the relative development of different parts of the encepha- 
lon; and the circumference of the head and the height of 
the skull above the orifice of the ear may also approximately 
indicate the measurements of the cerebrum. 

The variations in the skulls of the different nations indi- 1 
cate an amount of brain which is in the direct ratio to the 
fiicial angle uf Camper/ The average weight of the brain of] 
a healthy adult of the Caucasian race has been given, by most i 
of the prominent investigators upon this subject-, as about 1 
fiffy ounrfS in the male, and some six ounces less in the 
female/ In the new-lx>m infant, the weight of the brain, 
in the two sexes, is more nearly alike, being in the region 

» E. a Seguin, *• Med. Record;^ 1881. 

" See article by the mithor on the *' Osteology of the Head," ^* Ifedic&I tteoord/' 0oto-J 
bef 16, 1880. 

' See re^earchefi of Ucidf Tiedm^tin, Sims, mid QuAin. 



GROWTH OF THE BRAIN. 



lOi 



eleven onnres for the male cliild and ten onnces for the 
»niale. 

The rapidity of growth of the bmiu is not unifoiin 
iroughout the diffei'ent i)eriods of life. It grows very rajv 
lly iinrtl the age of seven yeara ; then less rapidly \mtil 
le age of forty is reached, when it attains its full develop- 
lent ; after that age it decreases in weight about one ounce 
>r every period of ten years. % 



i ?■ 



^3/ 



5 I 

PlO. 28. — Inferior aspect of tft^ meephnlon, (After Hinchfcld,) 

J I, fttit«T-lor lob« cf the ccn^bmin; 2* iii»h««iio(dttI porii<>D of the po»tcrior lob*; S, S« o^^ 

1 . t 1 i ■ ' nmiiy oi the medUti f1 — * pos* 

him; 7, iintrrior jmtI' r ; 

, . , iia albU^iiitJji; 10, hit . , .. iliir 

U i'ntm cNTfhH ; 12, pons Vftit)|ji ; I a, niiv 

'■■■; 16. olivnnf btjfJv; Ifl, ruf^iifnnii IkmI) (oiijjr 

II, 17, lM»a»plKrvjt of Ibc wreltcllum ; 18, fipi^ure Pi*piirAtiRff 

; t», 10. flmt iitiil fi^cnmi wnvnhilmn* of thf InfrHnr ii»pret oj 

Ig 

in 



108 



TEE BRAIK. 



The comparative weights of the component ji^^^s o^tl 
encephalon are, in approximate figures, about mie ft/tieth \ 
the entire weight for the pons Varolii and the mecliiUa c>bl<rt 
gata, taken together ; one tenth of the entire weight for tk 
cerebellum ; and the balance of the total weight for the in? 
brum and the basal ganglia inclosed within its substanr 
These proportions show a slight variation in the two 8ex»^ 
but not to so marked an extent as to render this statemenl 
far from a connect one. 

It may be stated, as a rale, that the relative proportic 
the cerel>rum to that of the cerebellum is greater in the int€! 
lectual races. The cerebrum is develojied in individuals 
proportion to their intellectual power, although its abfiolcifi 
size may not be taken as a guide to the quality of the niinijj 
since it is undoubtedly true that the brain, as well as tl 
muscular tissue, can be improved, in quality^ by exerci 
That there are important individual differences in the qualilj 
of the generating nervous matter is evidenced by the fact tha 
some small brains actually accomplish more and better wori 
than larger ones ; and that many women often show a highi 
degree of mental acumen than men, in spite of the fact tl 
they have brains which are lighter in avoirdupois. 

From a most carefully prepared table of the weight 
brain substance possessed by men of renown as intellectua 
giants, as well as those which revealed an unusual develo] 
ment of bmin after death, contained in the work of a promi 
nent author,' some interesting facts are revealed. 

The heaviest brains* on record (where the statements 
to be relied upon) were possessed by an Indian squaw, a ooi 
genital iml)ecile, and an ignorant bricklayer, both of whom 
outweighed Cuvier and Abercrombie ; while a boy of thirteen 
years of age had five ounces more brain than Webster ani. 
Agassiz. Such a table shows the utter absurdity of attempt 



» A, Flint, Jr , "Text-Book of Physiology.*' D. ApplcUm k Co.. New York, 

' Congenital imbecile, i^ri?d thirty, 70J ouner^ ot bniln Fubstanco ; hrickUyer, €7 

otmces; CuTier, 041 ouncoi; Al>ercrombie, 68 ouoees; WoWtir, h^ ounces; Ag«5«ii, 

9B| ounoei. 




WEIGHT OF THE BRAIN. 



109 



dg to apply to individuals the rule that the greatest brain 
)wer is po.ssessed by the one having the gieatest amount of 
>rain substance. 



\i5 



i'SS 



AU 



l?38l 



Pia. 29. — ConvoUtioHM &n th* initfmal aupcH oftke hemuphfret. (After Sappey,) 
J, fronUl lotie; 2, 0[ihcnotdal lobe ; 8^ 3, oonvolutiou of iht- corpus (^llo^um; 4, -1, convo- 
|utUm<i fortu»ii._- tho niUMl** group of Uh' intt*rn»l eurfiiL'r ; f», ft, cnnvolutinriH of t\w 
nti * I m^ of tlie ; 'jup; 7» t^nl' ' he mld- 

iM 8, wiilcu- tlic niucri' irroup; 

U, , ,r .- ^ n^j-iimi; in, ^* ,,,, ,-i ilut' wrpus L.il,- ...i, , , ,, ,. -mjni of 

Th' ■ im; I'Z, ^)0:J,tiiiior eJHrrij/ity of the corpus eallosum; Itt, fornli; 

11, ' ' ' fcirnix; l^i, left uiiti*noi ituh of ilii' fornix, pti,<wijifi into llic intcf- 

tial wntl 111 the oplio tliiiUtrniN, tu n>Mcti tUu rnrri'tifMmdinir corpus a1hu>»ttfc»<^Lrour»e 
itiJk'aM l»if a dotted lifU' ; li). foraiiicn of Mutirti; 17, tx>rf>MB uihicann, In wlikih lUc 
interior cniu of tho fornix bends* upon itf«clf» in ibc fonn of n flgnre of eight, lo be 
lost in the iiubstaitce of the upiie thiihiritu«; IH, i*eptuni hioidutn ; It*, Biyetion of the 
e!; ' ^ •'- • ' ' 21, left mipi'ikir yndiiiHlo of r. Tl, i^eo- 

li tliinJ Vi»ntiirk' ; lifi, tobertntlu <[i , nboVC 

Tiw ,,, - , ^ ^vlth it? inferior piiluru-le Hod \l. | i^ii'um- 

mlflwirr ; *i4, Jk»ctinn ot the ttnterinr commtHsurr ; LTi. niiucdnot of S> Iviut^ ; L'ti, wctioq 
of lite viilvif of Virti»«icn«; 27, fourth v«ntricic; 2^, 28, «eel](n of the tntddle lobo 
of lli« ccfcbellnm , 21t», artwr ritjn ; 'd*\ eorpu;* djiercum ; HI, pUuiiary bwiy ; 82, optic 
M ^3* P^i^' VftfolH; Z4^ iiiedutU obloni^ta* 



EFFECTS OF IXTRA-OEREBRAL LESlONa 
Th« physiology of the ffreai ganffJia of (he cerebrum is 
far from being satisfactorily determined, since the expcri- 
Dientfl of different observers uppurt^utly prove most glaring 
conrnidi(*tiona It is, liowever, prohnhle that the two snbdi- 
vi?«ion5* of the roriHiM sfriitum itln* rraidate and the lenticular 



riiir -jj- 




no 



THE BBAIX, 



nuclei) hare motor functions of a character wTiich are not y^t 
positively decided, while the attributes of the optic thahunta 
are still involved in more <:»r ks,s obscurity/ 

It can safely be considered as proven that the anterior 
pair of the corpora quadriffejnina {the nates) are in some w 
concerned in the special sense of vision, and belong to rlw* 
optic apparatus, although the motions of the eyeball 8ee^ t<» 
be more dix-ectly influenced than vision itself. The posterii^^ 
pail' are probably functionally associated with the coanlina^ 
tion of muscular movements. The fibers of the lemnis^ 
cus or fillet-tract can apparently be traced in pai't to these 
bodies- 

The internal capsule of the cerebrum seema to be Oiie 
of the most important regions of the brain, from a ollnlcaJ 
standpoint, since the slightest pressure upon the fibers 
which it is composed prodnces symptoms which Viuy wii 
the portion pi'essed upon* A secondary deffencraiion^^ whi< 
descends along the nerve fibers of the eras, pons, medill] 
and spinal cord, is inevitably the result of disease of 
portion of the cerebrum. 

If the region occupied by the pj/ramfdal tracts be tJ 
seat of pressure or disease, pai'alysis of motion^ chiefly con- 
fined to the opposite side, results; if the sensory tracts 
affected, a condition of amrsthesia of tlie opposite side 
produced. Choreic movements^ which vary in degree 
type, and which mny appear as athetosis, ataxia^ true ohoi 
or tremor, are sti-ongly diagnostic of lesion of the intemi 
capsule, provided they follow an attack of hemiplegia 
hemi-amestheaia. 

Lesions of the parts adjoining the irUeriial capsule {th< 
caudate nucleus, the lenticular nucleus, and the optic thals 
mus), if the seat of haemorrhage, tumors, or other condition 
which are capable of causing pressure upon it, may produi 

' To what eitent Ibifl ji^aiiglion prcuidea over or inBaenoet ieoflory perceptions rrn 
I consiilerHl unsettled. For opinions on the subject^ Uie reader \» referred to a mibifto 
at page of this voluiue. 

* For the effeeta of tbld d&«iceadmg type of secoDdar^ degenermtlon of Tk^nre 
■ee a flubfloquent page of ihia toIuiuc. 




8UR0ICAL GUIDES TO CEREBRUM. HI 

symptoms similar to those of disease of the internal capsule 
itself. 

When the central portions of the cerebral hemispheres 
are the seat of some type of disease which has been suddenly 
developed, as in haemorrhage, acute softening, etc., symptoms 
rtferabU to the optic apparatus are usually present, in addi- 
tion to the other symptoms which have been given above. 
Thus, the eyes may be turned away from the paralyzed side, 
and, therefore, toward the seat of the lesion ; the head also is 
often similarly turned ; and, in case the injury done to the 
brain is severe or extensive, a very marked rise in the surface 
temperature of the body may be observed. 

When the pressure upon the central portions of the 
cerebral hemispheres is gradual^ as in the case of growing 
tumors, we have developed certain special signs, which de- 
pend upon the situation of the tumor and the line of its 
greatest pressure ; but we are also liable to have changes 
develop in the eye— those of " neuro-retinitis "—which may 
result in the condition known by ophthalmologists as the 
"choked disk." 

THE SURGICAL BEARINGS OF CEREBRAL TOPOGRAPHY. 

In the year 1861, Broca invented a scientific method of de- 
termining the relations of different parts of the cerebrum to 
the exterior of the skull, which consisted of driving pegs 
through the skulls of animals and of cadavers, holes having 
been previously bored through the bone in order to prevent 
fracture and injury to surrounding parts. The skull-cap was 
then removed with extreme care, and the convolutions which 
were wounded were thus determined. It was discovered by 
this observer that the fissure of Rolando^ whose relation to 
the coronal suture was then unknown, lay obliquely, and that 
Itfl upper extremity could be placed, with great accuracy in 
man, at a point situated 40 mm. behind the coronal suture. 
It can also be located at one half inch behind the central 
I>oint of a line extending from the root of the nose to the 
oodpital protuberance. 



THE BRAIX. 

This fissure i^^as particularly stadied ,on account of it5i«- 
lation to the motor rtfjlou of the cortex^ and its exact beariJi| 
to the exterior of the skall was therefore of ^reat inipcirtaooe'. 

The same observer was also able to pmra that the cxi^rml 
parietooccipital Jissure of the cerebrum lay under the tomb 
doid suture of the cmniura. In 1873, the experir 
Heftier and Bischoff were added t<> those of Broca, wLmr- i .i* 
ner followed with his I'esearthes in 1874 and Fere in 167i 
The drawings which Turner furnished were admirable in their 
way> but are, to my mind^ hardly adapted to the puriMx<iesi o( 
the surgeon, since the guides which the bony prominence o( 
the skull afford are nut brought into such proniliience as tfi 
be readily comprehended by the casual reader. If the sur- 
geon is to utilize the valuable researches of the inrestigators 
above named (and several most brilliant surgical opemtiail 
have alreadj^ been performed from the light which the new' 
acquired knowledge of the topography of the cerebrum li 
afforded), certain bony prominences of the skull must be di 
ignated, aa of importance, as guides to the special con vol 
tions and fissures of the brain. Now, there is one line whii 
is easily drawn upon the head of the living subject (the alv 
olo-condylnid plane of BrocnX upon which perpendicular I 
may be descril»ed, intersecting certain bony pointss whirl 
lines can be utilized a^ guides to parts whose situation is no 
positively known. This base line should be a stmi^ht oni 
and should intersect the tip of the mastoid process and 
line of the cusi>s of the teeth of the upper jaw,* 

This is the natunil ba.se line of the human skull^ when t 
lower jaw is ivmoved ami the skull placed upon a table 
hence it is a plane admirably adapted for the study of 
guides (which will W giveuK upon the skeleton, in the offii 
of each practitioner, pnniou5 to an o|)eration. Furthermore, 
a skull can Oiunily Ih^ iminttHl upon its exterior so as to b; 
the lint^, designate<l lui im|H)rtant> inte prominence, and 

* ThU Aiiibor fiUcwi iHv lllM» M ^ntf^rt^cUiMZ Ibt tfin^^ •^lAf owfpM homt; bat, «• 
Qil» (till not l>« |(p1i In ih» U?ii^ *tiU|H,t» «ii>.l «« H oorTO«|wn<b to Ibe tip of tlic mu^imi 
p^t^e^, I hftvc fnodIM III* ftM$ to M lo iAiii|4tl^ Im tiael dtwOon tttK)o the i^xKHor 
of iht ikiia 



±^ 




iHiii| I 




SURGICAL GUIDES TO CEREBRUM. 118 

assist the surgeon in the review of those points which pos- 
sess si)ecial value. The contributions of F6r6 and Horsley 
are, to my mind, the best of all the authors named, since the 
points most needed by the surgeon in a practical way are 
given. A resume of F6r6's guides is so tersely and clearly 
stated by Seguin that it would be useless to attempt to im- 
prove upon it. It will be perceived in the plate, introduced 
to make these guides more clear than a mere verbal descrip- 
tion, that the line described, viz., the alveolo-condyloid plane 
of Broca, is used as a base line upon which to erect perpen- 
diculars at distances which can be accurately measured upon 
it ; and that these perpendicular lines intersect certain regions 
which, from facts previously recorded, are of the greatest 
importance. I quote the resume of Seguin ' upon this special 
department of cerebral localization : 

"1. A vertical line (a) drawn from the alveolo-condyloid 
plane, through the external auditory meatus upward, will 
pass through or very near to the bregma, or line of junction 
of the frontal and parietal bones at the vertex ; it passes 
through the anterior (lower) extremity of the fissure of 
Rolando. 

"2. If, from the upper end of this vertical line a, we meas- 
ure a distance of 45 mm.* backward toward the occiput and 
draw a descending vertical line (1-2), we mark out the loca- 
tion of two most important parts of the cerebrum, viz., the 
I)Osterior extremity of the fissure of Rolando [at 6], and the 
I)08(erior limit of the thalamus opticus in the hemisphere 
[at c\. 

"3. To conclude with the occipital end of the skull ; if we 
can make out with the fingers the lambdoid suture at the 
median line, we thus learn the situation of the subjacent 
occipito-parietal fissure, which separates the parietal and 
occipital lobes. 

"4. The last vertical line worth noting is one drawn at a 
distance of 30 mm. forward of the anriculo-bregmatic line. 
This vertical line (3-4) will pass through the middle fold of 

* ** Madkal Record,** 1878. * A millimetrc is about one twcnty.fifth of an indi. 



114 



THE BRAISL 



the third frontal convolotion (just forward of the speech cen- 
ter;, and will also indicate the anterior Innit of the central 
cerebral ganglia, viz., the head of the nacleiis caadatns in 
the hemisphere [at d]. 




Fig. 30. — Ouiline of ikul! retting upon the cUreoia-etmdjfloid plane of , 
from TopinardV ** Anthropology " by Segmn.) 



(yoffified 



V.rtical line a, or auriculo-brtgrnatic. Lin** 9-10^ drawn parallel to the plane of Broea 
Upon this line, at a distance of 45 mm. posterior to the bregma, a Tertical line, 1-2, 
will pass thnjur^h the upp<'r 'inner) end of the fissure of R<3andoi, 6, 6, and through 
the posterior extremity of the thalamus opticus (c\. A third Tertical line, S-4, drawn 
at 30 mm. forward of the bregma, will pass through the fold of the third frontal 
gyrus (a), and throufrh the head of the nucleus caudatus (</). The horixontal line, 
7^, at 45 mm. below th«- bregma (scalp), indicates the upper limit of the central 
gan;ilia. The third horizontal line, 5-6, passing through the external angular pro- 
cess of the frontal bone and the occipito-parietal junction, approximately indicate! 
the course of the fissure of Sylvius, and corves for measurements. At 18 or 20 mm. 
behind the external angular process on this line is the speech center of Broca ; 6 to 
8 ram. behind the interst-ccion of 3—4 and 5-6 is the bi'ginning of the fissure of Syl- 
vius, and at 28 or 3«» mm. behind this intersection is the lower end of the fissure of 
Rolando, 6, 6, placed a little t(X) far back in the cut. At x (near 6), near the median 
line, is the location of the occipito-parietal fissure. S, the stephanion ; P, the pierioti. 
These two parts will be discussed in a subse^iucnt page. 



**o. The upper level of the central cerebral ganglia may 
be quite exactly indicated by a horizontal line drawn at a dis- 
tance of 45 mm. below the surface of the scalp, at the bregma, 
(or 35 below the surface of the bare skull at the same point). 
This line (7-8) also runs across the middle regions of the mo- 
tor district of the convolutions, containing centers for the fece 
and upper extremities. 



8UR0ICAL GUIDES TO CEREBRUM. 115 

"6. The external angular process of the frontal bone, not 
diflScult to define in the living subject, is the starting-point of 
another horizontal line (5-6), whose posterior extremity passes 
a little below the lambdoid suture. Upon this horizontal line 
we can, by measurement, determine the location of certain 
parts. Thus, at a distance of 18 or 20 mm. behind the exter- 
nal angular process, lies the folded part of the third frontal 
convolution (a). This point, in many heads, will correspond 
to the vertical line 3-4. 

'' 7. The situation of the fissure of Sylvius may be approx- 
imately ascertained in the following manner : Its middle por- 
tion extends horizontally, almost under the upper part of the 
squamous suture, which in the living subject is to be found a 
little below the horizontal line 5-6. The anterior extremity 
or beginning of the fissure of Sylvius is a little below this 
horizontal line, at a distance of some 5 to 8 mm. posterior to 
the intersection of 3-4 and 5-6, and consequently about 22 or 
26 mm. anterior to the auriculo-bregmatic line a. Lastly, 
according to Turner, the parietal eminence almost always 
overlies the supra-marginal gyrus (P*, Pig. 20), consequently 
the i)osterior extremity of the fissure of Sylvius is likewise in 
this vicinity. 

"8. The angular gyrus is to be found below and behind 
the parietal eminence, a little above the horizontal line drawn 
from the external angular process (5-6). 

" 9. The anterior (lower) end of the fissure of Rolando lies 
at a distance of 28 or 30 mm. behind the line 3-4, and a little 
above 5-8. It is, therefore, a few miUimetres anterior to the 
vertical line a." 

With this plate as a guide, and with a thorough knowledge 
of the facts comprised in previous pages of this chapter, it is 
not out of the bounds of possibility to definitely locate the 
existence of lesions in certain poitions of the human brain, 
to map out their situation upon the exterior of the skull, 
and to reach them with surgical means of relief, provided the 
case be one which would justify such a measure. Broca has 
been successful in trephining directly over an abscess of the 



116 



THE brain: 



third frontal convolution, wliich was suspected, SiiccessfQl 
cases have been reported of trephining of the sktili for fj 
ments of the inner plate which were rompres,»dn]^ the 
cending gyri of the frontal and parietal l<»Ijes, thus caoji 
paralysis. Turaora of the brain have lately been located a< 
curately and removed by the knife and trephine. 

Horsley has lately added a valuable contribution to tbe^ 
subject of cortical localization, based upon experimentati' 
on monkeys, and also on observations in ten cases wheit? t 
diseased area was successfully determined in the hnraan 
subject prior to operative procedure. His eoiiclnsirms are 
therefore worthy of note. They may be summarized as: 

1. 8ulci\ or fissures^ are not to be regarded as a^cvurale 
boundaries to cortical areas^ although they constitute valu- 
able landmarks for operative procedures uprm the cortex, 

2, The motor centers^ according to this observer, ai^ capu* 
ble of further sithdimsion than those described by Ferriefi 
and they overlap each other at their borders. 

3. The face area^ taken as a whole, embraces the l 
third of both centml convolutions (4 and 5 in Fig. 22). Tlii 
is subdivided into (a) an u^iper and anterior portion, whici 
controls tlie upper part of the face and the angle of the month 
(b) the anterior half of the lower portion, which governs the 
movements of the vocal cords ; and (c) the posterior Jialf 
the lower portion, which governs the lower part of the 
and the floor of the mouth. 

4, The area for the upper limb occupies J.he middle third 
of both central convolutions, and also the base of the superic: 
and middle frontal convolutions. It joins, and also mer^ 
with, the area for movements of the head and neck in t 
middle frontal gyrus, and with that of the leg in the sui>eri 
frontal gyrus. 

In the area described as pertaining to the npi>er limb, th 
uppermost part is thought by Horsley to control the musci 
of the shoulder ; below, and posteriorly, the elbow is rep: 
sented; stiU fuitlier below and somewhat anteriorly, the 
wrist ; next in oixler, ant€riorly, the finger-movements are 




£ao9 



I 



Special Cortical Motor Areas of the Human Subject. 

(According to obeervationR of Iloraley and Beevor.) 




Area for the thumb. (Horeley.) 



Combined STnchronous moTements of both 
limbs. (Horaley.) 




The lower Umb. H. Aret for the big toe in Are* for movementH of the head and neck, to- 
tlw para^oeBtral lobule. (Beevor and Iloni. gether with conjugate deviation of the eyeo. 

ley.) (Horsley.) 



SURGICAL GUIDES TO CEREBRUM. 117 

placed ; and lowest of all, and posteriorly, the thnmb-move- 
ments are located. These views he substantiates by observa- 
tions made in cases of cortical tumors, where spasm was 
developed and appeared first in an isolated region of the 
upper limb. 

5. The area for the lower limb is described by this ob- 
server as embracing the upper portions of the two central 
convolutions ; also the whole of the superior parietal, the 
base of the superior frontal convolutions, and the para-central 
lobule. This description is not materially different from that 
of Perrier (Pig. 26). 

The subdivisions of this area are as yet incompleted, but 
the points given are of interest to the surgeon. The move- 
ments of the big toe are referred to the para-central lobule ; 
those of the leg alone to the middle part ; those of the leg 
and arm combined to the most anterior portion. Most of 
these conclusions agree in the main with those of Perrier. 

6. The area for movements of the heojd and neck^ and also 
for conjugate deviation of the eyes, is placed by this observer 
(in common with Perrier and Munk) in the bases of the three 
frontal gyri (see 12 in Pig. 25). 

7. Respecting the steps required to locate the fissures of 
Rolando and Sylvius upon the human subject during life (as 
a basis for surgical procedures), the following conclusions are 
reached: 

(a) The method first described by Prof. Thane for locating 
Rolando" 8 fissure is adopted. A careful measurement is first 
made along the mesial line of the skull, starting from the root 
of the nose and extending to the occipital protuberance. 
This distance is then halved. The fissure of Rolando at its 
upper part lies one half inrh posteriorly to its central point. 
A strip of flexible iron (with a movable arm placed at an 
angle of sixty-seven degrees to it) is now laid upon the middle 
line of the head, the point of junction of the movable arm 
with the mesial strip being carefully located at the point 
previously determined as overlying the upper end of Ro- 
lando's fissure. When this is accurately done, the movable 



TEE BRAIN. 



arm marks the course of the upper two thirds of the fii 
of Rolando, but, as the h3wer third tends tu bend sliglitlyl 
backward, it does not as clearly define the lower third of ilul] 
fissure. 

(&) To accurately locate the fissure of Sylvius apon tb 
skull no little javcision is requii'ed. A few points in the 
bones of the skull have first to be accurately determined. 
These are as follows: (1) The point where the tcniixinil ridgi? 
crosses the coronal suture (the "' stephanion^}. This can 
usually be felt with the finger, the coronal 8Utare uppe^ng 
to the touch either as a depres.sion or as a ridge lying between 
two grooves. (2) Exactly midway between the stepbaniuQ 
and the upper border of the zygoma, on a line drawn verticil 
to the zygoma toward the stephauion, lies another jk): 
known as the ^'pterfon.'^ (3) To determine the hiyheait poim 
of the suture which exists between the squamous portion ol 
the temporal bone and the inferior border of the panel 
bone (the ''' squamoparietal" suture), a measurement baa 
be made, because that suture can not be felt beneath tbi 
temporal muscle. 

In front of the temporo-maxillary articulation, an uprigb 
upon the line 4-2 in Fig. 30 would cross the zygoma, Thaj 
junction of the upper and middle thirds of the measureinenU 
made upon such a vertical line between the upper border of the 
zygoma and the ridge formed by the temporal muscle, indi- 
cates the situation of the highest point of the squamo-parietaliB 
suture. ^ 

The anterior limb of the Sylvian fissure starts from a point 
which lies from one half to one line (one twenty -fourth to«| 
one twelfth of an inch) in front of the "pterion/* It rani 
anteriorly and upward from that point. The posterior limb 
passes backward and slightly upward from the same point ^ 

8. The sulci of the fro7iiaIloljt\ and also the inter parietxd^k 
sulcus (which limits the so-called *' motor area*^ of t\ie cortex 
posteriorly), are next to be located upon the exterior of the 
skull, in order to map out the convolutions. The guides to 
the sulci are as f oUows : 



I 




nORSLET'8 VIEWS, 119 

The precentral svlcus lies somewhat behind the coronal 
suture and parallel to it. It extends to about the middle of 
Rolando's fissure. 

The ivferioT frontal sulcus diverges from the precentral 
at about the level of the temporal ridge. 

The superior frontal sulcus starts at a point in the pre- 
central gyrus somewhat posterior to the line of the precentral 
sulcus if continued upward. The exact point is about mid- 
way between the fissure of Rolando and an upward continua- 
tion of a line in the direction of the precentral sulcus. Its 
altitude in the cerebrum is slightly above the level of a point 
(midway between the mesial line of the skuU and the center 
of the parietal eminence) which designates the lower limit of 
the sui)erior parietal convolution. 

The inter-parietal sulcus in its ascending course starts 
from a i>oint on a level with the junction of the middle and 
lower thirds of Rolando's fissure. It turns backward on a 
level situated midway between the mesial line of the skull 
(marked by the longitudinal fissure) and the center of the 
parietal eminence. 

There are certain suggestions, which may be thrown out in 
this connection, which are safe ones to foUow in cases where 
the propriety of surgical relief is called in question. These 
may be stated in the form of propositions, which are of neces- 
sity based upon the contents of the previous lectures. 

1. If the injury sustained (provided the case in question 
be one of a traumatic origin) be situated over the motor area 
of the cortex, the presence of ancesthesia in combination with 
motor hemiplegia is a contra-indication to attempts at sur- 
gical relief. This symptom (ansesthesia) probably indicates 
some injury to the sensory fibers which enter the posterior 
third of the internal capsule ; hence the lesion is probably 
too extensive to be relieved by trephining. 

2. If the sensory region of the cortex be involved, and 
paralysis or convulsive movements occur, an operation is 
contra-indieated ; since the lesion has probably been so ex- 
tensive as to extend to the motor area, or has involved or 



aimpreiwcid Ibei 



I at a poiiit remor ed tram tim i 



3* The occnrreon at paraiyHs on tke 



wMch the 



reeeired is always 



'onrrB'tDidiGi* 



tojuy 

tiaD to aof surgical prooedare at the aeat of injury ; siiice H 
pfot^ably indicates some lesioo of the opposile side, donbtlM 
dependent apon tranaiB]rt€^ force {eantre-wupy 

4. The rampldenets qf the paralyM may be often taket 
afl a guide to the amcnint of injury done to the oerebnim : if 
the paralyiM be rery profufind, the chance of sueress frtMi 
trephining is mctreinely small, since the injury has prol 
affected parts deeper than the crirtex. 

5. The appearance of paralysis of any of the ftp 
nerfffH of the eranium^ or the derelopment of the ««yinp|i« 
due to lesions of the base of the brain or of the ba$a] ganj 
8uch a* the Cheyne*8toke9 respiration,* chaked diak, an 
vomiting, may l)e regarded as contraindications to siirgic 
interfen^ncB, 

G. When an injury to the skull is followed, after a laj 
of some weeks, by the ataMc form of aphasia^ the diagno8ta_ 
of abscess of the base of the third frontal convolution^ or 
slbly involving' the island of Reil or the white substance sit 
ated between the third fmntal convolution and the basis < 
the cerebrum, may be safely made.* In such a case the oper 
tion of trejihining, as performed by Broca, affords a sir 
probal>ility of relief. 

7, Cases of injury which are followed immediaiely ft| 
ataxic or motor aphakia are sti'ongly diagnostic of either ^ 
spicula of bone or the pressure of a clot in the neighborhc 
of the center oi Broca, The former condition would be strong'! 
ly in support of surgical interference, since it would probably 
continue to ci^atp pressure or irritatirui until removed, while 
the pressure of a clot might also be relieved by trephining. 

' A respintion wboto rhrthm ^tp^tliljr incT««Bcs, ud then dccrcftM«, io « i 
I i»r tltfif ; d«MTllt0d in 1^1^ by Chfynr. nnd by fiUikci b 1816. 
* Auttioritic« are not •U in lu'conl iiitb thb etelcnifiit, Tbc fttithor hfti dli 
oonilitioni known m ** word^blindtiii* " md ** vord-d«nlh«M** is preYionf |ni^ 



INDICATIONS FOB TREPHININO. 121 

8. If the region over the fissure of Rolando be subjected 
to apparent injury, and the symptoms of some of the special 
types of monoplegia appear (affecting the muscles of the face, 
arm, leg, or any of these combined), or even the occurrence of 
a slight form of hemiplegia follow, successful results from 
trephining may be reasonably expected. The presence of 
anfiesthesia, as before mentioned, would, however, still be a 
strong contraindication to such a step, since it would prove 
that the lesion was probably of too deep a character to be 
benefited by the simple removal of a button of bone, as the 
posterior third of the internal capsule would probably be 
found to be impaired. It must be also remembered that the 
motor paralysis, of whatever kind it may be, must be confined 
to the side of the body opposite to the seat of injury, if benefit 
is to be expected. The type of monoplegia which exists may 
often be used as a guide to determine the extent of the lesion 
as well as its situation. 

9. Convulsive attacks, which invariably begin by spas- 
modic movements of some special locality of the hody^ and 
whose cause is» apparently a cerebral lesion or a traumatism 
of the head, may be treated successfully in some cases by a 
trephine over the motor center of the part which is primarily 
attacked with spasm. 

10. Homonymous hemianopsia (when uncomplicated) points 
strongly to a lesicm of the cuneus. Trephining has been suc- 
cessfully performefl over this region of the occiput for sus- 
pected tumor, whose presence was revealed by this symptom 
alone (Seguin, AVeir). 

DIAGNOSTIC SYMPTOMS OF NON-CORTICAL LESIONS OF THE 

CEREBRUM. 

Many of the clinical facts pertaining to non-cortical cere- 
bral lesions may be thus summarized : 

Prqfound coma is more often encountered in non-cortical 
lesions than in cortical, iK)s«il)ly because the cerebro-spinal 
fluid is more liable to be displaced from the ventricles 
(Duret). 



123 



TBE URATN. 



Hemiplegia coramonly exists in combinatian tmm mortf!f\ 
less heviiancBsthesia^ and paresis of the lower pari of th\ 
face. These symptoms are observed, as a rule, upon the sid^j 
of the body opposed to the cerebral lesion. 

ParUy when present in the head, is less circiimHcritied thas I 
in cortical disease, and is not increaaed by percussing* or eli* 
cited by that step when absent. 

Muscnlar rigidit/y in the paralyzed mnsrles develops late. 
Typical monoplegia is probably never observed. 

Tremor^ hemicharea^ and athetosis are not nneonunoi 
sequelae of non-corrieal cerebral lesions. 

The senses qf sight, smelly hearing^ and tactile sen^ibilUf 
are occasionally impaired to a greater or less extent by non-| 
cortical lesions. The seat of the lesion will modify the evi^ 
denees of such irapairment, because the tibere of some of 
cranial nerves may be involved by the lesion, while otheis 
may escape injury* 

Typical attacks of Jacksonian epilepsy do not occur/ 
though general couculsions may be excited. 



THE CORPUS STRIATUM. 

Two nodal ma.sses of gray matter, situated within 
substance of each cerebral hemisphere, have been referred 
in previous pages as the *' basal ganglia." They api)ear, froni 
their situation and relation to the radiating fibers of the cere* 
brum (Fig. 7), to be the '* naturally appointed guardians" 
which preside over all impulses transmitted to or from the 
cerebi'al cortex. 

Physiological experiment seems to point clearly to an 
automatism in the cells of these masses, exhibited chiefly in 
the mairtfcnajice of equllihrium after the hemispheres luive 
been removed. They seem also to exercise some discriminat- 
ing power over impulses which are forced to pa^ through 
them when the hemispheres are called into action. 

From an anatomical standpoint these bodies seem, as 
Luys states, to be the *' poles around which the nervous 
elements of the cei-ebrum gravitate"; and to constitute **a 



I 



I 



THE CORPUS STRIATUM. 



123 



crown, as it were, to the fibers of the crusta and tegmentum 
cruris "(Fig. 7). 

The corpus striatum is the anterior of these two bodies ; 
and the fibers which are apparently associated with it (the 
basis cruris, Fig. 8) can be traced into the antero-lateral 
columns of the spinal cord, with the exception of those that 
are supposed to pass to the cerebellum through the medium 
of the pons. It may be considered, therefore, as the probable 
seat of modification and reinforcement of motor impulses ema- 
nating from the cerebral cortex. 




Fio. 81. — Antero-potterior vertical section of the right hemisphere, showing the cavity of 
the lateral ventricle. (After Dalton.) 

C, oorptif ftriatum; S, eurcingle of same; Y, yentricle; A, amygdala; 1, interoal pa- 
rieto-oocipital fissure ; 2, calcarine fissure. 



In the fresh brain the corpus striatum appears as a reddish- 
gray mass, situated in front of the optic thalamus in each 
hemisphere of the cerebnim. Its large extremity is directed 
forward, and it gradually tapers as it is prolonged toward 
the jKisterior lobes of the brain. It is abundantly supplied 
with capillary vessels, which circulate within its substance. 
The extreme softness and friability of the mass are largely 
due to this fact. 

We know, clinically, that the larger proportion of extra- 
tHZsations of blood within the cerebral hemispheres affect the 
corpus striatum ; and we may reasonably attribute the greater 



124 



TEE BRAIX. 



f!*equeiicy of unOateral paralysis of motion, as eompa 
those of sensation, posmbly to this abundance at vessei 
the non-remstant character of the surround iujLC brain 
stance. 

The temi '* corpus striatum^ is apparently n.sed by 1 
in his late work upon anatomy, to cover the eutidiite iii 
lenticular nucleus and also the internal capsule of the c<*i 
brum. Rosenthal includes the caudate nucleus and the cami 
lenticular portion of the internal capsule under this term, bi 
he treats of the lenticular nutleus as a separate ganglio] 
Meynert applies the term to the caudate nucleus alone* Di 
ret divides the lenticular nucleus of most authora into t 
nuclei, one of which (the posterior or brownish-i'ed portioi 
he calls the ** lenticular nucleus/- and the remaining porti 
the '*gray nucleus/' im account of its lighter color. 

The entire mass of the corpus striatum, when viewed aft 
the removal of the hemispheres by a horizontal cut 
above the level of the basal ganglia, presents an ovoid pj 
form appearance, the larger extremity being directed towai 
the frontal lobe, and the tapering end investing the optic rha 
amus (which lies behind it) as a layer of reddish-gT^iy mi 
ter of steadily diminishing thickness. Tliis ^'taiMlke" pn: 
longation (the cauda) has been described by Dalton ' (wb 
in common ^\ith several other observers, has investig;ited i 
peculiarities) as forming a complete ''surcingle" to the thal- 
amus. Vertiro-transverse sections of the hemisphere of t 
cerebrum, made to include the thalamus (as sln)wn in Pig. 1 
reveal two cuts of the caudate? portion, an upper or ventrir 
lar portion, and a lower portion which is perceived in the 
region of the gyrus hippocampus (the avjygdnla). Such a 
section shows, moreover, that the so-called 'Mntemal ca 
sule"of the cerebrum divides the corpus striatum into tw 
distinct parts; one of which has this tail-like pmlongarion 
and projects into the lateral ventricle (the caudair nneleui 
or ventricular portlan), while the other is shaped soinewl 
like a section of a lens, and lies buried within the subst 

> Gmtiolet, Qir^hieM, ind Todd oooflrni tliis view. 



al- 

I 



^ 




THE LENTICULAR NUCLEUS. 125 

I of the hemisphere (the lenticular nucleus^ or extra-ventricu- 

\ larportiony 

The caudate and lenticular nuclei become fused, however, 
both anteriorly and posteriorly. In front, the caput dips 
downward toward the region of the base of the brain, and 
becomes fused with the third division of the lenticular 

. nucleus (the ''olfactory district" of Gratiolet). Behind, the 
Cauda becomes joined to the temporal process of the third 
member of the lenticular hucleus {pedunculTis nuclei len- 
ticvlaTis\ near to the amygdala. 

Structurally considered, the corpus striatum seems to be 
composed of nerve cells of two varieties : one being of large 
size with many processes, and the other of small size and 
multipolar.' The small cells predominate over the large in 
point of numbers. It seems probable that the fibers destined 
for the spinal cord are associated with one set of cells, and 
those to go to the cerebellum with the other (Luys) ; but this 
statement is as yet somewhat conjectural, although Meynert 
believes that it is supported by anatomical research. 

The NUCLEUS LENTicuLARis is shaped somewhat like a 
wedge, its base being directed toward the frontal lobe and 
the island of Reil, while its point passes into the "crusta" 
(the ha^is cruris of Meynert), and terminates posteriorly in a 
jagged, thin edge. 

If a section through its substance be examined, the micro- 
scope will show the existence of two sets of nerve fibers within 
it, viz., one, whose direction corresponds to the general 
course of its longest axis, or from base to apex ; and a second, 
which runs parallel with its curved base.' 

* The resder is referred to Fig. 32 and other diagrams incorporated in the text of 
this woi1[. 

' These oelli rary from 80 /a to 15 /a in length, f/f^j^ millimeter. 

* The fibers of the lenticular nucleus which run parallel with the curved base of the 
wedge separate the three diTisions of the ganglion. The extra-ventricular half of the 
ooqNis striatum must be regarded as connected especially with the fibers which arise from 
the istand of Reil and other parts in the vicinity of the walls of the Sylvian fissure. Its 
form Mggcsti that the frontal and parietal lobes furnish by far the forester number of its 
fibers, as oontraated with the temporal and occipital. It is worthy of remark that the 
fibers which pass through thb ganglion do not take a direct course, but describe compli- 
etled ipiral Unea. 

11 



126 



TffE BRAIN. 



The second set divides the ganglion into three dlM 
7nembers (Glieder), the external being the thir^ker and \MpL 
while the two inner are the richer in medullary fibers, wl 
gives them the name of ^^ ghtbus palUdus^^ (^^K- ^)* 

Within the substance uf the oafdate Nuci-Krs (ml its 
ferior and internal ptirtion), there exists a ma^s af yello' 
colored matter to which the name ^^ yelUyw nurlea-.s ■* has 
applied by Liiys. In it, the smaller cells of this ganglion an 
described as being very abundant, while the processes |^f6i 
off from them ai'e of extreme tenuity. There af« mm 
grounds in the opinion of this observer for the theory ti 
these smaller cells i*epresent the cerebellar elements of 
ganglion (Pig. 31) while the large cells ai'e connected will 
the mutiir nerves of the projection tract. 

Meynert has recognised this collection of nerve ceJ 
which presents, to his mind, most strikiug peculianties. Ik 
locates it in the inferior regions of the caudate nuelens^ ex- 
tending from a point just above the lamina perforata, la* 
tenor to the neighljorhood of the so-called afiterior &>m^ 
mlssure. The peculiar anatomical features of this mass an? 
stated by this author to consist (1) of an agglomeration ti( 
small nerve cells into i^iles, which are distinctly circom- 
scribed ; and (2) of very small gmnules ii\ fi in diameter) 
packed into close masses, and distinctly isolated. This laltei 
element is not found elsewhere in the collective cerebral 
ganglia, and is believed by Meynert to indicate a structiuil 
relationship between the caudate nucleus and the olfaotoiy 
lobe. 

We find other cells in the corpus striatum in addition 
the two varieties of nerve elements already described, 
of the neuroglia; but they are of little if any importani^ 
(as far as we at present kuow) from a phj^siological or clinical 
point of view. 

The NERVE FIBERS ASSOriATED WFTH THE CORPUS 8' 

ATUM may be divided into two ^oups, afferent and efferent*^ 

The afferent set comprise (a) those which spring frf>in 
cortex and enter the substance of the ganglion ; and (A) soi 



ioD^I 




CA UD0-8TRIA TE FIBERS. 127 

fibers probably connected with the superior peduncles of the 
cerebellum, which are capable of being traced to it. 

The afferent fibers of the caudate nucleus may be traced as 
five distinct groups, as follows : 

1. Fibers which spring from the entire length of the arch 
of the cerebral hemisphere (corona radiata). 

2. A bundle of fibers springing from the cortex of the tem- 
poral lobe to the most anterior part of the caudate nucleus, 
following a curved course along the inner border of that 
ganglion {stria cornea). 

3. Fibers which arise from the cortex of the olfactory lobe 
and pass to the corpus striatum. 

4. Fibers which unite the cortical substance of the sep- 
tum lucidum with the inferior region of the corpus striatum 
{peduncvZus septi lucidi). 

6. Fibers of the cerebellum, which reach the cerebrum as 
described above. 

The upper border of the caudate nucleus of the corpus 
striatum which is at the same time its ovter^ seems to be the. 
pole toward which the afferent fibers of the ganglion center, 
with the exception of the stria cornea. The lower or inner 
border acts as the peripheric pole, from which its efferent 
fibers emerge. 

The efferent set comprise those fasciculi which help to 
form the cerebral peduncle (crus cerebri), and which are dis- 
persed, after having passed through the i)ons Varolii, chiefly 
in the different segments of the spinal cord.' 

Let us now consider certain points in the arrangement and 
probable function of these groups of fibers. 

The afferent fibers which spring from the cortex and unite 
with the nerve cells of the corpus striatum may be designated 
as the '* cortico-striate " group. They appear to spring chiefly 
from the psychic {X) and motor regions of the cortex ; hence 
we are apparently warranted in attributing to the corpus 
striatum some special association with these two functions. 
This view is, moreover, sustained by the fact that the efferent 

I of tlie •fferent flbera of the corpuB ■tiiatam probably go to the cerebellum. 



fibers of this ganglion are lodged principally in the mcdm 
pathsi of the pn>jection system.' 

The experiments of Pritsch and Hitzig have demon^tratd 
that weak gidvanic currents (when applied to certain regions 
of the cortex apparently connected with the corpus striattim 
by radiating libers) pinidiice muscular movements in Bpeasi 
regions of the body ; and they were thus enabled to create 
at will motions of the eye, tongue, mouth, neck, and linib^. 
ftirtholow has demonstrated the same physiological result b 
the brain of a man, in whom the top of the sknll had ^ 
dedtroyed by disease. Both Bourdon and Luys have ui>ruv 
ered an atrophy of cortical motor centers (as the result of Kiss 
of its function) in subjects deprived of a limb by amputation. 
In spile of these farts, however, we are still unable to state 
jR>sitively that all tlie fibers which radiate from the motor 
©enters of the cortex ai^ directly united with the nen^e c**Us 
found in the corpus striatum, since the so-called ^* internal 
capsule "'seems to pass directly through the ganglion with* 
out meeting any interrupting cell elements in its pa^mgf. 
Whether this is actually the case or only an apparent one, 
It is tmposisible to detennine from our present knowledge 
The latest Investigations of Flechsig seem to show that the 
mvc^dUnl ** pyramidal tmcts-'are independent of any strnct' 
nnil rf^lallon^hip with the cells of the basal ganglia. 

Among tlie afferent fibers of the corpus striatum, I have 

HieullomMi certain fibers which are apparently terminal exj^ui- 

%{k\^%h of the .^Hptrhr prduneles of the cerebellum. It seems 

— • t n M t T'pted by most observers that the fibers of these 

I decussate in the median line, and afterward 



.v. .1 i 



^*\'0S. A»i »»*• "•' 




.*»,iH!»t Into flfrnrnil ubc among neuroloqjista by Meyncit. (Seep^gviL) 

111 cnpsttle " ftepRruk'8 Uio two part$ of the corpus nriMlitm hi 

,. M..1- iti«v«li>u» frani the optic thalamus posteriorly (Fig. 1ft). Ii *s- 

4« • )«rl of the ttcvtmd projection ayfiteoif constitutinir certain tnoitflr 

fiMiul ntlhln lhi***Aa«* crujtt cerebri ^^ and the " trffmenium erwru 

llw K*ft»K <ho«ko fiWr# which arc connectmi with the tail of the Intnk 

1- ftrbluin are described bj 31e7nt*rt a« pur^itDg a 

' iti to appe<ir to emerge from among the external 

ivwii fftiieiciiU of the crua. To raaeli tUs prtrtlna 
^,, i:;. iwiennediaie tmndlea. 



FUN0TI0N8 OF CORPUS STRIATUM. 129 

become associated in the formation of two masses in the eras 
of a reddish color (red nuclei of Stilling). From these may 
be traced numerous filaments of a yellowish color, that, after 
extensive interlacement with each other, are believed by Luys 
to be prolonged to the yellow nucleus of the corpus striatum. 
An attractive theory has been advanced by Luys, that these 
delicate fibrils are the wires which carry the continuous cur- 
rents of electric force, which overflow from the cerebellum to 
the corpus striatum, and thus constantly charge the cells of 
that body, which are liable to become exhausted by the con- 
trolling influence exerted by them over motor impulses trans- 
mitted from the cortex of the cerebrum. Physiological ex- 
I)eriment points strongly to cerebellar innervation of motor 
acts. Disturbances in coordination of movement are pro- 
duced by disease of the cerebellum, and motor acts appear 
to be weakened. These phenomena are of the greatest im- 
I)ortance, as they tend to confirm the view taken by Luys 
regarding the foci of motor innervation. 

The corpus striatum, like the optic thalamus, may be con- 
sidered, therefore, '* a* a territory in which cerebral^ cerehelr 
lar^ and spinal activities are brought into intimate commu- 
nication^^ To quote the opinion of Luys, " it acts as a halting 
place for voluntary motor impulses emitted from the cerebral 
cortex. It enables these impulses to become modified and 
possibly reinforced by currents derived from the cerebellum ; 
and, by its efferent fibers, it transmits centrifugal motor im- 
.pulses along the projection system to different groups of cells 
within the spinal gray matter, whose individual functions 
they tend to evoke." 

This ganglion probably acts as "a condenser and modi- 
fier of all motor acts which are the result of volition, and 
manifests, through the agency of its satellites (the cells of 
the anterior horns of the gray matter of the spinal cord), 
the outward expressions of our personality." Without the 
influence of the cerebral hemispheres, it is also capable, by 
means of cerebellar innervation, of governing all the complex 
mnscalar movements required in maintaining equilibrium (co- 



FUNCTIONS OF CORPUS STRIATUM. 131 

Experiments made upon the caudate and lenticular nuclei 
can hardly be said to have afforded results which can be made 
the basis for i)ositive deductions respecting the functions of 
each. Nothnagel employed injections of chromic acid into 
the substance of each, and also destroyed them by means of 
an instrument devised for that purpose, but he made no i)osi- 
tive conclusions save that the lenticular nucleus seemed to 
have a more decided influence upon motion than the caudate 
nucleus, when both sides were simultaneously destroyed. 

Some observers claim to have removed the entire ganglion 
without any marked disturbance of sensory or motor phe- 
nomena. Some observations in comparative anatomy show a 
relationship between the caudate nucleus and the motor fibers 
of the leg, and a similar relationship between the lenticular 
nucleus and the fibers destined for the arm. 

In no instance, to my knowledge, has the destruction of 
either of its two nuclei produced psychic effects. When aki- 
nesia (loss of movement) has been thus artificially produced, 
it seems to be absolutely confined to the opposite side of the 
body. In cases of extreme rarity, lesions have been shown 
clinically to have resulted in a paralysis of motion of the same 
side ; but Plechsig has helped us to properly interpret these 
cases, as they afford evidence of an individtud peculiarity in 
the rdative number of decussating and direct pyramidal 
fibers. Perrier has produced convulsive movements of the 
opposite side of the body by faradism of the corpus striatum, 
and Carville and Dnret's observations seem to be in full ac- 
cord, thus sustaining the theoretical view first advanced by 
Carpenter and Todd, as to an exclusively motor function in 
this ganglion. Burdon-Sanderson also has produced localized 
movements by electric stimulation of the white matter of the 
brain in the region of the corpus striatum. Danilewsky has 
observed that modifications of the circulation and respiration 
were produced by irritation of the lenticular nucleus ; and 
also, to a slight extent, when the gray matter of the hemi- 
sphere overlying this nucleus was irritated. It is extremely 
doubtful, however, if these effects are due in reality to local- 



132 



THE BHAJX 



ized irritation, because the fibers of the cerebral pedaticle 
in close proximity. The removal of the hemisphews al 
the basal ganglia does not seem to effect eitlier the respi 
or the circulation. 

It would be rash to draw any conclusions of a posjfi' 
nature in the face of such a conflicting mass of exijerimeoi 
and clinical evidence. It can not be disputed, however, tbit 
those who support the doctrine that the fibers of the inlemal 
capsule are the direct paths for motor and sensory impulses 
and that all effects of experiment upon or disease of th 
corpus striatum are the result of pressure exerted upon tkii 
tracts have^ in the light of our present knowledge, the most 
plausible theory. In what way this path of cond action is 
brought in direct or indirect de|jendence upon the cell ele- 
ments of the nodal masses, with which it bears so intimate 
relation, it is impossible to state positively ; bur it can not 
denied that it seems to have the power of isolated condiictioii,^ 
in spite of any connections with ganglion cells, which may 
yet be proved to exist. 






THE OPTIC THALAMUS, 

The fibers of the *' tegmentum cruris " (Figs* 6 and 8) . 
connected chiefly with the following ganglia : the ''optic //mfe- 
;/*?^"*/ the '^ corpus quadrigeminuni^'' ; the red nuclei 
Stilling; the ""^ corpus mamillare^^; the ^^ pineal glaiid'^ 
narium) ; and a ganglion embedded in the pons VaraliL The 
two ganglia first named have a connection with the optic tincC^ J 
in addition to a connection with the spinal cord. For this] 
reason, the ^^ corpora gerdculata-^ may be considered as 
appendage to them. 

Let us consider, before the other ganglia are touclic 
ui>on, the peculiarities in arrangement of the optic tbatamoflr' 
and its probable functions.' 

* The term ** thalmmffphafon '' Is »oiDctiroe« itppU«d to the thaUniM, plmtA 
and pituilitfy body when colleciirdy oansidercd. Thc«e niftj be considered •» 
logically rcliitcd to each other. 

* The gaDgUft of origiD of ttie icgioeiiUl fibcn are tcparitoly oooj^idored on a 

qutmi p«^ 






I 

i 



THE OPTIC THALAMUS, - 133 

This ganglion appears, at first glance, to present its gray 
matter, exposed and uncovered, as a lining to the third ven- 
tricle. In this region, a band of white fibers, the '^stratum 
zonale^^^ defines its limits and separates it from the tail-like 
projection of the corpus striatum. 

When the gray lining of the ventricle is examined, how- 
ever, it becomes evident that it is structurally independent of 
the cells of the optic thalamus, because it can be traced as a 
direct continuation of the central tubular gray matter. It is 
in reality foreign to the thalamus, although it is probably con- 
nected with nerve fibers which penetrate its substance in 
order to reach certain nuclei of the central gray matter. It 
will be described in detail later. 

The optic thalamus, as well as the corpus quadrigeminum, 
is poorly developed in the human brain, when compared with 
that of the lower animals. In shai)e, it has been compared 
by Meynert to "an arch surrounding a transverse axis"; in 
which respect it bears an analogy to the caudate nucleus of 
the corpus striatum, and the general arrangement of the cere- 
bral hemispheres. The axes, around which the thalamus ap- 
X)ear8 to arch, comprise, according to Meynert, the brachia of 
the corpus quadrigeminum and the corpus geniculatum inter- 
num. The greatest breadth of the thalamus lies posterior to 
the axis. The greatest thickness is found just in front of the 
axis. At its anterior extremity, the breadth and thickness 
attain their minimum. 

When the fornix and velum interpositum have been re- 
moved and the optic thalami are viewed from above, they 
api)ear as oval-shaped masses of gray substance covered 
superficially by a thin layer of white fibers. A longitude 
nal groove (Fig. 33) may be detected on the superior surface 
of each, which inclines slightly inward so that its anterior 
extremity approaches the mesial plane. It terminates before 
the anterior extremity of the thalamus is reached. This 
groove is caused by the thickened margin of the fornix, which 
extends over the surface of the thalamus along the line of the 
groove. The anterior part of the thalamus is raised into a 




Fio. O. — VU« /¥^m abow t/ ih€ third vmtride and a p^rt t>/ ike ial^rai t^ 

(Hcnle.) 

Tilt brtin hn& been uliccd borizootatJv, immodiatcl^* below the corpus ainoAittn, uid (W 
fornix ftitd velum ioterpo^Uuni 1i«Tf* biH;n removed. TTio^ ttniturtuif op|(c>«» ; fk, iU 
Anterior tubercle; Pv^ piHvinar; (^am, middle nomminsure strctchiog between tfe 
two optic thulaiiii acrofiis the middh? of the ibii " ' ; Cf\ columui of lUe fofw 

nil; CVi, pineal glaod projoctinfj downward an i betwocn the (■uftcrior i 

pora quadn^cmina ; iS/, stria terminftli<»; C«, hHntu- iuiidatusof tlie cariiQii atrk* 
turn; r*/, ventricle of the *>eptura lucidiim ; OA, section of the penu of ib^ < 
catloiSiUD; Pen^ coramencenient of the pin» al stri.i or [peduncle, Tfo ; Ca/t, pottt 
oommissuro. 

prominence, the so-called ^^miterwr tubercle,^^ wMcU prtijc 
into the lateral ventricle and is covered with the epitheH 
lining of that cavity. It lies above a part of the lenticuh 
nuclena, as may be seen in all cross-sections of the cerebmni^^ 

* Th« anteriar tub«rcl« U far tber retnoTed from the lerel of tli^ btae of the { 
than any olber part of Ibc thahuntis. 



THE OPTIC THALAMUS. 135 

At the x)osterior and inner part of the thalamus, \b seen, 
as in front, a posterior prominence or tubercle, the ^'pvlvi- 
nar.^ This projects over and partly conceals the brachia of 
the corpus quadrigeminum. 

Below and external to the pulvinar, another well-marked 
eminence, the ^^ovier genicvZate hody^^'^ may be seen, which 
lies external to and above the ^^ inner geniculate body^ 
These two eminences * are separated by one of the roots of the 
optic tract (the upper brdchium). The optic tract arises from 
this brachium and the two geniculate bodies, and curves 
downward and forward around the crus cerebri. 

Such being the general direction and shape of the thala- 
mus, we are prepared to consider the arrangement of the 
fibers which are connected with it. It presents, in the first 
place, three blunt pedicles, which become united with some of 
the fibers of the sui)erior projection system {corona radiata). 
Those fibers, which become ultimately united with these blunt 
processes, may be traced to the cortex of the frontal lobe, of 
the walls of the Sylvian fossa, and of the temporo-sphenoidal 
lobe. The ganglion is also in intimate relation with fibers 
which radiate to the cortex of the occipital and parietal 
lobes. 

The external and inferior surfaces of the thalamus are 
not free, but are united by means of nerve fibers with other 
parts of the brain. The external surface lies in close relation 
with certain fibers of the "crusta,'' and " tegmentum cruris," 
which pass between the lenticular nucleus and the thalamus 
— those forming the * 'internal capsule" of the cerebrum (Pig. 
84). The inferior surface is in relation with the crus ; and, 
more anteriorly, the corpus albicans and the tuber cinereum 
lie below it. 

The outlines of the surfaces of the thalamus and the 
lenticular nucleus of the corpus striatum, as seen in all verti- 
cal crofls-sections of the cerebrum, may be roughly compared 
to the form of a square whose two halves are defined by a 

> Tbcw bodies are diicuiied more in detidi in a subsequent page, as ganglia of origin 
of tflgneiital llben. 



THE BRAlK 



cliagnonal band, the ** internal capsule^^^ running from tlj 
upper and outer coi-ner to the lower and inner corner, 
halves correspond to the respective ganglia. It 



.— '^-f.f.^ 



FlO> 34. — Section f*tro9a the opt k thcdatmt^s d^u . ..^-;.,. hiatum in thf rt^tm oftS^ miM 
commiiturf, (Schiiferf after tt pre{>Anition l>y Mr S. G. Slmttuck.) Katuiml tiM. 

t/t^ thalnmuB; a, c, t , ita anterior, ext<?rua1, and intenial iiudd jt^^^ -*■- ^ j^, j^^ 

licL'tl lajtr; w, t., nmldle commisiiure; above and below H b ' ftc lirri 

ventricle; <r, <?., cor-jma ealludum ; /*, fornix, aepamted from fh ckao^ 

(lialatnus hy the veluu] intcrpositum. In the middle of tbU arc ^ -o wm^ 

of GalcQ ttnd the choroid ptcxuttes of the third ventricle; and nt it^ > _ duiW 

plexui^ej of the lateral ventricleii; /. ^,, tienia !«emldren1aru ; **r.^ forwatxi pfalooci 
tion of tlie cruj*ta panging latcmlly into the intcmnl capsule, i. e. : #. t, r., snhtliataiir 
pmlongrttion of the tcgtci-ntum, consistinj! of (1) the dorf^al Jayer, <2) the lOOt Ift- 
ceiia^ nnd (^) the corpus subthaiaiDicum ; h, n., sub^^tanliu uigm ; r», c, ntictciin 
tus of the corpus striatum \ n. /., nncleus lenticnlaris ; e, c, external cupduJe ; r/, 
trum ; /, lidaod of Ueil. 

worthy of remark, in this connection, that the surface of 
thalamus which lies in contact with the internal capsule 
the cerebrum marks the central or receiving pole for the flbe^ 
which join it w ith the cortex of the cerebral lobes. This b 
not the case with the lenticular nucleus, as has been stated att^ 
a previous page/ 

The external surface of the thalamus (which lies in confaft" 
with the internal capsule of the cerebrum) presents a pecull 
appearance, which has given it the name of ^'lattice layei 
(Kolliker). AU along this surface, radiating fibers pass o^j 
of the thalamus to become intermingled with the libers of ll 
internal capsule, and to be subsequently distributed to tl 
cerebral cortex. Those from the front of the ganglion 

* See pages which treat of the COepx^s Stkiatuil 



8UBFACES OF THE THALAMUS. 

the frontal lobe ; those from the middle are distributed to 
le posterior part of the frontal and to the parietal and tem- 
jro-sphenuidal lobes ; those from the posterior part can be 



n\ 



u 



tS. — Ri^kt ha\f 0/ tJ*0 tntephjdi^ peiunde and eertbdlum om ncen from the ifuidt 
0/ a tnttiiati »tx(ioH, (Allcii Thumsou, after Ilriilicri/) 

, fight optic ti^rvc; bobiiwl it the optic commifsuiv ahided t lU, ri^ht thin! n^rre; VI, 
nt ' V\ third vcntrk'Us 'jT^'Jjat^^i I'^"*"f f^'t'''' -tionof 

t! biwly; p^ pme»1 tl*w*J; l>cl«>w iIj* hIbIW It* ( ire; <xi, 

ttr ...,-..,... J.;, <.., J ..,,1 (n^hind it tlie tliv-i "1 .... fomii; 

/. M (I'livitv): /<*, t'l' iltheoorpns 

all pillQT of thef«MJ ^ < wall of ihe 

thini vrntriclc; em, rniiinu>.Huni rooDi?- ; */>, ^iria pint'nii&^ or peduncle of pinral 
^Uml; (/f tainitta iittadrigi^iinna; <im, liqiii^duct of Sylvitie near the* fnurltt reDtiido; 
*r, emu cprthH ; fV, jh»d»* vnnAVi ; Af^ me<Ju1la ob]oni;at« ; behind lhe«e the ccri'lnji. 
him ; I to 2, lamintt of the a^tfrro-^jtcrior lobe ; between P and 1 ire Pei*ii th<J 
** uia «fid ttntrttl toU In section; H, puMterio inferior lobe; 4, lotmlua ^radius ; 0, 
' lobe ; 6| amif^aloid lobe. ' 

timced to the temix)ro-8phenoidal and occipital lubes. From 
the n!fdon of the [julvinar, or posterior tubercle, fibers can be 
iced into the npHc tract, and to Mnnk's visual area of the 
of the occipital lobes (Wernicke)/ 

* WifnleWi tmet of 6ber» past beneath the *r»ffut*r f^mn (In which Feirier pl»cCT 
' ceotcfi of tblon) but terfiilii4te« In the eortex of the occlplml lobe, Tl»e»e fibem are 
i la a ittbiec|ii«nl cut Itliifttnitlre at the opUo flben. 





^138 



THE BRAIK 



The lower surface of the thalamus is eonlinQons, 
orly, with fibers* of the tagmentum cruris (the sub- 
tegmental region) \ in front, however, this proloQgaliQ& i 
fibers inclines to the outar ride of the ganglion and 
lost in a layer of gray matter seen in the floor of the ventiickv_| 
which enn*esponds to the ''*' anterior perforated lamina^ \ 
the base of the l>rain. 

The lower surface of the thalamus is itself prokmged, i 
teriorly, into a tract of libel's which run downw^arfl and out-' 
ward into the white substance of the cerebral heniisphcft 
forming the so-called '^ lower peduncle of the tfialamnjt.^* A 
bundle of fibers, the ''ansa lenticukiru,''^ passes undenieetk 
the thalamus and above the lower peduncle of that ganglid 
from the mesial part of the crusta to the lenticular nQckfi& 
Between these two tracts of fibers gray matter is iDlerjKi^^; 
the thi*ee» co]l«*ctively considered, being called the *^suh^tanik 
innomifiafa of Heiiy 

The substance of the thalamus consists of nerve fibers and 
nen e cells, variously disposed ; but the exact arranj^emenr 4 
each, and the connections of the nerve cells with sj>ec!ial fillers, 
is a subject for much future investigation. Many of ih? 
theories advanced will be discussed later. 

The thalnmi approach each other very closely in the 
median line ; and, slightly f<irsYard of the middle of the thini 
ventricle, are joined by a band of gray matter, the 80-<mUi*d 
^*7niddle^^ or ^^soft commUmire^^ of the thalamus (Fig. M\ 
This is sometimes doul»le, and occasionally is absent. It \s 
often torn across in removing the brain. This connecting 
band is composed of gray matter. 

Not more than one half of the actual antero-posterior meaa- 
urement of the thalamus is exposed in the third ventricle. 
It must be noted that the anterior tubercle appears in the 
lateral ventricle ; and that the luihinar, or posterior tul)ercle, 
lies in a plane posterior to that which would intersect the 
corpora quadrigemina. Note also that the anterior cotmnts* 

* Meyuert ctftimA that tbcsc fibers wAb^ from tbc cortex of the fo6M of Sylvlut mad 

the temporo^phcnoidikt lobo. 



1^^ 



J 



FIBERS OF THE OPTIC THALAMUS. 139 

sure of the third ventricle does not connect the optic thalami, 
or apparently have any structural relation with them. The 
posterior commissure is probably a continuation of the com- 
missural fibers of the fillet {lemniscus)^ which pass through 
the substance of the optic thalami and diverge in the cerebral 
hemispheres. These fibers may, in part, act as commissural 
fibers between the thalami. They are also structuraUy related 
to the pineal gland. 

The NERVE FIBERS, which may be enumerated as inti- 
mately associated with the structures of the thalamus, can be 
divided into sets, as follows : ' 

1. Fibers of the superior projection system (p. 31), which 
serve to unite the thalamus with the cortex of the frontal, 
parietal, occipital, and temporo-sphenoidal lobes, and the fossa 
of Sylvius. 

2. Certain fibers which can be traced directly into the optic 
IrcLctj thus proving some functional relationship between the 
thalamus and the retina. 

' The system of nenrc fibers that exists in connection with the thalamus, according to 
the late researches made bj Flechsig, may be thus summarized : 

1. By means of tlic so-called '* corona radiata," the thalamus is connected with all 
part^ of the cerebral cortex. 

2. Fibers from the frontal lobes appear to be associated with both the anterior and 
outer nuclei and the stratum zonale of the thalamus. They reach that ganglion by means 
of the anterior part of the internal capsule. 

8. The cortex of the parietal lobe are associated with the outer and inner nuclei of the 
thalamoa and the stratum sonale. 

4. The cortex of the ocdpiul lobe is associated with the pulvinar and the stratum 



6. The cortex of the Sylrian region is Joined to the outer and inner nuclei of the 
thalamus and the stratum zonale. 

6. The cortex of the hippocampal region is connected with the outer nucleus of the 
thalamus by means of the fornix, after its fibers have first passed through the substance 
of the corpus mammlUare and turned upon themselves. 

7. The bundle of Vioq. d*Azyr*s pends fibers to the fornix and also some to the reticu- 
lar formation of the medulla, passing between the red nucleus of the tegracDtum and 
the substantia nigra. 

6. The so-called "Meynert's bundle** is composed of fibers that spring from the 
stratum zonale, the gray lining of the third ventricle, and the ganglion of the habenule. 
They are connected with the ganp^lion interpedunculare, but can not be definitely traced 
lato the reticular formation of the medulla. 

9. Fibers from the medullary lamina of the tlialamuH pass downward to the red 
andeos and the gray matter adjacent to it. They probably extend to the cerebellum, 
hat Jhsj oaa not be traced beyond the red nucleus of the tegmentum. 



THE BRAJN. 



I 



3. Fibers of the tegmentum cruris (Figs, 6 and 8), wliifk 
connect the thalamus with the sensory tract of the spinal oofi I 
As stated in a previous page, these are to be classed as i 
of the middle projection system (Meynert), 

At the upper level of the middle point of the thabmtiv^ 
the sensory libers of the tegmentum leave the internal caj 
to radiate toward the cortex. This has been termed the ** 
feur sensitif " by the French authors. Here the 
fibers that escape from the thalamus become intermingled witi 
the sensory capsular fibers. Flechsig claims to hare 
able to trace the sensory tract to the cortex in thf^ embryo^' 
since they become medullated at a later period than do tk 
radiating fibers of the thalamus. According to this obsprrcr 
they end in the cortex of the parietal lobe, behind the ptJit- 
central gyrus. 

4. It is claimed by Lays that the anterior tubercle of the 
thalamus c^n be proved to be directly connected with spedal 
fibers which lead to regions of the cortex functionally related 
with the olfactory sense, 

5. There is strong clinical evidence to be addnced in sui 
port of the view that the sense qf hearing is, in some imper 
fectly understood way, connected with the thalamus. 

FUNCTIONS OP THE OPTIC THALAMUa 

Efforts have been made by some of the later anatomii)t5|J 
who have specially investigated the structure of the brain, 
subdivide the gray matter of the thalamus into circumscril 
masses or nuclei, and to trace the libers which appear to arisi^ 
from these nuclei to special regions of the bmin and spii 
cord. Among the most attractive of these attempts may 
mentioned that of Lays, whose views will be subsequently! 
given in detaiL Whether clinical research and physiological] 
experiment will confirm all of these attractive theories ai 
place them upon a ground as worthy of credence as the d€ 
ductions of Broca and Ferrier regarding the functional attri- 
butes of other parts of the brain, time alone can decide. 

The deductions which have been drawn from pathology UM 




FUNCTIONS OF THE OPTIC THALAMUS. 141 

well as from the results of physiological experiments, made 
with a view to determine the functions of the thalamus, are 
apparently contradictory and more or less uncertain. Paraly- 
sis of motion has been observed to follow the development of 
a lesion confined to the thalamus, and also to co-exist with 
lesions which have involved the corpus striatum and the thala- 
mus conjointly. The question at issue is, however, whether 
the thalamus can be shown to exert any positive influence 
over sensory impulses, and whether lesions of that ganglion 
cause impairment or loss of sensation. Vulpian observed only 
impairment of motility from lesions of the thalamus ; Luys 
has collected cases which apparently sustain the view ad- 
vanced by him, viz., that a center which presides over gen- 
eral sensation is located within the thalamus ; and Crichton- 
Browne has also collected cases where a diminution or aboli- 
tion of sensation has been observed to co-exist with lesions of 
the thalamus of the opposite hemisphere. 

Ferrier reports an experiment made upon a monkey which 
seems to sustain the view of Luys and Browne. In his first 
operation, the expanding stilette (which was pushed into the 
brain with the intention of reaching the thalamus) was not 
inserted far enough, and no marked sensory phenomena fol- 
lowed ; but, when the instrument was subsequently introduced 
through the same tract far enough to reach the thalamus, 
tactile sensation was thoroughly destroyed. In reference to 
this exi)eriment, Ferrier speaks as follows : 

** Without for the present attempting to estimate how 
much was here due to the lesion of the optic thalamus as 
such, and how much to the medullary lesion external to it, 
w© have in this experiment a conclusive proof of the abolition 
of cutaneous sensation by an injury in and around the optic 
thalamus. '^ 

Veyssidre has showTi by experiments made upon dc»gs that 

section of the internal capsule in the region of the thalamus 

causes hemian^DSthesia of the opposite side of the body. 

Nature has, moreover, verified these experiments in man, 

since Torek, Charcot, and others have clinically observed the 
19 



THE BEAIX 

same effects, as the result of disease of corresponding 
Unfortunately for science, the optic thalamus is situated rF 
point where the motor and sensory tracts have nut as yet b^ 
come very clearly diflFerentiated from each other. Here tki 
two appear to be more or less intermingled. 

We have reason to believe that the cerebral cortex 
brought into relation with all the oi'gana of sense by roe 
of fibers which pass either through the thalamus or the 
terior fibers of the iiitenial capsule of the cerebrum which Bf' 
adjacent to its external surface. With the excei^tion of tl 
sense of smell, there is no other medium for the transmit 
of such impulses to the hemispheres. 

The coui*se of special nerves and the value of morbid, 
phenomena of the special senses will be discussed later 
connection with the internal capsule, the corpora qua 
gemina, and the medulla. 

According to the researches of Luys, /our isolated 
glions may be demonstrated in the thalamus, Arnold, 
common with some other anatomists, has recognized threes 
these, and the fourth is now adde<l by tlie author quote 
This author states that these ganglia am arranged in an ai 
tero-pos terior plane, and form successive tuberosities ni 
the thalamus, giving that body the appearance of a conj 
erate gland (Fig. 33. ) The fulkjwing paragraphs exrur* 
views relative to these tuberosities : 

The anterior ganglion (corpus album suhrotnndum) 
especially prominent. It appears to be developed in animal 
in proportion to the aciUene^s of the sense of ^'i/nell/ Bj 
means of the *' tfcnia semicircularis," this ganglion (aecoi 
to Lays) may be shown, in the human species, to be connected 
with the roots of the olfactory nerve. Respecting it he saydj 



* The Iftlc n*9CArchca of FIccUsip mid hUo those of Gnddcn (the fonucr of whom ] 
studied the relative periods of dcveiopmcnt of tht* main nerve Iracta of the hm!n« i 
the Uucr \\a$ studied the de^nemtivc clmniro« that follow the desiirnetion of th«* i 
liuporuuit tracts in tirwlj-hom nuimaU) (ail to <!liow any difw*t ft»sociiitioTi of th 
oUftctorr ncnre flberf with the tlmlamuii, as a supfmri li» lliu thun'cthral view of L«| 
ba^ed upon cliniecil data. We arc ihcfoforc forot.'d u> b<dievti ttiat the aniNKJaUOfi It i 
indirect one, if any ciisXB, 



LUYS'S THALAMIC CENTERS. 143 

"Direct anatomical examination shows that there are inti- 
mate connections between the anterior center and the periph- 
eral olfactory apparatus. On the other hand, in confirma- 
tion of this, in the animal species, in which the olfactory- 
apparatus is very much developed, this ganglion itself is pro- 
portionally well marked. Analogy has thus led us to con- 
clude that this ganglion is in direct connection with the 
olfactory impressions, and that this marks it as the point of 
concentration toward which they converge before being radi- 
ated toward the cortical periphery." 

The second or middle center is in apparent continuity with 
^e fibers of the optic tract. It may therefore be considered, 
on the same grounds as those previously quoted respecting 
the anterior center, as a seat of condensation and radiation of 
visual impressions.* There seemed to be undisputable grounds 
for the belief that the external geniculate bodies^ the superior 
corpora quadrigemina^ and the pvlmnar^ are, in some way, 
also associated with the perceptions afforded by the retina. 
Moreover, the convolutions of the occipital lobes may be 
added to the collections of gray matter previously mentioned, 
since physiological experiment tends toward that view. 

Ritti has pointed out that irritation of the thalamus may 
play an important part in the development of hallucinations. 

We know that extirpation of the eye is followed by more 
or less complete atrophy of the outer geniculate body of the 
opposite side, although the inner geniculate body seems to 
remain unaffected. The experiments of Longet, who de- 
stroyed the optic thalami upon both sides without being able 
to note any impairment of vision or influence upon the move- 
ments of the pupil ; and those of Lussana and Lemoigne, 
who found that -blindness of the opposite eye followed uni- 
lateral destruction of the thalamus, may suggest the possi- 
bility, in the experiments of the former, of the escai)e of this 
center and, in those of the latter, its destruction. It is diffi- 
cult to devise any experiment which will positively settle the 

' Luys states that it is scarcely visible in those animals (the mole as an example) 
the optic nenres are rudimentary. 



^u 



TUB BRAIN. 



hearings of the thaJainus upon rision ; hecause it is vlmcd 
impossible to destKjy special portions with accuracy, cir, 
this were insured, to avoid injury to adjacent stractur 
Foumie claims to have effected the separate atmiUUatiocicir 
the special senses of smeU and vision by injections made ti; 
different parts of the thalamus of animals ; and bis expeiP 
ments, if subsequently verified, will tend to confii-m some of 
the theories advanced by Lays. 



ji 



-jti 



Fio, 36,— wi diatom of the nuclei 0/ tfte optic thdfmmit and the convcr^tH^ ji^ent 
aoeiaied wUh tnctn. (Lti^r;^.) 

1, coTirorging fibers of posterior convolutions; 2, Pttnio» af middle c * 
of Anterior convolutions ; 4, 4\ 4 ', cortical periphery us rolat* 
mnsi^es; S^ optic tlmlamus; 0, corpus titriatum ; 7| ftOtf"'" 
middle (optic) center; 9^ median (tttfuniii^r) center; 10, 1 
11, eenlral ^niy region ; 12, jt**wndin«; prny fihers of vij*t , 
optic fibers; 14, iL^oendin^ sennitive libers; 15, a.H^endin^ aef>uMic li 
of untero-ktcrnl fibers of the spinal axis going to be lotft in the cor| > 

The third center ('' median ganglion " of Lnys) is desc_ 
'%8 about the size of a pea, and situated mathematically in 
exact* center of the thalamns. To it the discoverer ascribes 
the function of presiding over and condensing all eensi 
impressions, 

The/ourlh or posterior center is stated to act as a haltin, 




wmm 



iJk. 




LESIONS OF OPTIC THALAMUS. 145 

place and condenser of auditory impressions. Two instances 
where the brains of deaf-mutes were found to present a local- 
ized lesion of this center are reported by Luys. 

The views here expressed are quoted on account of their 
originality ; and because the author of them ranks high as an 
authority upon the subject of which he speaks. 

The numerous cases of cerebral haemorrhage which have 
been reported, where the thalamus was apparently the seat of 
localized injury, are too often accomi)anied with a clinical 
history which points toward pressure upon the internal cap- 
stUe to be of value as confirmatory evidence of the existence 
of special centers in the thalamus. . The effort of Luys to 
adduce cases of hemianesthesia in support of his views re- 
garding the function of the ^^ median center" of the thalamus, 
merely because a lesion of that ganglion was found in an area 
defined by him as the normal limits of that special center, 
must not be deemed conclusive; because the same effect 
might have been produced by pressure upon the posterior 
third of the internal capsule of the cerebrum. There is every 
reason to hope and possibly to believe that sooner or later 
isolated ganglia within the optic thalamus w^ill be demon- 
strated to exist by normal and pathological anatomy as well 
as by physiological experiment ; but the conclusions even of 
so prominent an author should not be fully accepted without 
further testimony to substantiate their accuracy. The 
anatomical researches of Meynert do not agree with the con- 
clusions of Luys. 

Some interesting cases have, however, already been 
brought forward, which certainly seem to sustain the views 
advanced by Luys. A case rei)orted by Hunter,* where a 
young woman successively lost the senses of smell, sight, sen- 
sation, and hearing, and who gradually sank, remaining a 
stranger to all external impressions, disclosed at the autopsy 
a fongns h»matodes which had gradually destroyed the optic 
thalamus of each side, and the optic thalami alone, if the 
drawing given is reliable. Again, Foumi6's experiments on 

> *« MediocMOiirg. Traiu.," London, 1825, vol. xiiL 



14« 



THE BRAlNi 



living animals pciint strongly to the existence of locaQiri 
centers in the thalamus. Three instances uf unilareml d**- 
struct ion ot smell, obseiTed by VoLsin and reported by LofSw 
have been found to be associated with a destructifm <if lb? 
anterior center of the thalamus. An hemorrhagic effusion into 
the thalamus, on a level with the soft commissitre (the sit» 
don of the optic center of Luys), produced (in the exp**mf»c^ 
of Serres) a sudden loss of Bight in both eyes* Ritti's paji^ 
upon the effects of irritation of the thalamus upjon the rf^W 
opment of haUueinations^ lends strength to the vii»w thai 
tliat ganglion in some way I'egulates the transmission of set 
sory impressions of all kinds to the cerebral nurtex ; and ci»ih 
finns the ofjinion that *' the optic thalami are to be regEid^i 
as intermediary regions which are interposed between the 
purely reflex phenomena of the spinal cord and tlie aetiritk» 
of psychical life." 

The view taken by Lussana and Lemoigne, that the optic 
thalami contained motor centers in animals for the lafenil 
movements of the fore-limbs of the apposite side, seems la tx 
completely overthrown by pathological statistics in the hunm 
race. The results obtained by these experimenters are al^^ 
at variance with the belief, which has now become genenl 
among neurologists, that the thalami are intimately connected 
with the sensory tracts of the cerelirum and cord ; since they 
concluded that no evidence of i>ain or any loss of sensibility 
resulted from injury to these bodies. 

The effects of all experiments on animals, however, agK» 
entirely with the general experience of pathologists, that 
lesions of both the thalamus and corpus striatum produce n^ 
suits chiefly upon the opposite side of the body ; ' whether 
the symptoms produced point to a disturbance of the kin 
die (motor) or aesthesodic (sensory) tracts. The view originall 
advanced by Carpenter and Todd, that the thalami are 
cemed in the upward transmission and elabonition of sensorj- 
impulses, in conti-adistinction to the corpora striata, which 



e n^ 
rherJ 
lescifl 
lalH 



* Rtire eioeptlona to thU rule in«j be noted, ta in 
(FloobAig). 



Ihe Qftse of Um moior ultsnii 




CENTRAL TUBULAR GRAY MATTER. 147 

are concerned in the downward transmission and elaboration 
of motor impulses, seems to be gaining ground, and many 
facts may be urged in its favor. 

When the cerebrum is removed from some animals, the 
frog in particular, the basal ganglia being left intact, and 
some outward excitation be afterward used to induce move- 
ment in the animal so mutilated, there is every indication 
that the animal can see, because it avoids objects placed be- 
fore the eyes, in case they tend to obstruct its passage.* Its 
movements are those of an entire frog, except that they re- 
quire some external stimulus to call them forth. It can be 
made to crawl, jump, croak, swim, and perform all other acts 
of an automatic machine. It is the effect of light upon its 
movements, however, that has some bearing upon the exist- 
ence of a visual center within the substance of the thalamus, 
since no observer has ever demonstrated that the corpus 
striatum is related either anatomically or physiologically with 
that sense. 

THE CENTRAL TUBULAR GRAY MATTER CONNECTED WITH THE OPTIC 

THALAMUS. 

The prolongation of the gray matter of the spinal cord, 
which lines the third ventricle, is best described in connection 
with the thalamus, although it is structurally independent of 
that ganglion. The following parts have been definitely 
made out : 

1. The inferior optic ganglion. This mass of gray matter 
is situated at the lateral border of the tuber cinereum. Mey- 
nert and Luys describe it as forming an integral part of the 
tuber cinereum, although Wagner considers it as a part of 
the anterior perforated lamina. It presents a distinct sickle- 
shaped outline on longitudinal sections, the concavity of 
which looks forward. Luys thinlvs that the two ganglia join 
in the median line, and that the fibers of the optic nerve 
decussate within them. The opinion of Meynert is directly 

' Snob* an aoimal will OTen try to avoid ttrong thadovct thrown by the sunlight across 
iupath. 




THE BRAIN. 

Opposed to this view. This author advances^ moreover^ 
anatomical grounds for the belief that the fibers of the optii 
tract really belong to the superior projection system <:] 
gnus to the so-called ** radiating fibers^ of the cerebmm) ; til 
the inferior optic ganglion is to be regai'ded as the i»eripli 
extremity of these fibers ; and, finally^ he suggests that il 
some nndiscovered way the fibers will probably be ti 
later to some nucleus of the central tubular gray matter inti^ 
mat el y connected with some other part of the body, per 
the muscles of the eye. If this view be accepted, the mil 
imposed layers of the retina must be considered a^ aiial<| 
to those found in the cortex cerebri* 

2. Within the tuber cinereum, behind the inferior optj 
ganglion, commissural fibers which turn backward withiT 
the centml tubular gray matter may be demonstrated* Tb 
termination of these libers is as yet unsettled. 

3. The posterior longitudirtal fasciculuH ' of the teg- 
mentum cruris may be traced along the central tubular 
gi'ay matter of the third ventricle, the aqueduct of Sylviris 
and the fourth ventricle. It tenninates centraUy in tbf 
broad, thin ganglion \^ithin the "-' substantia innominate 
qfBeiV 

From this ganglion, fibers may be traced into the **extenii] 
capsule " of the cerebrum, the cortex of the operculum, lb< 
fossa of Sylvius, the island of ReD, the claustrum, and cortei 
of the temporo-sphenoidal lobe. The greater mass of the 
posterior longitudinal fasciculus of the tegmentum lies to the 
outer side of the anterior pillar of the fornix, but a few fibers 
from the *'infundibulum'' pass across the inner side of the 
pillan 

4. The descending hrancJi of the anterior piUar t^f the 
fornix lies within the central tubular gray matter of the third 
ventricle. The ascending branch is also similarly imbedded 
before it enters the body of the thalamus, and the same may 
be said of the tipper part of the corpus candicans (mammil- 

' Tbe reader is referred to t Bab§eqi»eDt pi^ Cor tbe complete d«8^fplioia of lltk 

bundle of fibers. 



ANTERIOR PILLAR OF FORNIX, 



149 



ry tubercle). Luys, Arnold, and Meckel believe that the 

descending branch of the cms of the fornix bocomcs fused 

^ith the stria cornea and the habenula conarii. The cms of 

16 fornix makes a remarkable twist npon itself, the loop 

which forms the corpus candicans (mam miliary tubercle), 



njiniiia I 
cinrrca ' 



Ant, Title rcle. 



peduncle of 
pineal mand. 



Th.siip, 



7ulvi 



vtnar 



.pineal 



^10 dand 



11 



2 



12_ 



15 < 



tl. — A diaaram Jm^^l \ 



, . J ifif ttMifii>r fa Mhote tht itmct mr/oM o/ iKi ofttk ihah- 
ffrati maUtr renwved^ itimmnff thf thiri wmirlcU^ and Uir ar- 
t c/ neighboring /MtrU, 

. mtp., fluperior T»ari of thalafiitiR; Th, inf., inferior part of f^ime; m. e^^ ttiiddlo conu 
lDl^f»«n»; !, ■'fceimi of optic comfTti««»TiT ; *i, infniitiibulunj niid pituliiiry body; 8, 
Jill I i'lr enis cif foniU ; 6, ciirpufl can* 

«r I'Atyr; 7, tin' third nerve; H, ltu* 

CrrtH '' 'rii^^iiiinii ; 1^, 

iquc<t< It should b« 

OQlapflJ .,^, -^ ,„:--^ -.--■ ^ ..:..:.^ .: ,..:.-_.. -_ ... 

rhen it n^ic iirs the base of the brain, and returns n* enter 
thf* suljstance of the thalamus (bundle of Vicq d'Azyr).* It 
must not be inferred, however, that the corims candicans con- 
sists only of fibers of the fornix, doubleil upon themselves 

* FoTiel tad Oufld^o deny th&l the fiben of the nnt^rfor pWXmn of \he foniU &tT 
\ with i\totm of Hie biiiidl« of \1oq d'Aiyr. 




THE Bit J 

as nerve-cells are abundant within it, some of wUch ami 
intimate relation with the fibers of the cru8 fomicis. 

It will be apparent, after what has been said, in. a 
lining of the third ventricle represents a prolongation of li 
gray substance of the spinal cord into the brain. By Lajtl 
it is considered as connected with fibers imbedded hAk\ 
within it and the thalamus, which concentrate thet 
around certain nodal points, among which he mentioc 
*Vgrfiy protuberances of the septum, for the olfactory roolfj 
those of the tuber cinereum, for the optic fibers ; tlie nmi 
lary tubercles and pineal gland, for the connecting 6h 
emanating from the anterior centers.'* lie also savic Hi 
similarly receives a certain contingent of gray 
fibers^ which probably represent the centripetal spinal fil 
which are distributed to these plexuses/' 

It is probable, and !)y some authors stated to be deni^^a 
strable, that all of the cerebnd fibers, apparently distribuM 
to the substance of the thalamus, are not connected with tbf 
nerve-cells of that ganglion. Some unquestionably appeii 
to pass througk it to become united \^ith the gray maAsee 
described as connected with the lining tubular gi'ay matter fit 
the third ventricle. In this way the thalamus possibly W 
comes indirectly associated with the gray substance of the 
spinal cord as well as with the sensory tracts comprLsetl with- 
in the 'tegmentum cruris.* It is from this standpoint that 
Lays expresses himself as follows : 

*'From this double induction we are therefore led to csoii- 
sider the masses of gray matter usually described under the 
name of * optic thalami/ as essentially central regions which 
are the bond of union between the various elementsf of th** 
entire cerebral system. 

*^ Through their tissues pass vilirations of all kinds — then 
which mdiate from the external world, as well as those whicl 
emanate from vegetative life. There, in the midst of the 
cells, in the secret chambers of their peculiar activity, the 
vibnitions are diflFused, and make a preparatory halt ; and 
thence they are darted out in all dii^eclions, in a new and 



i 



THE IXTERNAL CAPSULE. 161 

already more animalized and more assimilable form, to afford 
food for the activity of the tissues of the cortical substance, 
which only live and work under the impulse of their stimu- 
lating excitement." 

THE INTERNAL CAPSULE OF THE CEREBRUM AND THE 
DIAGNOSIS OF LESIONS AFFECTING IT. 

In connection with the description of the so-called basal 
ganglia (the '' corpus striatum " and ''optic thalamus " of each 
hemisphere), I have repeatedly mentioned a tract of fibers, 
called the "internal capsule of the cerebrum" * (Figs. 7 and 
12). This band has an anatomical peculiarity, which has 
brought it into prominence with both physiologists and 
neurologists, viz., that it seems to traverse the substance of 
the hasal ganglia without any apparent structural relation 
with the nerve-ceUs found within them.^ 

It is by no means certain that the nerve-cells referred to 
may not, in some indirect manner, be yet proved to modify 
or govern the impulses which travel along the fibers of the 

' Properly speaking this band of fibers should be named the ** internal capsule of the 
lentieular nueleu$.^* 

' The late researches of Flcchsig tend to prove that a direct communication exists 
between the motor area of the cerebral cortex and the spinal cord, without any interven- 
tion of the cells composing the basal ganglia. The so-called ** pyramidal tracts " have 
been traced by this observer (1) through the middle third of the internal capsule (pos- 
terior to the ** knee '') ; (2) through the median part of the motor half of the cms ; and 
(8) as two strands, one of which decusnates and the other as a direct bundle, in tlie 
medulla. 

The non-decussating or direct bundle is continued into the cord as the so-called 
•* coiitmn of TtirekJ^ or the ** direH pi/ramidal column?^ The decussating bundle, which 
ts much larger than the direct, is prolonged into the spinal cord after crossing to the 
oppoaite side of the medulla, as the so-called " erosted pynufnidal column,^^ It occupies a 
distinct area in the lateral column of the spinal cord whose position changes somewhat 
at different altitudes. Finally, the pyramidal tracts are found to give off fibers to the 
anterior ganglionic cells of the spinal gray matter, chiefly in the cervical and lumbar en- 
largements of the cord. In thi.s way they connect the brain with the motor ccUs^hicfly 
thoae associated with the muscles of the extremities, in contradistinction to those of the 
tnmk. 

The method of arrangement of the fibers of the internal capsule, when the level of 
the cmsta is reached, seems to bo comparatively uniform. Those that spring from the 
motor regions of the cortex pass down the median part of the cnista ; those composing 
tho ''genu** or knee of the internal capsule pass through its central part ; some from the 
* portion of the capsnlo lie in the lateral part of the crusta. 



THE BRAIN. 



internal capsule (as we have every reason to beliave tlieyt 
in the case of other fibers which pass from the cortex to 
crQS, pons Varolii, and spinal cord) ; but, at present, we 
compelled to admit that this region appears to afford 
only direct communicaiion between the convolutions 
parts below the cei*el)rum/ because any inteixention on the 
part of the corjms striatum or the optic thalamas has m 
been conclusively demonstmted. 



f 



itlV: 




y\ 



FiO. 38. — A tU(tifrno\ deMffnrfl htf th^ author to «hoiB thf rtialioiu uf (he tnifmai 
tuU of the crrrltrum to d^nrrnt ^tntcture* nVt^ri from above, 

Tbc BPOtioD of the brain lins been Tniide horiiontaUff in a plane to intersect the biual gia- 
glm. C. N,f caudate uucleuii of corpus »tHatum ; L. K., leiKiculur nuclcuit of th^ i 
with it* ihree part? («^ ft, *'\ ; 0. T., optic thalamus ; S, fos^a of Hvlviii* ; C,, 
trtJtn; E. C, eitei-ual cBpaule of i^rt'brum ; i, », t^ convolutions of thi? l»tm 
Bed; rtj //, c, the iuner^ ini<Idl«% aa<J cxt*^niftl mcnibur of the ientknilar nuctir 
anterior limit of the internal capt^ule ; 2, '^ knti* ^^ or tM?nd of the «amc ; S^ p^ 
limit of the @amc; 1-2, **caudo-U'micuIar" portion of the capsule ; 2-i, 'Mhftli 
lenticular ** portion of the ^me ; ¥\ crura of fomU, the fifth Tcutiiclc Iring i 
and the third Tcntncle behind it ; t. (.,, 9«pturo luciduio, t^howing Us two lajre 
fifth ventricle between them ; m. <r., iniddl<i cororoi&sure of the thahiiuuB ; ji, j 
gland and its pedunclea ; n, ntxtea cerebri ; f, tc.'^tcs cerebri. 

This tract seems to be a continuation upward of both the j 
motor and ^en^ory portions of the crns (the ** basis craria^^V 
and '*tegmentTira crnris,-' -* ^'^ — "-^^^ ****'^ *^ ^'^^ — *- 




■' of Meynert) into the white sub- 
stance of the cerebral hemisphere of either side, where its 
fibers diverge and pass to the convolutions. It forms the, 

i The fibers of the '^ external captule of the oerebmin " mtky be an eiception (F1^ 



THE INTERNAL CAPSULE. 153 

greater part of the so-called ^^ corona radlata," which were 
described in a previous page ; although, properly speaking, 
the internal capsule ceases at the optic tracts below and the 
upper level of the lenticular nucleus above. If we trace the 
anterior fibers of this bundle from below upward, we shall see 
that it divides the corpus striatum of each hemisphere into 
its two portions, the caudate and lenticular nuclei. The pos- 
terior fibers of the internal capsule separate the lenticular 
nucleus from the optic thalamus of the corresponding side 
(Fig. 38). The diagram, to which I now direct your atten- 
tion, will make the relations of this bundle apparent, while 
it will also show the peculiar angle or bend which the in- 
ternal capsule exhibits in all horizontal sections of the brain 
which intersect the basal ganglia. The fibers that form the 
" caudo-lenticular " portion of the capsule are imperfectly 
understood. We have no positive evidence of their motor 
function. The pyramidal tract lies i)osterior to the "genu" 
of the capsule, as do also the motor fibers of the face. Back 
of these tracts we encounter the general sensory tracts. The 
optic fibers appear to lie still farther back, passing to the 
occipital cortex (see Fig. 39). 

Again, if a cross vertical section of the cerebral hemi- 
spheres be so made as to include the substance of the thala- 
mus and the lenticular nucleus, it will be perceived that the 
peripheral outline of these two masses of gray matter may 
be compared to a square ; and that a diagonal band running 
from the outer and ui)per comer to the lower and inner cor- 
ner of this square corresponds to the situation of the "in- 
ternal capsule," which is included between these ganglia. 
Above the level of the basal ganglia, the fibers of the internal 
capsule radiate to join certain convolutions or "gyri" which 
will be enumerated later. Thus it is that the fibers which 
compose the internal capsule appear in most of the cross- 
sections of the middle zone of the cerebrum to bear a fancied 
resemblance to the handle and sticks of a Japanese fan ; the 
handle being the constricted portion between the corpus 
striatum and the optic thalamus, or the capsule itself, and 



154 



THB BRALW 



the diverging fibers being located within the mednlliii^ 
of the cerrbnil hemisphere. 

The extension of sensor y flhers from the tej^mentaii] 
upward mthin the internal capsule ol the cerebrom is now I 
clearly j)roved as is the continuity of the motor tract am« 
orly. The coui'se of the former ha3 been studied by dis 



"cji 



Fio. 39, — A diagram dm^ned h^ ihe authitr (o thow the mhdivmont af fhf 

mpsule, 

a^ ilie portion wbich \ic9 iinUTiorly l<> the knee of the taji^nle. The faiictiaof of Ha 
iihers which compose this portion are not, na ret, deHttitely dcC4;rmfn>^<l 
fibens for the face; m, the fibers of the focAlled "motor tmet"; », t" 
"sensory tract**; #, f, those of the "speech imct**; o^ Uio^e of li»«? ***.; 
The fibers of each trAct are prohahly asaociaitMl with both sid*« of tht* boU^, ^li^ 
cbii>fly with the opposite nidi.*. 

tion, embryological investigation^ physiological exj^erimealt 
and, finally, by the examinations of pathological proc^eraeft. , 
It has been Hho\iii by Turck * that, when certain convoliiiic 
of the brain (chiefly those which are motor in function) hat 
suffered partial or complete destruction, that a desceri 
degeneration follows the course of the nerves which arei 

^ This author first made known Ids great discover; lo the Acadcmj of Sekoic 
Yicuna, in 185L 

• Dcg!cncfation of ncnrw follon^, aa a rule, the direction o/ the eurrmiU wekUh mn 
norma/iv convrffed bit tlum. Bj t\\U meawi, Uio qiifiation of the atTefciiC or 
eharactGr of certain nenre-tract^ has txrcn poaltivefy deddod. 



METHODS OF TURCK AND WALLER, 155 

Bected with the cells of the injured part. This degenerative 
process extends along the nerves, from the cells of the cortex, 
to their peripheral terminations, in the cells of the spinal 
gray matter; thus enabling a careful observer to trace the 
paths of the fibers with even greater accuracy and positive- 
ness than the most skillful dissector could possibly hope to 
attain. By means of this fact,* amplified somewhat by 
Waller and Gudden, physiologists have been enabled to solve 
many problems regarding the origin and course of special 
nerves, as well as certain nerve-tracts within the spinal cord 
and brain, which could not otherwise have been determined. 

Although the remarkable observations of Turck were 
given to the profession some years before Waller was awarded 
the honor of meriting recognition as the recipient of the 
Moynton Prize for Experimental Physiology, his paper re- 
mained comparatively unknown for some years, when its 
great value at last became recognized. 

The difference between the discoveries of Waller and 
Turck lie in the fact that the observations of the former were 
confined to the results of artificial section of spinal nertes^ 
made for the purpose of studying the effects of such injuries, 
while those of Turck were of a purely pathological character, 
in which the results of old morhid deposits vyithin the sub- 
stance of the brain were studied by the aid of successive sec- 
tions of the brain and spinal cord at different levels, which 
could be contrasted with each other. 

Both of these observers arrived at the same fundamental 
law, viz., that injuries of nerves or of nerve-tracts which sep- 
arated them from their centers of nutrition or trophic centers^ 
canse a degenerative process which extends along the sei)a- 
rate nerve-fibers to their ultimate ramifications.* Waller's 

' The retder in referred to a lecture upon the " Wallcrian Method of Rcaonrch," by 
Prof. Dalton, " Med. Record," Feb. 11, 1882. 

' Nonre-6bcr8 degenerate only when pevcred from their connection with Boine special 
nenre-oenter, from which they receive their nutrition. Tho*»c are called the ".trophic 
oenten " of the dilTercnt bundle;*. When once cut off, the de;!cnorativc proccBs extend^) 
throughcmt the entire length of the nerve ; unlcsH it meets another nerve-center (some 
ganglioolc miu of gray substance) interposi.'d in itn (>our}>e. It seldom, therefore, if ever, 
extends from spinal nerre-tracts into the Bpinal nerves, or vice verm. 



THE BRAIN. 



experiments were confined exclusively to the spinal 
and resulted in the foUowing deductions : 1, That ii tlie i 
was divided at its exit from the vertebral canal, all of iU \ 
mate fibers degenerated for its entire length ; 2, that i( 
anterior root of the nerve was alone divided, only tlie m^ 
fibers degenerated ; 3, that if the posterior root of the ne 
was severed outside of its ganglion, the sensor */ Jihtrs of 
nerve degenerated and the motor fibers remained uuaffectoijj 
4, that if the posterior root was divided ifiternal to H^ \ 
glion, the nerve outside of the ganglion did nofc de^nenUlj 
but the portion which was stUl attached to the spinal 
but separated from the ganglion, suffered complete dc 
tion. Prom these data, this observer was enabled to lay \ 
the geneml law that the nmtor fibers of the spinal twt^m i 
dependent frr their struetaral lutegrltif upon (heir caui 
tion with the spinal cordy while the sensory ner^e-j 
depend upon their connection with the spinal ganglia. 

The degenerative process which was recognized by K)!h 
Tiirck and Waller consists in the segmentation of the my etis 
and the production of an excess of nuclei along the course ii 
the affected nerve-fibers. The unaffected fibers retain their 
normal appearance, and thus define the diseased bundles 80 
that they can H[>e traced along the spinal cord and peripheial 
nerves with gi'eat accuracy. 

Tui'ck was enabled to demonstrate for the first time a life- 
tine tion between the anterior and posterior segments of the 
lateral crjlumu of the spinal cord, which no ordinary dissec- 
tion could possibly have established. The observations of 
Turck have been supplemented by those of Oudden^ Golo; 
Gull, i^lechsig, i[eynert, Rolando, Stilling, Foville, Gratiolel; 
Broadbent, Bourdon, Charcot, Spitzka, Starr, and others, who 
have added much to our knowledge of the situation and func- 
tions of the various spinal nerve- tracts. 

OudderCs method of anatomical research consists in ih^ 
destruction of nerve -tracts by opemtions performed n| 
neiDhj-horn animals. He found that^ as a result of the inj 
done, the proximal end of the divid*^d nerve atrophlec 




METHODS OF OUDDEN AND FLECH8I0. 167 

foeU as the central connections of the nerve. The so-called 
Wallerian degeneration, of course, affects the distal portion 
of the nerve, simultaneously with the development of Gud- 
den's degeneration of the proximal portion. 

Flechsig's method consists in studying the relative period 
(daring fetal development) at which certain nerve-strands 
acquire myelin. 

Thus we have to-day the older methods (1) of actual dis- 
section of nerve-bundles in partially hardened specimens, and 
(2) the comparison of a consecutive series of fine sections of 
the brain and spinal cord with each other, supplemented by 
the more accurate methods of Turck, Gudden, and Flechsig, 
as guides in our anatomical studies of the nervous system. 

The study of microcephalic brains, although yet in its 
infancy, bears evidence of affording great possibilities in the 
future toward the elucidation of disputed i)oints in cerebral 
and spinal anatomy. M. Allen Starr has lately reported a 
very interesting case of this character. 

The fibers of the caudo-lenticular portion (Fig. 38) are prob- 
ably deflected (in the pons) and pass to the cerebellum. The 
remaining fibers which lie anteriorly to the sensory tract are 
not so deflected. 

Now, because motor fibers carry centrifugal impulses, it is 
logical to describe the motor bundles of the internal capsule 
from above downward, beginning with an enumeration of 
the convolutions from which the motor fibers are believed to 
spring, and tracing the course of these fibers to their connec- 
tion with the cells of the anterior horns of the spinal gray 
matter, while it is customary to I'everse the method, in case 
the sensory fibers, which carry centripetal impulses, are under 
consideration. 

The diagram to which I shall first call your attention (Fig. 
14) was designed by its author (Seguin) to rudely represent 
the general features of the internal capsule. It is impossible 
to properly portray all of the more important facts, to which 
I shall call attention, by any form of schematic drawinj: ; so 
that the diagram offered, which is most ex(M'll(Mit of its kind, 

18 



158 



THE BRAIN, 



can not more than afford general hints of value, and fibua 
be used as a guide only in oontraf^t with more elaborate tm\ 
found in standard anatomical works. 

The motur bundles arise from the cells of the cereb 
cortex comprised within the convolntions of the middle i 
of the brain. This region— the so-called *' motor district* - 
includes tlie ascendiuf/ frontal gyruHy the ba^i^ of the fir 
secofid^ and third frontal gyri^ the ascending parietal ffyn^ 
the paracentral lobule, and the supramarffivul gyrujt' (1 
22), Some of these bundles pass directly into the subst 
of the caudate nucleus, some into the lenticular mirleua 
possibly a few into the optic thalamus of the correspol 
hemisphere, after traversing the medullary center of the* 
brum ; but the majority appear to pass directly into 
anterior portion of the thalamolenticular division of the I 
temal capsule (Figs, 38 and ^9). 

The Bensory fibers which are comprised witliin the 
ternal capsule are prolonged upward from the posterior p 
of the cms (tegmentum cniris cerebri— Fig, 8) to the coii^ 
volutions of the occipital, temporo sphenoidal, and parielil 
lobes. It is believed that the posterior third (or sensory pot- 
tion) of the internal capsule has connections also, by means iif 
the optic, olfactory, gustatory, and acoustic nerves, with the 
peripheral organs of special sense. Physiological experiment 
has shown that, when certain convohitions of the sensory 
regions of the cerebral cortex have l)een destroyed in animals^ 
the senses of sight^^ smell, hearing, and taste have l>een either 
temporarily or permanently impaired. We know also ibMt 
total hemian«esthesia results from lesions, both in man as weU 
as animals, which involve the posterior third of the intc^ 
nal capsule. The impairment of special senses from cortical 
lesions, momover, appears to be confined chiefly to the side 
opposite to the seat of injury, in case of unilateral destruc- 
tion of the cerebi-nl convolutions— phenomena which point 
strongly to a decussation of these fibers, in which respect they 
bear an analogy to the common sensory tracts. Future con- 

^ The («rni ** gyruB " is Bjnonymout iHtb ** oo&TolittloQ." 



CONSTRUCTION OF INTERNAL CAP8ULR 169 

sideration will be given to these points. Some of them, 
particnlarly bearing upon the location of an olfactory, optic, 
and acoustic center, within the substance of the thalamus, 
have already been discussed at some length in previous 
pages. 

When we discussed the corpus striatum, I constructed for 
you a diagram which represented the afferent and efferent 
fibers of that ganglion, in which the motor fibers of the inter- 
nal capsule were shown (fig. 40). I stated at that time that 
the functions of the caudate and lenticular nuclei were still 
unsettled, but that physiological and pathological facts could 
be advanced to sustain the belief that the cells of both halves 
of that ganglion exercised a modifying and controlling influ- 
ence upon motor phenomena, and were probably the seat of 
automatic action, irrespective of the cells of the cerebral cor- 
tex. I stated, also, that it was probable that the cerebel- 
lum had a direct connection with the ceUs of the caudate 
nucleus, and that physiological experiment pointed strongly 
to cerebellar innervation of motor acts, because disturbances 
in coordination of movement are produced by disease of the 
cerebellum, and motor acts appear to be weakened. Now, 
because experiments made upon the caudate and lenticular 
nuclei can hardly be said to have afforded results which can 
be made the basis for positive deductions resi)ecting the func- 
tions of each, it seems highly probable that the cerebellar 
fibers are in some way connected with those of the internal 
capsule, which are unquestionably associated with motor phe- 
nomena. 

Among the afferent fibers of the corpus striatum, in addi- 
tion to the cerebellar fasciculus (fibers of the processus cere- 
belli ad cerebrum)^ may be mentioned the ** corona radiata "/ 
the ^^ stria cornea^; fibers from the cortex of the ojfactory 
lobe; and fibers from the septum lucidvm (Fig. 40). If it 
can be shown that these five sets of afferent nerves become 
associated with those of the internal capsule, it will help us 
to better interpret the functions of the parts. Spitzka hap- 
pily remarks that '* the time has passed when any single ex- 




Fta. 40. — A Sagiram detti^eii to fhote tAt n/ffrtnt and fffft^ fi^*** 9f ^ 

»frialum and i/i^f o/ the tnimtai m/mt/n, 

C- ^., ** caudme nucleus,** or venliietilni" p<^irttim of o<»r|m8 etnntuTn ; L. X,^ tent] 
nucleue/^ or cxtni-veoiriculiif jwrtjoo of oorpiii^ Mrintntn ; A-Ilt iimliAii Hue, fti 
ing ceriibrnl hemi^pheros; P-^F^ ppyclio-inotor resionj* of ihc <'<trtc-* ; n, ^^n 
fibers connected witii L. N, ; &, fiherfl of the so-^^lled " int^meil cjif>«ii]c ** ; e, I 
cx>iinecicd with C\ A". ; 0^ olfAclory fillers. 

masses (\rithoiit any apparent association with the cells 
bedded within them) in oitier to terminate in remote 



^hi^k 



^nn^ 



CONSTRUCTION OF INTERNAL CAPSULE. 161 

It has been conclusively proved also that special centers are 
sometimes interspersed between these nerve-bundles, so that 
it is illogical to attribute every phenomenon caused by an 
intra-cranial exi)eriment to a disturbance in the activity of 
any si)ecial center." 

The physiology of many parts of the brain is far from 
satisfactorily marked out. Many glaring contradictions are 
apparently proved by the experiments of different investiga- 
tors, and the statements previously made will help, to some 
extent, to explain them. I pointed out, when discussing the 
structural anatomy of the thalamus, that, until the existence 
of the special centers, which are believed to exist by some 
authorities within that ganglion, could be positively demon- 
strated, it will be maintained by others that many phenomena 
which accompany lesions of the thalamus are due entirely to 
pressure exerted upon the adjacent internal capsule. This 
view is held also by many neurologists, when phenomena 
provoked by any exi)eriment upon the corpus striatum * are 
adduced to prove a special function as located within that 
ganglion. Pathological research has, in some instances, 
seemed to oppose the view that the lenticular nucleus pos- 
sesses any important motor functions. The French experi- 
menters, Franck and Pitres, published, however, in 1878, a 
most brilliant attempt to demonstrate conclusively that cer- 
tain fibers of the internal capsule were continuous with the 
motor convolutions of the cerebrum and conducted motor 
impulses. These physiologists found that when the white 
substance of the cerebral hemisphere, which underlies the 
motor convolutions, was faradized, muscular movements were 
created on the opposite side of the body, in definite regions 
corresponding to the supposed action of the so-called '* motor 
centers " of the cortex. It must be confessed by all that these 
observations, which are considered by many as a final proof 

> It in poMible that the caudate nucleus^ when seriously impaired bj leMon8, may cauHO 
boroiplegiA and secondary dej^eneration. (*harcot claims, howev<>r, that tlic effects of 
i MB u i m r ha ge of the corpus striatum arc to be attributed entirely to pressure upon the 
• fibers of the Internal capsule. 



THE BEAIN. 



of the distribution and function of this handle of fiberSi 
among the most satisfactory which ha\^e been as yet 
corded* 

Before we pass to the consideration of the ioternal ca 
in ita practical aspects, let ua »peak a little mure definitely is 
regard to its exact situation and limits* This bundle, as iny 
stated before, lies between the lenticular nucleus on Iht? Mt 
side, and the caudate nucleus and the optic thalamus on tie 
other. Transverse vertical sections of the cerebrum show tliit 
the lenticular nucleus lies external to and below it, while tte 
caudate nucleus and thalamus lie internal to and above it 

In the region of the base of the cerebrum, the head of 
caudate nucleus becomes fused with the lenticular nuelem 
so that the internal capsule does not extend to the extiemi 
anterior limits of these ganglionic masses. The posterior limit' 
of the internal capsule is probably defined by the termina- 
tion of the lenticular nucleus, the thalamus being- prolonj 
beyond it into the substance of the cerebiul hemisph 
Above the level of the basal ganglia the fibers of this hundto 
radiate into the different lobes of the cerebrunK mul »x* 
be "capsular fibers," properly speaking. 

To the naked eye the fibers of the internal capsule, w] 
pass between the ganglionic masses at the base of the beiiit* 
sphere, appear to be continuous with the corona radiata abore, 
and the fibers of the cms cerebri below. There is a beliel 
among some anatomists, however, that successive loops will! 
probably be demonstrated by more extended research — th# 
fibers of the crus leaving the internal capsule to join the odla 
of the basal ganglia, while others leave the ganglia to pas», bj 
means of the iuternal capside, to the cerebral convolutions. 
The results lately obtained by Fmnck and Pitres, from an 
experimental standpoint (mentioned on a i)receding page), as 
well a^ those lately published by Flechsig, from investigatio» 
made upon the fetal brain, seem, however, to be rather op- 
posed to this view, although they perhaps do not positively 
controvert it. This point cannot be positively decided until 
the functions of the basal ganglia am determined. 



I 




LESIONS OF INTERNAL CAPSULE. 163 

EFFECTS OF LESIONS OF THE INTERNAL CAPSULE. 

The situation of this bundle of nerve-fibers renders it liable 
to become directly involved when haemorrhage, softening, or 
tamors of the central portions of the hemisphere exist ; or, 
indirectly, when these conditions affect the caudate nucleus^ 
the lenticular nu^leuSy or the optic thalamus. 

The most frequent seat of cerebral apoplexy is the corpus 
striatum ; because that ganglion is extremely friable and very 
vascular. The optic thalamus probably ranks next in the 
order of comparative frequency. The blood-vessels which 
enter these bodies ' through the anterior and posterior perfo- 
rated spaces at the base of the cerebrum seem to be frequently 
affected with atheromatous degeneration and miliary aneu- 
rysms,' and are often ruptured when subjected to any unnatu- 
ral strain. Nature has given to the carotid and the vertebral 
arteries a remarkable tortuosity before their entrance into the 
cavity of the cranium, in order, as it were, to diminish the 
liabUity to rupture of blood-vessels by decreasing the velocity 
of the flow when the heart's action is excessive ; but even this 
mechanical safeguard is not always sufficient to protect the 
intracranial vessels from rupture when extensively diseased. 

Again, the condition of softening may result from embolic 
obstruction to some branches of the catotid (usually of the 
left side),* because the nutrition of the parts supplied by the 

1 The motor regfons of the cortex are supplied by the middle cerStral artery ; the 
nodeufl caadatos by branches of the antet-ior cerebral and anterior communicating arte- 
ries ; the lenticular nucleus by the middle cerebral ; and the optic thalamus by branches 
of the middU and poderior cerebral vessels. 

' The Teasels mott frequently affected with aneurysmal dilatations are the internal 
earotid, basilar, and middle cerebral. Within the cavernous ninus large aneurysmal 
tamons are not unoommon. It must not be supposed, however, that the smaller vessels 
of the brain are exempt. Miliary aneurysms, which give to an artery and its branches 
an appearance resembling a bunch of grapes, frequently afToct the vessels that form the 
drde of Willis, jmd even those of the pia mater within the substance of the brain and in 
the Tcntricles. The small vessels which nourish the corpora striata and the optic thalami 
atesometlmet affeoled. 

Miliary aneurysms frequently coexist with aneurysmal tumors outnido of the cranium, 
bat they aeem to exhibit an independence of atheroma which is quite remarkable. 

* The reasons for this fact can be found mentioned in a hitc work by the author — 
«* Pnidkal Medical Anatomy." William Wcod & Co., 1882. 

? 




Finally, tumors soraetiraes develop within the cerebral 
hemispheres, and create pressure upon, as well a« destmctic 
of, important nerve-tmcts. Time will not permit \m to ente 
into detail respecting all the diagnostic poinrs by which th< 
existence of each of these conditions may be recognized durio 
life, I direct your attention, therefore, only to sneh points ; 
are of imx^>rtance in the diagnosis of disturbance of the mi\ 
posed functions of the internal capsule. 

It may be stated with some degi*ee of positiveness that, if 
the anterior part of the '' thalamodenlicular" division of the 
internal capsule (Pig, 38) l>e affected, a hemiplegia nf ili« 
opposite side is developed.* This is more or Jess conipletnJ 
according to the seat and extent of the lesion which causes itJ 
The exciting cause may possibly be situated within the ante- 
rior or middle portions of the white center of the cerebnl' 



' ExcvptiuiLS to llii^ rule nrt oooa^ioniitW ob^rr^d. Tht h4?iii[|)1«);iii« io rare 
v\ht9 on Ibc sRmo wie us Uie Imon. The ^iplAflfttlon of iUh tttct Um been tbown, \tf, 
the roseiirche«« of Flechsi;i, to lie id the Taryin^ pro|(ortiomi of tho dirvct ixul doo 
fibers which piiB« from the cerebrum to the »pliia] oord. 




LESIONS OF INTERNAL CAPSULE. 165 

hemisphere, above the level of the basal ganglia, in which case 
it will interfere with the normal action of certain bundles of 
the internal capsule which spring from the motor convolu- 
tions of the cortex previously enumerated. Again, it may be 
situated within the constricted portion (the capsule projyer), 
in which case bundles of nerve-fibers, functionally associated 
with widely diffused areas of the cortex, may be affected by 
a lesion of small size. Finally, it may be apparently confined 
to the substance of one of the two nuclei of the corpus stri- 
atum (Pig. 40), or the optic thalamus, and still exert sufficient 
pressure upon the constricted part of the internal capsule 
to produce more or less extensive and complete paralysis — 
chiefly of the opposite lateral half of the body. The hemi- 
plegia of intra-cerebral lesions forms, as a rule, a striking 
contrast with the various types of monoplegia (p. 86), which 
are produced by circumscribed lesions of the cortex. The 
latter are often of the greatest aid to the neurologist in local- 
izing the seat of the exciting cause.' They have been dis- 
cussed in preceding pages. 

The second symptom which may indicate a lesion of the 
internal capsule is hemi-ancesthesia. By this, I mean a loss 
of sensation, more or less complete, which is confined to the 
lateral half of the body. It exists (save in rare instances) 
on the side opposite to the seat of the lesion. 

This may occur when fibers of the sensory tract of the 
internal capsule (Pig. 39) are destroyed or impaired by dis- 
eased conditions directly affecting them, as noted by Charcot, 
Raymond, Rendu, Perrier, and others, or by the pressure 
exerted by lesicms situated in parts adjacent to them. It is 
asoally accompanied with a slight form of motor paralysis ; 
probably because a few of the motor fibers of the internal 
capsule are, as a rule, simultaneously interfered with. The 
tests by which this condition may be recognized are, doubt- 
less, familiar to you all. No examination of a patient afflict- 
ed with i)araly8is is ever complete unless sensation, as well 

' The term coren nuuij forms of paralysU) where ttpfcial grfmjm of muscles are alone 



1G6 ^^^ THE BRAJN. 

lis muscular power, is carefully tested, before a diagnosis 
made* 

A third symptom of lesions of the internal capisiik ■ 
eludes a variety of manifestations of impairment of the 
cial senses. 

In connection with the discussion of the optic thahmi 
you will recall the views advanced respecting the \HWsk\ 
of existence of special ceutei*s of smell, sight, hearing, ai 
sation within the substance of that ganglion. Clinical far 
point strongly also to a relationship between nene 81 
related to certain special-sense perceptions and the inli 
capsule. We are forced to admit that some of the fibere 
the posterior part of the internal capsule probably haf* 
direct or an indirect associatiun with smelly sight, hesinm^^ 
sensation, and perhaps of taste also. In a subsequent secti(»ivi 
many interesting facts in physiology, which shijw the vulnt] 
of abnormal phenomena in smell, sight, speech, hearings tftsti^l 
etc., upon the diagnosis of intra-cranial lesions, wiJ! be gt?aL 
Many of these might be mentioned hei'e with advantage, 
if space would permit. Charcot has endeavored to expfaib 
a statement, that has until lately been accepted, vix., that 
hemianopsia* seldom (?) occurs in connection with lesions of die 
internal capsule, but an amblyopia is developed on the same 
side as the cutaneous an^sthe^ia^ with a remarkable coutiat' 
tion of the field of vision and difficulty in discriininatiun ol 
color. The explanation which this author made of this stilts- 
ment is, that a second decussation of the fibers of the optic 
nerve takes place somewhere between the optic chiasm and 
the internal ca^^sule, probably tu the tnbert^ula qtuidrigemina. 
Some late discoveries of Munk and Wernicke (coupled iiith a 
collection of autopsies beurlu^ npon the subject) have caused 
this authfir to mi^difv his views. It is now considered la 
questionable if many case^ reporte<l as exhibiting amblyopia i 
during life, were not affected with hemianopsia. This sabjedfl 
will be discussed in connection with the corpora quadrigemina. 



^ The torrn " li«mi(>|xi* ** iC\^\^^ ImU «iglls h t m^mm ^ mcinf m blitnlniNM of oM 
hmif of Um; rvUnau The Utter i*, llMMbns tlw fiNlbmMfi trrtn b iWs cotioection, ^^ 




LESIONS OF INTERNAL CAPSULE. 167 

When the radiating fibers of the internal capsnle are in- 
volved in a lesion which creates a gradually increasing press- 
ure (as in the case of tumors which grow slowly) the fundus 
qf the eye exhibits morbid changes in the region of entrance 
of the optic nerve which are of value in diagnosis. The con- 
dition so produced is commonly known as the " choked disk.^^ 
It is nearly always bilateral, but often most marked in one 
eye. It may be considered as one of the most positive signs 
of an extensive intra-cerebral lesion, and especially of tumors 
of the brain. 

When such an eye is examined with an ophthalmoscope, 
the condition found is characterized by a swollen appearance 
of the optic nerves, which project appreciably above the level 
of the surrounding retina ; the margin of the disk is either 
obscured or entirely lost ; the arteries appear small, and the 
▼eins large and tortuous; finally, small hemorrhagic spots 
may often be detected in the retina near the margins of the 
disk. 

In spite of this condition, the power of vision may be little 
impaired; so that the existence of ** choked disk'' may be 
unsuspected unless the ophthalmoscope be used before the 
diagnosis is considered final. 

After a number of weeks, and very much longer if a tumor 
is the exciting cause of the condition, the appearance of the 
disk changes. An unnatural bluish-white color, which de- 
notes atrophic changes, develops ; the outline of the disk 
becomes sharply defined ; the retinal vessels become small ; 
and vision becomes markedly interfered with. 

In exceptional cases of destruction of the internal capsule, 
the sense of smell has been abolished on the side opposite to 
the seat of the lesion. This fact requires special considera- 
tion, as it has been shown that the center proper for olfactory 
I)erceptions seems to be in the hemisphere of the same side. 
Meynert and Gudden claim, however, to have demonstrated 
the existence of an olfactory chiasm in the region of the an- 
terior commissure, in animals where the bulbs are largely 
developed ; and fibers have been traced in the region of the 



168 



TEE Bl 



^''siddcvZum cornu Ammanis^^* or the tip of the tenif 
sphenoidal lobe, which connect the olfactory centers 
each (ither. The experiments of Perrier tend to disf 
the decussation of the olfactory paths in the anterior 
missure ; so that the question still remains unsettled, 
sense of smell is more commonly affected in the nostril 
the side wliich eoiTesponds t^ the seat of the lesion.' 

Among the fibers of the intenial capsule which are 
tributed to the temporo-sphenoidal lobe some appear to hU 
some association with the sen^e of hearing ; but exiwerii 
tion npon animals to determine the exact seat of the 
of hearing nnd the effects of tlieir destruction are exeeecll]i| 
difficult, because the evidences of impairment of this wii» 
are more or less vagne, Ferrier thinks, however, tliai tW 
superior temporal convolution is unquestionably connected 
with acoustic perceptions. The area which he maps out u 
acoustic in function is quite extensive. 

The region of the hii)porampus and the posterior paijet 
convolutions seems to be chiefly connected with txicfilr. len' 
sihilitt/^ because their destruction has been found to cr€«t9 
more or less loss of that sense on the opposite side ol 
body. 

As regards taste^ the results of experiraentndon upon tW* 
monkey tribe seem to point to the lower portion of the mid 
die temporal convolution as the pmbable seat of the cenl« 
which are related to that sense/ When this region is sa\ 
jected to irritation, certain reflex movements of the li| 
cheek, and tongue are observed, which seem to point to 
excitation of the gustatory sense. Its destruction apj 
ently causes an abolition of taste. 

We have now considei^d three of the more prominei] 
symptoms which are produced by lesions of the intei 
capsule^ and I pass to a fourth, which I believe to be of 

* FcrHer reports a cttM wbore smell aud tute were eimullixieou«l7 iboU*be<l 
blow upon the top of the bead. Ogle reoords ■ oiiiiilar ImitanM. 

' This iDAv help \o exptmii the fact that injuriea reocir<9d upon the vert4*x and < 
protiiberatice cause, in somt* instance^ an alwlitioti of ta»tts ibe tcmporml lob« 
injurod by ooneuaaion againft the adjaoeot bone. 



CONJUGATE DEVIATION OF EYES AND HEAD. 169 

value in aiding the recognition during life of an extensive and 
rapidly developing lesion of the white center of the cerebral 
. hemisphere, viz,, covjugate deviation of the eyes and head. 

When, in connection with rapid softening or an extravasa- 
tion of blood into the substance of the cerebrum above the 
level of the basal ganglia, this peculiar symptom is developed 
(either simultaneously with or following paralysis and coma), 
the patient's head and eyes will be observed to be turned con- 
stantly away from the paralyzed side and toward the side 
which is the seat of the lesion. Various attempts have been 
made by late authors to throw discredit upon the clinical 
significance of this symptom as i)articularly indicative of a 
lesion of the cerebral hemisphere, but I am convinced that it 
is a valuable differential sign. Ferrier has demonstrated that 
a cortical center, * which he locates in the first and second 
frontal gyri near to their bases, presides over conjugate move- 
ments of the head and eyes, and causes dilatation of the 
pupils. He attributes this symptom, when occurring in con- 
nection with hemiplegia of cortical or ganglionic origin, to 
the unantagonized action of the corresponding center of the 
uninjured hemisphere, thus explaining the fact that the dis- 
tortion is toward the side of the lesion. Clinical evidence of 
the correctness of this view has been brought forward by 
Hughlings-Jackson, Priestley Smith, Chouppe, Landouzy, 
Carroll, and others ; and, in some cases reported, the situa- 
tion of the lesion has been verified by pathological observa- 
tion. The opportunity to recoixl pathological observations 
upon cases where this symptom was well marked during life 
has, unfortunately for science, been a comparatively r.ire one. 
It is impossible, therefore, to speak positively concerning the 
diagnostic value of this symptom, although the weight of 
clinical evidence seems to be strongly in its favor. 

A fifth symptom, which jxnnts strcmgly to an existing 
lesion of the internal oii]»sule, is choreiform, moveincnts fol- 
lowing hemiplegia or hemiana^sthesia. These movements 
vary in type and degree. In some oases, the movements ex- 
hibit the peculiarities of athetosis, the fingers or toes being 



ITD 



THE BiUJS\ 



thrown into active motions which cannot be controlled 
the patient ; in others, true ataxia majr he developed ; 
the spasmodic movements partake of the character of 
nine chorea ; finally, a tremor, more or less marked, mav I 
detected. 

It is not uncommon to find that both hemiplegia 
hemianfesthesia may co-exist with these i>ost-paralytic fo 
of spasmodic disease ; bnt one usually overshadows the othe^ 
the hemiplegia being, as a inile, the more marked. How^ 
are to explain these late phenomena, is not definitely set 
They are probably to be classed with other morbid manife 
tions which pamlyzed muscles sometimes exhibit, chielly I 
of *'late rigidity" so often seen, concerning the ean^e 
which many conjectures have been advanced, but nothing ( 
a positive nature demonstrated. 

Finally, it has been observed that lesions of the iot 
capsule, if very extensive, are often followed by a wry 
marked rise in the temperature of the body, W© hare yiC 
much to learn concerning the vaso-motor centers which ire 
variously disposed within the substance of the brain aod 
spinal cord. 

The fact has been mentioned that certain fibers of the, 
inteiTiEil capsule are anatomically related to the cells in til 
motor coiivolufions of the cerebral cortex. Although there s 
still some neurologists of note who deny the value of the lale 
attempts of Fritsch, Hitzig, Broca, Ferrier, Charcot, Hngli- 
lings-Jackson, Pitres, Landouzy, Exner, Chouppe, Luc 
Wernicke, and a host of others, to locate sj)ecial cent 
within the convoliiti^ms of the cortex, clinical and patho*^ 
logical observations are constantly being brought forward Ia 
support of the more generally accepted views. The re^on 
which enribraces these motor centers appeal's, however, to \m 
somewhat limited. A critical review of recorded cases shows 
I think, beyond cavil, that the white center of each hemi 
sphere of the cerebrum, as well as the cortex, may in sob 
instances be extensively diseased or injured without anj 
motor or sensory results which can be determined. Pa the 



LESIONS OF INTERNAL CAPSULE. 171 

logical evidence seems to demonstrate, however, that the re- 
gion so impaired must not be situated where the fibers of 
the internal capsule which pass posteriorly to its knee (Fig. 
39) can suffer destruction or pressure if we expect to meet 
with negative results. Abscesses of immense size have been 
found in the anterior part of the frontal Ipbe without any 
sensory or motor paralysis during life to indicate the exist- 
ence of such a lesion. Tumors, softenings, and the most 
severe types of traumatism have likewise occurred without 
creating serious effects. 

In the case of occipital and temporo-sphenoidal lobes, 
to which some of the posterior fibers of the internal capsule 
are probably distributed, sensory symptoms are commonly 
observed to follow circumscribed lesions. 

The temporal lobes seem to exert an influence upon the 
special senses of touch, smell, and hearing. The occipital 
convolutions are probably associated with vision. 

An apparent connection of the optic and auditory func- 
tions with the cerebellum and optic thalamus has been men- 
tioned in previous lectures. The bearing of morbid phenom- 
ena of these special senses upon diagnosis will be considered 
in detail in a subsequent section of this work. 

In closing this important subject, let me suggest that it is 
by no means certain that lesions, which primarily affect the 
constricted portion of the internal capsule, may not, in them- 
selves, create sufficient pressure upon the corpus striatum and 
the optic thalamus to cause interference with the free action 
of some of the special centers which are believed to exist 
within those bodies. If this be the case, many of the inter- 
esting phenomena described during our discussion of lesions 
of the optic thalamus, would co-exist with those symptoms 
of disease within the internal capsule already mentioned. 
Ritti's views respecting the relations of the optic thalamus to 
hallucinations, and those of Luys pertaining to its olfactory, 
optic, and acoustic functions, have a special interest in this 
connection. 



172 



THE BRAIN. 



THE CORPORA QUADRIGEMINA, 

WITH BEMARK8 CONCERNING THE DIAGNOSIS AITD IjOCAtlUT 
OF LESIONS AFFECTING SIGHT.' 

The aqueduct of Sylvius {iter e terfio ad qfi^aium 
tTicuhivi) is covered on its superior and dorsal aspect by 1 
pairs of rounded eminences (Pig. 38), maiiiiy compoiieiil 
gray matter, called the corpora or tubercula qiiadrii 
(the so-called ''nates-' and ""' testes cerebri ^^). A 
groove separates these parts. Anteriorly, a transvers** 
prominence (the posterior commissure) limits this 
(Fig. 37) ; behind, it is continuous vtith the velnm by mem^ 
of a small median strand of longitudinal fibers, called llr 
frenulum velL The pineal gland which projects backn 
and downward from the posterior wall of the third ventri^ 
overlaps the anterior portion of this groove, resting betf 
the two upper quadrigemiual bodies (the nates). In fis 
reptiles, and birds, the quadi'igeminal bodies are two in nfi 
ber, and are called Xhe optic lobes. They are also lioUow] 
these species. In the human fcetns they are developed 
and form a large part of the cerebral mass. 

The anterior tubercles are darker in color and less pr 
nent than the posterior. Latemlly, each tubercle is proloi 
upward and forward into a prominent strand of w hjle 
stance, the brachium or arm of the corresponding tubercle.] 

The brachia are to be reganled as fasciculi sent to 
tubercle from the cortex cerebri by means of the co? 
radiata. They may also be considered as affording a eo^ 
munication with the optic thalamua The upper or an/eri 
brachium passes between the inner geniculate body and tl 
posterior extremity of the optic thalamus, or the jnilrlm 
where it may be demonstrated to join one of the roots of tlie 
optic tract, of which it ideally is a coutinuation. This is moft 
apparent in some animals than in man. The loiter or />o#- 

' In connection with the dcscii|Uioa of the gangtm of the " tegifientum crant,* 
bodies nrv conjiltlcnxl from Ibc t tantlpoibt of ibeir other pbjaiologiciil f uncdoiis. 



THE CORPORA QUADRIGEMINA. 178 

ieriar hrachivm loses itself nndemeath the inner geniculate 

body, which is situated at the side of the upper end of the 

cms cerebri. 

^ The superior quad/rigeminal bodies^ or nates cerebri^ are 

covered externally with a thin layer of nerve fibers, called the 

f ** stratum zonaXe.^^ This constitutes the only place in the 

^ farain where fibers of the first projection system of Meynert 

f (p. 81) are exi)osed to view npon its exterior. Beneath this 

sk may be seen a layer of gray matter, called the " stratum cine- 

I rewm^ which is thicker at the prominent part of the tuber- 

3 de than at its margins, and which contains numerous nerve 

^ cells of small size. Beneath this, again, lies a layer of nerve 

^ fibers which are arranged in longitudinal bundles, the so- 

^ called ^^ stratum opticum.^^ These fibers are continuous with 

I the upper brachium and the optic tract. Scattered nerve 

^ cells are found between the bundles of which it is composed. 

^ Finally, between the stratum opticum and the gray matter 

which surrounds the aqueduct of Sylvius, a layer of nerve 

J fibers, derived from the upper fillet or stratum lemnisciy may 

I be demonstrated. This layer is thickest at the margins of 

, the tubercle and thinnest at the median line, where its fibers 

appear to decussate. This gradual thinning is to be explained 

by the 'paj^age of some of its fibers to the optic layer, and 

some to the gray matter surrounding the aqueduct of Sylvius 

CPartuferi).* 

The inferior quadrigeminal bod^ies^ or the testes cerebri^ 
are comjwsed almost entirely of gray matter formed of numer- 
ous small and some large nerve cells. A thin layer of the fillet 
separates the gray nucleus of this body from the gray matter 
soriDunding the aqueduct of Sylvius. A connecting band of 

' Fledirig has shown (in some late researches made by him in reference to the period 
of defdopment of the more important nenre tracts of the brain) that the cortical layer 
of the mUeri^HT wrpiu qmadrigeminum is more intimately connected with the optic nerve 
flbtn tiMUi is the white matter of that body. This observer discards the interna! genicu- 
hto bodiet aixl the posterior corpora qoadrigcmina from the optic apparatus — a view that 
it appaffently mpported by Oiidden*s method i>f research. In the section of this work 
devoted to the special oonsideration of the cranial nerves, the optic fibers will be further 
of the kter discoveries of Guddeo and Ganser will then be men- 



14 



174 



THE BR Aim 



gray matter unites the gray nuclei of the tiro bodies, 
verse fibei*8 of the fillet bound this gray commissar 
both superficially and deeply. Those lying superfieii 
continuous, in pait, with the brachium of the luner qn 
geminal body^ and in part, also, with the fibers of the h 
fillet ; the fibers of the lower fillet are described by Me 
as being continuous with the brachium of the opposJIei 
If this continuity really exists, the commiiuication is pr 
an indirect one by means of interposed nerve cells in ihe j 
matter. 

The posterior commissure of the third ventricle, whil 
lies above the upper end of the aqueduct of Sylvias^ seemdl 
be a direct continuation of the commissural fibers of the i 
which have been mentioned. It apparently springs from tllT 
tegmentum, and, after decussating, appears to traveraa 
substance of the thalamus, and then to radiate in the wl 
substance of the hemisphere of the cerebrum, A few of 1 
fibei*s are connected with the pineal gland ; some also pfut^ 
ably act as commissuml fibers between the thalami (Fig. ST). 

This hasty and somewhat imperfect rSsume of the n w^ 
my of these bodies will enable us to intelligently ooi 
some of the views which have been advanced respecting i 
probable fimctions, and the effects of lesions within thi 
substance. 

Fwnctians of the Corpora Quadrigemina, — Among the I 
vestigators who have devoted special attention to these be 
Adamuck, Knoll, Budge, Hensen, Voelkers, Flourens^ Sel 
Ferrier, McKendrick, Gudden, and many others of note, may 
be prominently mentioned- Some have observed the efTeett, 
of their removal in animals ; others have studied the peeij 
of stimulation of their superficial and deep parts ; wliile a h 
have recorded the results of destruction of the optic appanititf 
and certain convolutions of the cerebral hemispheres, as poe- 
sessing a peculiar bearing upon points in dispute regardtlfg 
these bodies. From these different sources a mass of evidence 
has been accumulated which appears in some instances to 
lead to contradictory conclusions. It is only by com] 




FUNCTIONS OF CORPORA QUADRIOEMINA. 175 

the views of the investigators mentioned, and bringing to bear 
iiI>on the subject what is also taught us by anatomical re- 
searchy that the web may be partially disentangled. This 
subject will be considered again in connection with the fibers 
of the tegmentum cruris which are associated with these 
bodies. 

The connection of the anterior quadrigeminal bodies, or 
the nates cerebri^ with the optic tract and the sense of sight 
api)ears to be far more intimate than that of the posterior 
lobules, or testes cerebri, as was first x)ointed out clearly by 
Gndden. This observer found that the extirpation of the eye 
on one side of a young animal was followed by a degenera- 
tion and atrophy of the natis cerebri and its brachium ; the 
testis and its brachium remaining unaltered. This view is 
apparently sustained also by the fact that the mole has the 
testes cerebri largely developed, whereas the nates cerebri are 
markedly atrophied. Adamuck believed that he had clearly 
demonstrated the existence of a center within the nates which 
presided over those movements of the eye and pupil which 
are essential to the accommodation of vision for near ob- 
jects j as well as the coordination of all ocular movements. 
KnoU found, however, that reflex contractions of the pupil 
remained after removal of the corpora quadrigemina ; and 
Hensen and Yoelkers have been apparently successful in 
mapping out the topography of the centers which preside 
over ocular and pupillary movements with greater accuracy 
than their predecessors. They were able to produce at will, by 
carefully applied electric stimulation in the region of the floor 
of the aqueduct of Sylvius, independent movements of the 
eye and pupil. In the dog, upon which animal these experi- 
ments were made, a center which governed the accommodor 
tion of vision^ was found to be situated in the posterior part 
of the third ventricle near to the aqueduct, while a center for 
pupillary contraction and one also for its dilatation were found 
in the front part of the floor of the aqueduct of Sylvius, the 

' Thb oent«r manif efted an H>pAreDt oootrol over the eiliary miud$ onl j, and created 
I la tiM antero-poaterlor measorement of the cryitallino lem of the eye. 



176 



THE BRAIN. 



former lying in the median plane and the latter more to d( I 
sides. The same observers state that a center, iv^hich giiitfli| 
those muscles of the eyeball which are sujjplied by th« tiB't 
cramtil nerve, can be found in the floor of the aqoedact^B 
mediately behind that which presides over pupillary coowj 
tion. Whether we accept these statements as democ 
or not, we know positively that such centers exist somei 
and are so associated in their action that, when the ej 
are directed inward and downward, as for near visioiw 
pupils are at the same time contracted ; and when the > 
balls are directed upward and returned to a state of paal I 
lelism, the pupUs are dUated to a corresponding extenL Oil 
the contrary, when the eyeballs are moved sidewap il | 
unison, the pupils remain unchanged. A most positiTe prat I 
that the pupillary movements are not of a psychical natmei^ 
afforded by the experiments of Adamuck, who prodneBl 
movements of both eyes by stimulation of the corpora quadii- 
gemina of either side, and who also obsen^ed that the po{lb ' 
were at the same time made to perform their proper mew 
meats. When, however, the corjinm quadrigemina of tk 
two sides were separated by a median incision^ stimiilatio<tt d 
the centers of either side caused movements of the ooci^ 
sponding eyeball only. In both experiments, changing tk 
seat of stimulation caused modifications of ocuiar moiw 
ments. 

It was only after Knoll had shown that the reflex mai^ 
ments of the pupils remained after complete excision d 
the corpora quadrigemina^ and the discovery of Hensen usA 
Voelkers that the effects of stimulation of these bodies, •» 
fli-st practiced by Adamuck, were not uniform until the im^ 
d^lying parts were directly reached, that discrepancies bfr 
tween these observers were explained. 

To determine the true mkitions which these Ixnlies be^r to 
the special sense of sight is perhaps one of the most diffiralt 
problems in physiology, 

Flourens and many subsequent observers have shown o« 
that unilateral extirpation of the corpora quadrigemina in 



^Ata 



FUNCTIONS OF CORPORA QUADRIQEMINA. 177 

mammals and birds leads to a blindness of the opposite eye ; 

c and even when the cerebral hemispheres are removed without 

^ disturbing these bodies, that an apparently crude vision still 

£ xemains. We have many exi)eriments, however, to show that 

^ destruction of certain convolutions of the cerebrum also pro- 

^ dnced the most profound effects upon vision in spite of the 

, undisturbed action of the quadrigeminal bodies. When we 

, discussed the optic thalamus, it was also stated that many 

, clinical observations pointed toward the existence of a center 

within that body which in some way modified or presided 

over visual impressions. We know also that lesions within 

the so-called '* internal capsule" of the cerebrum frequently 

produced most serious impairment of vision, and conjugate 

deviation of the eyes. 

In the pages which treat of the ganglia of the tegmentum, 
other functions of the corpora quadrigemina will be dis- 
cussed. The reader is referred, therefore, to them for more 
exhaustive information. 

Now, how are we to explain, theoretically, such contra- 
dictory phenomena ? What views are we apparently justified 
in holding (from the standpoint of our present knowledge 
wpon the subject) regarding the relations of the cerebral 
cortex, corpora quadrigemina, corpora geniculata, optic 
thalami, and internal capsule of the cerebrum, to the fibers of 
the optic tracts and the external organs of sight) 

I think we are justified in attributing to the cells of the 
cerebral cortex (the external gray matter of the hemispheres) 
our conceptions of the external world, as portrayed to us by 
means of the sensory nerves and the special senses. No mat- 
ter how many collections of gray matter may be interposed 
along the course of the nerve fibers which convey these im- 
piesfldons to the cortex (each of which may possibly help to 
modify them), there is no argument which has yet been ad- 
vanced which tends to overthrow this general law. Every 
image cast upon the retina, every sound-wave which enters 
the external ear, every odoriferous particle which reaches the 
noee or is placed upon the tongue, every manner of form by 



179 



TEE BUAi:i\ 



which we are brought into direct or indirect FolatioQ 
surrounding objects during life, becomes a conscious imf 
sion only by affecting in some unknown way the cells of 1 
cerebral cortex. Here the image thrown upon tlie n^tiiml 
comes to our mind the pictui'e actually seen ; the soimd-i 
becomes the musical note; the contact of the odorifercc 
particle is transformed by the brain cells found in its eaEle 
gray matter into a sense of smell or of taste ; objects 
recognized as smooth or rough, hard or soft, heavy or lig 
only when these silent workers become thrown into acti^ill 
by some sensoiy impulse carried to the convolutions of 
brain by means of nerve fibers. 

We have reason to believe that the fibers of the 
nerve reach the gmy matter of the convolutions of the 
brum by different routes ; and that each bundle meeUn (g 
where in its course) an interrupting mass of gray matrer, 
the cells of which the nerve fibers become associated, aad 
from which cells they are subsequently prolonged to thuoe d 
the cortex. This is the common method of arrang^i 
all nerve libers, after they enter the substance of the bi 
spinal cord, to which the optic fibers are no exceptian. Tfce 
interrupting cells of the optic fibers are comprised chielj 
within the optic thalami, the corpora geniculata, and the 
corpora quadrigemina. Stilling believes that a bundle of 
fibers can be traced to the corpus subthalamicum.^ ftod 
another to the medulla oblongata. The so-caUed ^^ftMctf 
optic ganglion of Meynert'' is thought by some to be abo 
connected with a slender fascicuhis of the nerve. 

When speaking of these interpolated masses of gray 
ter and their controlling action upon all impulses sent lo 
brain, Michael Foster makes use of the following wor 
which I quote on account of their applicability to the stibjc 
under considemtion : 

^' All day long and every day, multitudinous afferent 
pulses from eye, and ear, and skin, and muscle^ and otbi 
tissues and organs, ai^ streaming into our nervous systeml 
and did each afferent impulse issue as its coiTehirive offer 



FUNCTIONS OF CORPORA QUADRIOEMINA. 179 

motor impulse, our life would be a prolonged convulsion. As 
it is, by the checks and counter-checks of cerebral and spinal 
activities, all these impulses are drilled and marshaled and 
kept in orderly array till a movement is called for ; and thus 
we are able to execute at will the most complex bodily ma- 
noeuvres, knowing only why^ and unconscious or but dimly 
conscious how^ we carry them out.'' 

The study of the course of the individual fibers of the 
optic nerve in the region of the optic chiasm (Fig. 41) is 
rendered particularly difficult by the curved direction which 
they take ; hence the relative proportion of the longitudinal 
and decussating bundles is still a subject of dispute among 
authorities upon that subject. Stilling states that inter- 
retinal fibers, which have no cerebral connection, can be 
demonstrated, while other authors deny it. Some assert that 
all of the fibers, which are prolonged into the optic tract, 
decussate in man, as they are known to do in the lower verte- 
brates and some mammals, but pathological observation tends 
to confute this view. Charcot advanced the theory some 
years since that those fibers of the optic nerve which do not 
decussate at the chiasm are continued along the optic tract of 
the corresponding side and eventually decussate (probably 
within the substance of the corpora quadrigemina) after 
which they are continued into the internal capsule of the op- 
posite hemisphere. He sustained this theory on pathological 
grounds. 

The latest researches of Wernicke and Stilling respecting 
the anatomy of the brain have tended, however, to confirm 
the original view of Meynert that the optic fibers radiate into 
the occipital lobes, as well as that of Munk also, who first 
advanced the statement that the area of the brain function- 
ally associated with conscious visual impressions was confined 
to the cortex of the occipital lobes. 

Wernicke has shown conclusively that a tract of fibers 
passes from the pulvinar of the optic thalamus to the occipital 
lobe of the same hemisphere, and that this tract is continuous 
with the fibers that compose the optic tract. He demon- 



THE BiCJjy. 



L 



strates f urtheimore that this tract passes heneaih (he an^lm 
gyrus, Ferrier and Dalton have both pronounced the tismI 
area of the cortex to be confined exclusively to the^e angnbr 
eonvolutions of the parietal lobe. This discovery of Wtfrmi^ 
seems to be a means of reconciling the views ol Ferris ill 
Munk, that have been directly opposed to each other ; wm 
it is evident that a deep injury to the angular gyrus woqU 
cause impai lament of Wernicke's tract (see Fig, 43). 

A very valuable reswmi of the latest discoveries, respect^ 
ing the visual area of the cerebral cortex iu man, by m 
of pathological investigation, has been lately publi-^ 
M, Allen Starr,' of this city. This author brings . 
the results of autopsies made upon some thirty cases 
brain lesions had produced hemianopsia during life, 
draws conclusions from these cases that differ from 
that have been accepted as proved until within the past fire 
years. Some of the more important deductions dran-n (tm 
this remarkable compilation of autopsies are as follows ; 

1. The supposed decussation of those optic fillers, whidf 
do not cross at the chiasm, witliin the corpora quadr^emiBi 
(as schematically represented by Chai*cot in his diagram^ and 
taught by him for years post), is erroneous, and haa latelf 
been discarded by its author. 

2. The diagram of Grafe and P6r6 meets with the anthaf^ 
approval ; and it has been adopted by Charcot, as more o<if> 
rect than his own. 

3. He sustains the opinion of Mauthner that ** there 
well-authenticated case in which a lesion of one hernia 
has produced blindness of the opposite side." 

4- He believes chat many of the cases, reported as Ihooe of 
amblyopia from brain lesions, are capable of being shown to 
be affected with hemianopsia, 

5. That any lesion of the brain, If it affects the liben 
the optic tract, the pulvinar, Wernicke's tract, or the 
of the occipital lobe, will cause hemianopsia, Hemiano 
must therefore be regarded as a symptom of a circumscribed 



^j^m^^ 



ML 




HEMIANOPSIA FROM BRAIII-LE8I0N8. 181 

lesion of one hemisphere rather than a general symptom of 
brain disease (see Fig. 43). 

6. That the older view that '* lateral homonymous hemi- 
anopsia" is always due to a lesion affecting the optic tracts 
at the base of the brain is an error and unworthy of j)er- 
petuation. 

7. That the view of Munk, who believes that each occipi- 
tal lobe presides over the vision of the corresponding half 
of each eye (the left lobe over the left half, and the right 
over the right half of each eye), is correct. The view of Per- 
rier, that the angular gyrus is directly associated with the 
visual sense, is not thus far supported by pathological re- 
searoh in man. 

It is known that destruction of the retina in the dog gives 
rise to a degeneration of nerve strands in both optic tracts. 
The chiasm of the cat has been divided T^ithout destroying 
vision, thus warranting the inference that the decussation at 
that point is incomplete. All the experiments that have been 
made to determine the relation of the cortex cerebri to vision 
are in favor of an incomplete decussation, because the sight 
of both eyes has been impaired by unilateral lesions. A 
laige number of cases have been rei)orted where lesions 
affecting one optic tract have produced hemianopsia of both 
retinffi. 

Possibly the corpora quadrigemina preside over other 
functions in addition to the special sense of sight.' Flourens 
was the first to notice that injuries of the corpora quadri- 
gemina^ of one side produced peculiar phenomena called 
^^forced moveTnerUSy^^ and that the complete removal of 
these bodies caused inco-ordination of movement. These 
exi)eriments have been repeatedly verified. In the frog, 
the removal of the optic lobes causes an almost entire 
loss of the power of co-ordination of movemerUs required to 
preserve its balance; but it can still perform a variety of 
movements where co-ordination is demanded, such as swim- 

* The inferior corpora quadrigemina do not appear to be directlj associated with optio 
(Fladifig and Gudden). 



THE BBAIS, 



ming, leaping, etc. Schiff has attributed these effects^ 
ever, to injury of deeper pirts (crura cerebri). We Bt 
discuss phenomena which are somewhat similar whea 
cerebellum is under discussion ; but we have as yet no 
tive knowledge of the physiological connections between 
optic lobes and the cerebellum. 

The sense of sight has a marked effect upon co-ordfa 
of movement, as we all know. Dizziness often follows 
close inspection of a water-fall, or the rapid flight of abj 
beftJi'e the eyes. The effect of extreme elevation from 
rounding objects frequently produces marked dii^turbonees* 
equilibrium. These facts seem to sustain the belief thiil t)» 
optic fibers must be closely associated with the oerebellum, 
pons Varolii, or crura, and the discovery of Ploorens is M 
additional argument in its favor. 

Finally, it is believed by some that a center which presidei 
over the secretion of sweat is situated somewhere in the re^ofi 
of the corpora quadrigemina. 

A 8UMMABT OF THE EFFECTS OF LESIOITS OF THE OPTIO 
AJTD OPTIC NERVES. 

In connection with the discussion of the corpora qua 
gemina and the probable course and distribution of tl 
nerves of sight, it seems to me an appropriate time to mentic 
some interesting phenomena pertaining to vision which 
an important bearing upon the localization of intra-cnutial 
lesions. Before doing so, however, it will be necessary I^Mi 
hastily review a few important facts which are essential to «™ 
complete understanding of the subject. 

The optic apparatus may be said to comprise the fallow- 
ing parts : 

1. Certain cortical centers, which act as the interpreter^ 
of visual sensations transmitted to the convolutions by means] 
of the nerve fibers wdthin the white substance of the cerebr 
hemispheres. These centers probably transform all impulses^ 
(which start originally as retinal impi-essions) into eofi^cioui 
viru/il perceptions. 





GANGLIA OF THE OPTIC APPABATU8. 183 

2. Nodal masses of gray matter^ with which the optic 
nerve fibers are intimately associated before entering the 
white substance of the cerebral hemisphere. These masses 
include the corpora quadrigemina, the corpora geniculata, 
the corpus sub-thalamicum, the optic center of the thalamus 
(Luys), the basal optic ganglion (Meynert), and probably 
some centers situated within the medulla oblongata. 

These interrupting ganglia probably exercise a modifying 
infiuence of some kind upon the impulses which are con- 
ducted to them from the retinse ; and subsequently allow 
them to pass to the cells of the cerebral convolutions so 
altered or maierialized as to be readily transformed into 
conscious perceptions of external objects recognized by the 
eyes. It is not known what the special function of each of 
these interrupting masses is, nor can it be determined except 
through a more complete knowledge of cerebral architecture 
and pathology than we now possess. 

3. Nerve fibers within the optic nerves and the optic 
tracts — the latter being the prolongation of the former behind 
the chiasm (see Fig. 43). These fibers convey all impressions 
made by objects external to the body upon the retinae, by 
means of the organ of sight, to the interrupting masses of 
gray matter mentioned above. The waves of light, which 
enter the pupil and fall upon the retina, create in the struct- 
ural elements of that membrane (probably in the so-called 
** rods'* and " cones of Jacob") impulses which are conveyed 
by means of the optic fibers to the interrupting ganglion cells, 
and then to the convolutions of the cerebral hemisphere 
where these impulses become sight-impressions. It is evi- 
dent, therefore, that anything which tends to interfere with 
the perfect conducting power of these fibers will impair the 
power of accurate conception of external objects revealed to 
us by means of vision, because the cortical centers are cut off 
from their retinal connections ; hence the study of the course 
of the nerve fibers and the relations of the ner\'e tracts to sur- 
rounding parts becomes of vital importance to the advanced 
neniologiat (the diagnosis of many cerebral and intercranial 



THE BRAIK 




lesions resting entirely or in part upon optic pi 
which are to be interpreted from an anatomical standi 
alone). 

4. The retina^ and its various structurid elements. Tto 
membmne constitutes the peripheral portion of the nerro^w 
optic apparatus. It is the only place in the body where tk 
nervous system is so exposed as to admit of a direct examitt- 
tion, since we can see it by aid of the ophthalmoscope, sol 
thus study its diseased conditions as well as its appearaooe in 
health. Physiologically, it is to be considered as the i* 
sitive plate from which the details of outline and color dt 
external objects are telegraphed to the convolutions oC 
cerebrum. 

The experiments of Flourens, already quoted, first d^ 
strated that a crude sense ofvisioji remains in animala wl 
have been deprived of their cerebral convolutions above the 
level of the corpora quadrigemina, and many subseqQ^t 
observers have attested to the accuracy of his conclusioE 
These experiments point to some functions within the 
of gray matter that are associated with the optic fibers, 
bear a close analogy to those of the cortical cells of the so- 
called ** visual area'' of the hemisj^heres* We are forced to 
accept the view that these ganglionic masses take cognizanne 
of visual impulses in an imperfect way, although the cerebral 
convolutions seem to be essential to a complete transfonna- 
tion of visual impulses into conscious sight-perceptions* Sec^ 
tion of the optic fibers after they leave the brain invariably 
destroys sight, thus proving that the retina itself has no ii 
herent power of interpreting visual impressions which are < 
upon it. 

Now, from what has been stated, we can classify leaion 
which may aflfect or destroy the visual function as follows : 

1, Lesions qf the retina^ or of some of the other stnic 
nres of the visual apparatus which prevent the formation < 
images within it. 

2. Lesions of Ike optic nerve^ anteriorly to the chw 
which point the decussating fibers have crossed each other. 



seqa^t 
lusioa9|H| 



INTRA-CRANIAL LESIONS AFFECTING SIGHT. 



186 



3. Lesions of the optic tracts and the chiasm, or of parts 
80 adjacent to them as to create pressure ux)on the optic 
fibers. 

4. Lesions of those ganglionic masses whose connection 
with the optic fibers has been demonstrated by anatomical or 
pathological research. 

5. LesioTis of certain regions of the cortex cerebri, which 
have been shown to be in intimate association with vision. 




Ffto. 41. — A diagram designed by the author to show some of the relations of the optic 
and iAfcutory nerve fibers to surrounding parts, 

F, frontal lobes of cerebrum ; P, parietal lobe ; T, temporo-sphenoidal lobe ; S, fissure of 
SyWiuB ; R, fissure of Rolando ; 0, occipital lobe ; C, cerebellum ; M, medulla ob- 
longata : 1, olfactory nerve ; 2, optic chiasm ; 3, motor-oculi nerre ; 4, corpora quad- 
rigemina ; 6, trigeminus nerve ; a, basis cruris ; 6, tegmentum cruris. The diamonds 
in the occipital lobe, the eortieal tnsual centers of Munk. The cerebellum and pons 
Varolii are shown as if separated from the cerebrum, in order to make the relations 
of the crufl to the optic tracts apparent. This diagram should be compared with 
Fig. 48 to make its bearings upon cerebral localization apparent. 

6. Lesions of the internal capsule of the cerebrum ; or of 
such parts of the medullary center of each hemisphere as con- 
tain fibers connected with the ''visual area " of the cortex. 

The first set of causes of impairment of vision enumer- 
ated above belongs properly to the province of the oculist 



TEE BEJIX, 



rather than of the neDrologLst, althongli there is one 
dition which should always be sought for when cei 
disease is suspected, viz., neurO'TetinitiSj or tiie 
^^ choked disJc.^ The evidences of this condition are affonli 
by the ophthalmoscope alone, because vision is not im 
in the early stages. Its existence is recognized eiirly by 
tuosity of the veins of the fundus of the ej^e, swelling of 
optic nerve, and obscureness of the margin of the disk ; hti 
the outline of the disk becomes unnaturally shari> and 
tinct, the nerve atrophies, the vessels become very small, itf 
fundus is unnaturally pale, and vision is impaired. This con- 
dition is always (!) bilateral, although it is not uncommoo to 
note a marked diflference in the severity of the change iB 
the two eyes. Special attention is called to this disease of 
the eye, because it is now considered as one of the most r^Ii 
able signs of conditions of the cerebrum which tend to pD>^ 
duce a graduaUy increasing pressure^ particularly of Ittmon: 
and, in the second place, because its existence is liable to be 
overlooked, since vision is not impaired early. 

The various phenomena which are due to paresis of 
lar muscles,' and which have often the most positive value 
definitely localising cerebral disease, can not be considei 
under this set of symptoms or in this connection, bec^n 
they do not govern in any way the sense of sight, alt bo 
they assist the eye to focus images of objects upon the retina. 
My friend Dr, W, C. Ayers has lately made a valuable ooo- 
tribution to medical literature in the form of a brochure upon 
the value of the ophthalmoscope as an aid in general diagm 
sis,' which may well be consulted by all who desire practi 
information in regard to the utility of this instrument, 
the intimate relationship which exists between the eye 
the body, as revealed by clinical study. 

The second set of causes of impairment of vision (lesions 
of the optic nerve anteriorly to the chiasm) includes chiefly 



IpOD 

ticofl 

an(H| 



■ These will be fmrad bj oonsKiltiivg iubfeqtie&t p«g«i wbjch relmte to Ur 
octtH netre. 

* ** AmeHoui Jaumal of the Medkml SdMMOi,** Ootobcr, 1883. 




CEREBRAL LESI0K8 AFFECTING 8I0HT. 187 

those conditions within the orbit which create pressure 
upon, or destruction of, the optic nerve after it leaves the 
cavity of the cranium. It is evident from the diagram (Fig. 
43) that the impairment of sight in this case will be confined 
exclusively to one eye. The phenomena produced by disease 
within the cavity of the orbit upon sight must, of course, 
depend upon the amount of injury done to the optic nerve. 
Blindness of one eye indicates, as a rule, some exciting cause 
outside of the cavity of the cranium. Remember that neither 
true amblyopia or total blindness of one eye occur in con- 
nection with pressure upon the optic nerve fibers either at 
the chiasm or behind it. 

We come now to the third set of causes enumerated on 
I)age 184, viz., lesions of the optic tracts and chiasm. This 
set includes not only actual lesions of the nerve, but also 
pressure-effects exerted upon the optic fibers by lesions of 
adjacent structures. Before we pass to the consideration of 
the diagnostic symptoms of this condition, it is important 
that we review some of the relations of the optic chiasm and 
the optic tracts. 

If we trace the optic nerve fibers from behind forward, we 
find that the optic tracts appear to arise from the optic thai- 
ami, the superior quadrigeminal bodies, and the corpora ge- 
niculata. As they leave the under surface of the thalami, they 
make a sudden bend forward and curve around the crura 
cerebri in the form of a fiattened band (Fig. 43). At their 
anterior i)ortions the tracts become closely attached to the 
croia, and, in the region of the tuber cinerium, an accession 
of fibers to the tracts may be demonstrated. Before the 
chiasm is reached the tracts become more cylindrical in 
form. 

The optic commissure^ or chiasm^ is about half an inch 
long in its transverse measurement, and lies upon the olivary 
process of the sphenoid bone. The internal carotid arteries 
lie in close relation with it at the sides, and the anterior cere- 
bral arteries, with their communicating branch, are so dis- 
IKMBed as to constitute what might be called a loop about the 



188 



THE BUAIN. 



optic nerves. The clinical bearing of this fact will be ' 
oussed later. Henle reports a few remarkable instances wh 
the chiasm was wanting, the optic tracts being coudnu 
without interruption to the eyebaUof the correapondlDgfi 
but these abnonnalities are so rare as to be of no pr 
importance from a clinical standpoint. 

We are now able to study the diagram wliich I draw i 
the blackboard, and to properly interpret the clinical 
tions which may be drawn from it* It is intended to jwr 
the effects of localized pressure upon the optic chiasm 
optic tmcts, as well as those of destructive lesions of the i 
and of the ''internal capside" of the brain. 

Now, tbis diagram is designed chiefly fco portray 
mechanism of one peculiar symptom, and the use to whkllir 
may be employed by the neurologist in definitely det 
the seat of the disease-lesion wliich is creating it* I refer I 
** heviianopsiay^ or blindness of one lateral ha^qft/se rHin^ 
The term '* hemiopia" is often employed to express the saw 
condition, although it is to my mind a poor one, since it ^m^ 
ply means *'half vision," and thus faUs to express the, 
intended. 

The following steps are commonly employed to detect 
existence of thi3 symptom ; Request the i>atient to close i 
eye by pressing the lid down with the finger, and to so dine^ 
the oi>en eye as to concentrate its gaze upon some fixed obJ€ 
near to it. [I usually hold up the foi'efinger of my own 
within a foot of the patient's open eye, and tell him to Ic 
steadily at it] Having done this, take some object which j 
easily seen (such as a small piece of white paper) in the imei 
ployed hand, and move it to the right and left of the obJ€ 
upon which the patient is gazing, and also above and belof 
the object, asking the patient, in each case, if the two objects 
are seen simultaneously and with distinctness, and notice upon 
which side of the fixed object the patient can not jierceive the 
moving object It is self-evident that the retina is blind upon 
the side opposite to that upon which the moving object is lost 

' Thlf sTtoptom will be discttssed verj i^xWy in the teoond eedlon of Uila < 




CEREBRAL LESTONS AFFEOTINO SIGHT. 



189 



A // 

sBf ■ ■ — -^f/ // Space flllod bf tli« CTUom 

* /j // wr^tui, around which ^» 




^B^peHo^ oorpns 
oitwiriir«mlxiiu. or 
tne "^iMilflDsr. 



I Biffbt tnet of 
1 wcnitcke. 



Tlniia Mni of cor- 
tex or Hiftti oerebnl 



Fta. 4S.— il diagram detigned by the aulhor to iliwirate the latett viewt in reference 
to the eouree of the optic nerve fihere, 

Th* dotted lines (A and B) arise from the left hen)i»pliere ; the continuouR lines (C and D) 
trise from the right hemisphere. It will be perceived that the occipital cortex of 
the left bemisphere is shown to be connected with the left half of each eye, and the 
rtefat beniaphere with the right half of each eye. The dia<:^m also nhows that the 
flbtrt of each optic tract pass through the external geniculate body, the sui>erior 
corpora qnadrlgemina, or tlie pulvinar of the thnlamus, heforc they rudiate to the 
ooct|rft«l ooitex; 1* 2, 8, 4, 6, indicate the Tarious localities where lateral homony- 
moos bcmlmn<^>ala can be produced ; C, G, E, the external geniculate body ; C\ 0, I, 
ialortuU genleiibite body. 

15 



190 



THE BRAl.W 



to sight. The visual area can also be accurately drawn 
means of a i)eiimeter if it is deemed advisable. 

The most common form of hemianopsia is tliat in w! 
the nasal half of one eye and the temparal half of the 
is blind, tliis condition being the result of injury dooa 
parts posterior to the chiasm. When the chiasm is aA 
we commonly meet the bi -nasal type* 

There is still one more form which is occasionally en< 
ered, viz., the bi-temporal type. This has been int 
by an autopsy made npon a case intrusted to the care of 
Prof. H. Knapp, of this city. It must be evident that tk 
chances would be extremely smoU of ever encountering a bi- 
lateral lesion which would affect only those fibers of the optii 
chiasm, or optic tract, which supply the temporal half of eacli 
retina, and at the same time leave the decussating fibers in- 
tact. Huw, then, ai'e we to account for the fact that this torn 
is sometimes met with? In the preceding portion of tik 
lecture I called your attention to a peculiar arran^eraeat 
the arteries in the region of the optic chiasm, Now^ it hsS^ 
been shown that atheromatous degeneration of the ** circle of 
Willis " (a peculiar arrangement of blood-vessels at the baat 
of the brain) so impairs the elasticity of the arteries as 
cause the pulsations of the carotids to aid in creating a 
of injury to the chiasm, so limited in its extent as to im 
only the fibers distributed to the temporal halves of 
retinfe, and thus to create bi-tempoml hemianopsia. 

We may, therefore, summarize the clinical signifi 
this peculiar form of blindness as follows : 

(a) The lateral homonymous varietp (where the left or 
right half of each eye is simultiineously affected) indicniei 
lesions affecting the optic tract or its prolongations Ihro 
the brain-substance to the cortex of the occipitiil lobes (t 
cortical centers of Munk), 

(6) The bi-nasal 7>ariefp indicates a lesion pressing upon 
the central portion of the chiasm. 

(c) Tlie hl'iemporal rariefj/ indicates, as a rule, athemmi 
tons degeneration of the circle of Willis, Possibly (> i sy 



CEREBRAL LESIONS AFFECTING SIGHT. 191 

metrical lesions of the outer part of the chiasm might also 
cause it. The view of Charcot, that a decussation of the 
optic fibers takes place within the substance of the corpora 
qoadrigemina, is not sustained by a recorded case of bi-tem- 
poral hemianopsia produced by a circumscribed lesion within 
those bodies, and can be dismissed as incorrect. 

{d) Finally, lesions of the internal capsule are sometimes 
associated with lateral Jiomonymous hemianopsia. 

The bi-nasal, and also the bi- temporal, varieties are due (as 
a rule, at least) to lesions confined to the anterior fossa of 
the cranium ; hence we sometimes find the olfoAstory nerve of 
the side corresponding to the seat of the lesion simultaneously 
afFected, and creating anosmia (loss of smell) with or without 
subjective odors. 

If the lesion be situated within the middle fossa of the 
cranium, the optic trax^ts may be affected, thus causing lateral 
homonymous hemianopsia, while the motor nerves of the eye 
may be simultaneously pressed upon as they pass through 
that fossa on the way to their foramen of exit from the cra- 
nium (the sphenoidal fissure), thus producing more or less 
imx)airment of the movements of the eyeball of the same side. 
The value of these complications cannot be over-estimated, 
when they exist, because they are of the greatest aid in diag- 
nosis, and often enable a skilled anatomist to positively deter- 
mine the seat of the lesion. 

The fourth set of causes of impairment of vision (according 
to the classification given on page 184) comprises all diseased 
conditions which are limited exclusively to those ganglionic 
masses through which the optic fibers pass in order to reach 
their connections with the convolutions of the cerebrum. If 
we confine ourselves to this strict limitation, we are forced to 
admit that little can positively be said respecting them which 
will bear upon intra-cranial diagnosis, because, to my knowl- 
edge, there are no recorded cases where evidences of cerebral 
disease have been confined exclusively to these regicms. 

There are some symptoms, however, that may coexist with 
disturbances of vision when lesions exist in parts contained 



TBE BRAIN. 



within the middle fossa of the skull; these may proreci] 
assistance in deciding as to the seat of the lesion. Ajbcii 
them may be eiiumemted : 1. Crossed para l//s is of the ^*fltrf I 
nerve and hody^'* type, a condition chanicteiized by haat 
plegia and paralysis of the motor-oculi nerve of the oppaigie| 
side. 2. Crossed paralysis of the '''' olfacttyry nerit adX 
body^^ type, a condition characteiized by hemiplegia and kssl 
of smell in the opposite nostril. 3, Hemiplegia, or loss of ty] 
power of voluntary motion in one lateral half of the body, ^ I 
Hemianesthesia^ or a loss of sensation in one lateral haU' 
the body. 6* Ataxir symptoms^ indicating an impalrmeiit < 
coordination of muscular muveiuents. 

The first of these points positively to a lesion qf the cru 
cerebri, if unattended by other symptoms. But, if evideoin!* 
of disturbance of the optic tract (lateral homonymous hemia- 
nopsia) exists simultaneously with this form of crossed jm* 
ralysis, it indicates that the lesion is large enough to interfei^ 
also with the optic nerve, as well as the motor-oculi fibew 
within the crus and the motor tract of the cms. The 
toms of this variety of crossed pamlyaia are ao well dc 
as to render it almost impossible to mistake them. 

The second condition (crossed paralysis of the oUaetofy 
nerve and body type) may occur when the lesion is sufficieot* 
ly large to create pressure ujiuu the motor tracts of the braiD, 
thus causing hemiplegia of the opposite side, and at the same 
time to injure the olfactory nerve, thus causing anosmia (Jo» 
of smell) in the nostril of the coiTespniidin^ side. Of course 
the optic tract or chiasm must be involved simultaneously 
when hemianopsia also exists. The tests for anosmia wU 
given in a subsequent section of this work. 

Hemiplegia may occur in connection with beniiano] 
when the lesion is of sufficient size to affect any part of 
so-called ^^ motor trnct'^- simultaneonnly \\\t\\ the optic nervel 
fibers. The motor paralysis is chiefly manifested on the eidel 
opposite to the lesion ; because the fibers of the motor tracd 
decussate at the lower part of the medulla. Flechsi^ huaA 
shown that, in rare cases, exreptions to this genei'al rule arsj 



leJH 



GROSSED PARALYSIS WITH HEMIANOPSIA. 



193 



to be explained by an abnormality in the decnssation of the 
motor fibers. Hemiplegia is now and then observed in con- 
nection with hemianopsia; although the olfactory, motor- 
ocnli, trigeminus, and facial nerve roots are equally liable to 
be simultaneously involved. This explains the mechanism of 




Fko. 44. — A diagram designed bit the author to thow the getund tumm of fbtn tfi Iht 
^9enmry^ and ^^ motor traetty** and their rdation to certain faacieuU of the optie 
tracts, (Modified from Segum.) 



S^ aenaory tract in posterior region of roeaocephalon, extending to and T, occipital and 
temporal lobes of hemispheres ; M, motor tract in basis cruris, extending to P and 
F,j9arietal and (part of^ frontal lobe^ of hemispheres; C Q, corpus quadrigeminum ; 
O T, optic thalamus ; N L, nucleus Icnticularis ; N C, nucleus caudatus ; 1, the fibers 
fbrming the ** tegmentum cruris ** (Meynert) ; 2, the fibers forming the " basis cruris *' 
(M ejnert) ; a, fibers of the optic nerve which beoome associated with the ** optic cen- 
ter ** in the optic thalamus, and arc subsequently prolonged to the ** visual area ** of 
the oonvolutions of the cerebrum ; 6, optic fibers which join the cells of the ** cor- 
pora quadrigemina,** and are then prolonged to the visual area of the cerebral cortex. 



the four varieties of *' crossed paralysis" which are encoun- 
tered, the hemiplegia being on the side opposite to the lesion, 
and the symptoms produced by paralysis of the cranial nerve 
being confined to the side corresponding to the lesion. 

ffemiancBsthesia indicates some disturbance of the nerve 
fibers of the so-called ^' sensor 7/ tract ^\' the loss of sensation 
being confined to the lateral half of the body opposite to the 
lesion which causes it, because the sensory fibers decussate in 
the spinal cord. In cerebral hemianesthesia there is more or 
less insensibility to touch, pain, and temperature, and also 



194 



THE BBAIN, 



abolition of muscular sensibility with complete retenticm 
electro-motor contnictility. The miic!ous meQibnines of 
eye, nose, and mouth ai'e also anaBsthetic, Now Ihe upi 
portion of the sensory tract lies in the i>osterior regions \A\\ 
crua cerebri and the internal napsule, and is in elode n?l 
with the posterior basal ganglia. The libera of the optic Gai 
may be likewise affected simultaneously with lesion.^ of 
foIh:»wing parts: The crus, the intenial capsule, the o 
thalamus, the corpora qiiadrigemina, the geoiciilate boditsv 
and the medulla. Our ability to definitely locate ledoiis vi 
the sensory tract, or of the ganglia connected vnth it, b « 
yet imperfect. It is only by the careful study of aasodated 
symptoms that conclusions can be arrived at. 

Ataxic manifestations^ occurring in connection with eri- 
denees of impairment of the sense of sight, open a mde 6eH I 
for speculation. The proximity and intimate structural i^ \ 
tions of the cerebellum with the corpora quadrigemina, basil , 
ganglia^ cms, and medulla, suggest the possibility of eerebe^|| 
lar lesions when these two symptoms are present to a marict'^^ 
degree. The subject is too complex for discussion here, 
will be more intelligible after the cerebellum has l?een coi 
sidered. 

The J{fth set of causes of impairment of vision previoasl 
>ulated on page 184 will now be considered. Within t\\ 
past few years the attention of physiologists has been direc 
ed, by some remarkable results of experimentation ujMin thi 
convolutions of the cerebral cortex, toward the view that 
tain convolutions of the cerebrum were essential to perf 
visual perceptions. To Flonrens and some of the older ol 
servers, who had remarked that the removal of portionjs 
the hemispheres, or serious injary to them, created blindn^ 
the loss of sight appeared to be temporary. The statemeni 
was explained in various ways, until Goltz called atteniion t 
the error of supi>osing that no permanent imperfections ol 
vision remained after extensive injuries to the cerebral hemi 
spheres. This author showed that the permanent results 
such injuries might escape notice unless special care was 



PSYCHICAL BLINDNESS. I95 

in the examinations of the animal. The i)eculiaritie8 of the 
I)ermaBent impairment of vision are manifested only when 
the animal is subjected to tests which had been invariably 
potent before the cerebral injury. Thus the dog, from which 
portions of the cerebral hemispheres had been removed, fails 
to recognize his food by sight ; when he is threatened by a 
whip he is not cowed ; he is no longer affected by objects 
which caused him to be violently excited before the mutila- 
tion ; he makes no response to the extension of the hand of 
his master for the paw ; and yet this animal can see to avoid 
objects and to perform all varieties of movement as well as in 
his natural condition. Another striking characteristic of this 
impairment of sight is, that under educational exercise recov- 
ery takes place. The dog may again be taught to fear casti- 
gation and to shrink at the sight of the whip ; to recognize 
his food ; to obey the motion of his master's hand, etc. 

Two interpretations of these phenomena have been sug- 
gested: The first is, that the animal has imperfect visual 
perceptions, so that objects appear misty or as if seen through 
a gauze. Goltz suggests that they may appear as if all the 
colors were washed out, thus depriving food, dress, etc., of 
their characteristic appearances. The second interpretation 
supposes that the memory of past visual impressions is ef- 
faced, so that the animal forgets the })ain of the lash, the taste 
of the food, the features of his master, the tricks which have 
been laboriously taught him. The first view is that of Goltz, 
who considers that the animal has to learn to use his imi)er- 
fect visual i)erceptions before his intellectual faculties (which 
are presumed to be unimpaired) can respond to them in a 
proper way. The second view is that of Munk, who speaks 
of this form of imperfect Wsion as '* psychical blindness," in 
contrast to "absolute blindness," which is the result of de- 
struction of the optic fibers. The condition of the animal 
resembles that of the new-bom. Retinal imi)ressions have 
no associations connected with them. During the period of 
lecovery the animal has to acquire a new memory, as it 
were. 



lyU ^^^^^^ TEE BMAm. 

With this distinction cleai^ly in mind, we are prepared Ib 
discuss tlie views of Ferrier, Goltz, Munk, Ijuciani, Tambnrm 
Yeo, Dalton, and others respecting the exact seat of UieTisBii 
centers within the cortex cerebri. 

Goltz, in his exi)eriments upon dogs, was unable to xwf 
nize any distinct areas which presided exclusively over riani 
impressions* He insists that disturbances of general semabil 
ity accompanied the impaii'ment of vision produced by di- 
straction of the convolutions, and that the results deijeodri 
upon the amount of brain-substance removed or desttoyei 
He found, however, that the locality operated upon influeiioii 
the phenomena wliich followed, and that i^eoovery would tab 
place if the injury was not too extensive* Goltz destn>ycA 
the brain by making a hole, or a number of them, Ihrmi^ 
the skull, and using a forcible stream of wafer to wasli umwf 
the brain-substance* The faults of the met hud niny firr«itiiit 
for the negative results obtained by it. 

Ferrier investigated the subject chiefly upon the monkej 
tribe (the nearest approach to the human race) and arrived si 
conclusions of a more x>usitive character. This observer was 
led to adopt a more certain way of limiting the injury donelo 
the cortex than tliat of Goltz, His conclusions may betbil 
summarized: When the *' angular gyrus"— a convolution of 
the parietal lobe, so called frum its shape, since it forms i 
sharp angle (see Pig, 22) — was destroyed upon one side anly, 
the vision of the opposite eye was destroyed for a time, bnl II 
eventually regained its powers. If the angular gyrus of eadi 
hemisphei-e was simultaneously destroyed, the lo^s qf jtigU 
teas permanent and both ej es were equally affected. Hence 
it would appear that each hemisphere is in some way con- 
nected with both eyes, because unilateml destruction of tbb 
convolution does not create permanent blindness, as it would 
do if the opposite hemisphere did not come to its relief. Dal- 
ton has lately confirmed the views of Ferrier by exx)eriments 
made upon dogs, thus tending to confute the view of Golu 
that the effects of cortical lesions depend more on their extent 
than on their position. The animals operated uiwm by t 



I 



i 




THE CORTICAL AREA OF VISION. 197 

observer remained permanently blind, althongh the lesion was 
unilateral. 

Mnnk, on the other hand, has confined his experiments 
chiefly to the occipital lobes of the cerebrum, and has appa- 
rently demonstrated the existence of a ''visual area,'* differ- 
ing in position and of much wider extent than that of Ferrier. 
He maintains that certain parts of this region can be shown 
to preside over limited portions of the retina, and that blind- 
ness of circumscribed spots in the retina can be artificially 
produced. He states that the '* absolute blindness" thus cre- 
ated is commonly associated with ^^ psychical blindness," from 
which the animal may recover by proper exercise and train- 
ing, provided the whole visual area is not destroyed. This 
anthor attributes the recovery to a dei)osition of new visual 
experiences in the rest of the visual area. The view advanced 
by Munk is now quite generally accepted as the true one. 
The optic fibers pass closely to the cortex of the angular 
gyrus in order to reach the occipital lobe. Ferrier and Dal- 
ton probably severed them. 

The sixth set of causes of impairment of vision, previously 
tabulated on page 184, has been discussed in part in connec- 
tion with the others. We have a mass of clinical as well as 
experimental evidence to show'that destructive lesions situ- 
ated within the posterior oTie third of the internal capsule 
cause hemiancesthesia on the opposite side of the body. 

As regards vision, the symptoms which sometimes exist 
are especially noteworthy. There appears to be developed on 
the ansesthetic side a partial blindness of the eye {amblyopia 
or hemianopsia)^ and the field of vision for color is remark- 
ably contracted, as first pointed out by Landolt. 

In the normal eye the field for blue is the largest ; next 
comes that for yellow ; then orange, red, green, and violet 
have fields of gradually diminishing size, the last being per- 
ceived only by the most central parts of the retina. Now, in 
connection with hemiancesthesia caused by cerebral lesions, 
the perception of violet first disappears, then of green, and 
later of orange. In some cases, yellow and blue can be per- 



188 



THE BRAIN. 



fectly recognized ; but in tbe higher degi'ees of aiiie8tli€«iiii| 
colors merge into a uniform seiiia tint. Another impof 
fact has been pointed out by Landolt, viz., that the ejf « 
the same side as the lesion participates, though to a Ita^i 
tent, in the loss of color-perception. 

Clinical Deductions drawn from Preceding Paj5^ 
Amhlyopia of one eye can result from lesions inrolriiigl 
optic nerve in front of the e/iiasm^ or possibly (!) [n>m ( 
of the internal capsule. If from the latter, the field fori 
perceptions will be found to be maikedly contmcted uri 
vision will be wanting ; both eyes may he affected, the 
marked changes being found, however, in the eye opposite i 
the seat of the lesion. 

Hemianopsia may occur when the occipital lobes (c 
the cortex of the ciineus), Wernicke\s tract, the piilriiitf i 
the thalamus, the optic tracts, or the optic chiasm are 
upon or destroyed by lesions of, or in the re^on ot 
cerebrum. It is evident, therefore, that the tiephine 
always afford relief of this symptom. When sypMlitic j 
mata may be suspected, the prognosis iB extremely favctrati 
if active treatment be employed. The variety of hemiand 
often indicates the seat of the lesion with gi-eat exactnc 

H paral//sis (in any of its forms) coexist with heiuiaDc 
a valuable guide will often be afforded in determining the i 
tent of the lesion. 

Crossed paralysis of the *' olfactory nerve and body 
indicates a localized pi-essure which is chiefly exert4*<i npcF 
parts within the anterior fossa if the sJcuIL The motor Iwcl 
is probably involved by ujiward pressure ui>on the raudate^ 
lenticular nucleus, or the fibers of the internal capsule, %ki 
accounting for the hemiplegia of tlie opposite half of the bodj 
The olfactory nerve, which lies near to the optic chif 
affected by pressure in the downward dire(*tion, and the i 
chiasm or tract may be simultaneously involved ; hence a In 
of smell in the nostril od the same side as the lesion may 
exist with some form of hemianopsia, as well as with a ci 
hemiplegia. 



CBOSSED PABAL7SIS AKD CHOKED DISK 



im 



Crossed paralysis of the *' motor-oculi nerve and body"' 
type indicates a lesion situated within the cms cerebri. If 
hemianopsia be present in connection with this condition, it 

i>ruves conclusively that the optic tract, which lies in close 
elation with the eras, issimnltaneonsly affected by the leeion. 
I\^e find, therefore, that the eye on the same side as the lesion 
B blind in its temporal half if the t>ptic tmct lie involved; 
hat it can no longer be turned toward the nose or made to act 
in parallelism witli the opposite eye ; that the pupil is dilated ; 
and that the upper eyelid droops over the eyeball, giving it a 
^Bleepy appearance. On the side opposite to the lesi«jn the eye 
^■k blind in its nasal half, and the body is heniiplegic. There 
^Pare few conditions which are of greater clinical ituportance 
f than this tyi>e of crossed paralysis, because the seat of the 
lesion is i)Ositiveiy indicated. 

Choked disk is a eomm<ui symptom of lesions of the base 
of the cerebrum, and of any intra-cranial disease whicli pro- 
duces a gradually increasing pressure. It is specially diag- 
nostic of tumors. It is not associated with impairment of 
vision until late, so that it is often unsuspected wlien present. 
^The ophthalmoscope is necessary for its detection. It may 
Hksoexist with hemianopsia, and is always bilaterah It is a 
^positive contm-indication to trephining. 

Lesions at the base of the skull may cross the mesial line, 
|i and still involve only one optic tract. If this occurs, the 
Hkemianopsia will be accompanied by other symi>toms of diag- 
nostic importance, no longer confined to one side. Double 
I anosmia, general paresis or complete paralysis, general an^BS- 
thesia, and paralytic symptoms referable to both eyeballs, 
might be thus produced. Lesions of this character are more 
liable to affect the chiasm of the optic nerves than the optic 
tracts ; in either case, however, hemianopsia would result, 
and its type would be a reliable guide to the seat of pressui*e 
(see Pig. 43)- 

{grossed paralysis of the ** facial nerve and body type" is 
,ot as liable to coexist with hemianopsia as the two forms 
previously mentioned. The reason for this is a purely ana- 




mo 



THE BEAIIT 



tomical one. The symptoms of facial paraiysiB are Iwi^ 
volved to be given here in details 

Uncomplicated hemianopsia indicates that no proasRl 
effects are exerted iiiion the motor or sensory fnojecwl 
tracts, or adjacent nerves. 

Aphasia sometimes coexists with hemianopsia, I \tfi\ 
met with two instances of this kind. In one there irassl^ 
paresis of the left side, tending to prove that aphasia < 
cur with lesions involving the right hemisphere, 
cored with specific treatment. We must attribnte thede 
opment of this compliration to pressure upon parts in l 
neighborhood of Broca's center, or to lesions of the is 
capsule, where the speech tract comes in close rehition to tl 
optic fibers (Fig. 39). 

Lesions confined to the crus cerebri seldom crf^te in 
ment of any of the special senses excepting that of the 
Tliese cases are not associated with impairment of inteUi«| 
usually of speech* It has been claimed that severe 1« 
cause paralysis of the bladder, but I have never encoiiiit4fr 
it. Many points of interest pertaining to lesions of the < 
will be considered later. 



THE CRURA CEREBRI. 

If. after the removal of the brain from the sknll, the \«^ 
of the cerebrum be examined, the adjacent ^psLrts being left 
intact (Fig, 28), it will be perceived that the cnini ceHsi 
emerge from the upper border of the pons Varolii, diveig^ 
Jrom one another, and then disappear in the cerebral ht 

pheres, passing beneath the optic tracts. A space is th^ 
left between the crura, in which may be seen the eo-caf 
''posterior per/orated space'' (where the vessels en for tl 
brain to supply the optic tlialamus), and the "^^corponi mi 
illaria'' (Fig, 37), which are formed by the anterior pillars < 
the fornix. 

On the inner aspect of each cms, near to the ani^le 
divergence from its fellow, may be noticed several buniUes i 



THE CRU8 CEREBRI. 



201 



.bers which issue from its substance to form the third cranial 
r " motor-oculi " nerve of the corresponding side. The 
Toove, from which these bundles escape, may be considered 
8 an external indication of the separation of the fibers con- 
fined within the cms into two bundles (the '^ basis cruris j^ 
r ^'crtcsta^^^ and the '^tegmentum cruris ^\ which we have 
Iready discussed (Fig. 46). The larger portion of the cms, 
rhich lies anterior to this groove, is the *'crusta'' ; while the 
* tegmentum " is the smaller or i)osterior portion. 

K a cross-section of the cms be now made, it will be per- 
eived (Fig. 46) that the Crusta and tegmentum are separated 
>y a tract of dark-colored gray substance, the '^ stcbstantia 



Left ball; designed to show the relft- 
tioot of certain iNirU to one another. 



Right haU; designed to show the two 
main tubdivUions qfthe erui. 




^Lateral 
( groove 



ko. 45.— il diofframmoHc representation by the author of the parts seen in a horisMn- 
tat ero u a eet ian on a level with the euprrior quadrigeminal body. 

. f., corpora quadrigeniina ; 8, JV., substantia nigra ; R. N.^ red nucleus ; S,, aqueduct 
of SjlTius, surrounded by its gray matter; q. /., tract of trigeminus nerve root 
(quintus tract); p, /./., posterior longitudinal fasciculus. 

iiffra^ of Soemmering. This collection of nerve cells comes 
o the sur&ce, on the inner aspect of the cms, at a point 
irhich corresponds to the escape of the fasciculi of the third 
iranial nerve (the sulcus ocalO'Viotori)^ and, on the outer 



THE BRAIN, 



n^spect of the cms, along a grcKJved line (the hiUrai *\klat^\ 
The construction of the two main snbdirisions of ibi?f»' 
and its collections of gray matter must be considered fitp 
mtely. 

The Crusta or Basis Cruris (proper cerebral pfiu 
c&?).— This portion of the cerebral ped ancle lies TPDtnil ^. 
the sulistantia nigra, and is formed almost entirely <•( ^^ 
dies of fibers running longitudinally, and continuous W^ 
with those of the pons Varolii and medulla oblongata \fiL 
8), It is semilunar in section— the concave surface of lif 
substantia nigi*a projecting into it (Fig. 45), 

Those bundles which lie adjacent to the sufistantui iripi 
are smaller than the rest and are partially separated by pi*- 
cesses of this gray mass (left half of Pig. 45), They 
been named by Meynert the ''stratum intermedium,^ 
origin and termination differ from those of the bundles wi 
lie more anteriorly. They serve to connect chiefly the 
of the substantia nigra with the reticular formation of 
pons and medulla, although a few pass upward to joiii 
lenticular nucleus (Meynert). 

The main tracts of the crusta are a direct prolon, 
downward of fibers of the internal capsule of the cerebnm 
(Fig. 8) and corona radiata. These fibers are contilitKnis 
below with those of the anterior pyramids of the mediilli 
oblongata, at the lower part of which ganglion the majority 
of the bundle?s decussate and pass down the lateral colunuif 
of the opposite side of the spinal cord as the ^-^trrauei 
pyramidal tracts ^^ (Fig. 46). The ganglia of origin are pc* 
sibly the nucleus caudatus and the nucleus lenticulariH, b 
more probably the cells of the motor cerebral gyri. 

The bundles which are situated in the lateral or ou 
part of the crusta are stated by Meynert to pra*?ent pecuHan 
ties of origin and distribution. He believes that the fihen 
which compose these bundles arise from the occipital^ pariet 
and temporo-sphenoidal lobes of the cerebrum (the sens^ 
area\ and enter the crus without any apparent connectioi 
with the cells of the basal ganglia ; that they decussate in 






MOTOR FIBERS OF CRU8TA CRURIS, 



tidal JIden of iha 1 
erebral hemisphere, t 



a b 

0\ >^'>"^t Pv^^^^^M«n of 

,^^\ ^\^S ^ unil buiuiJBphere. 



the right ceie- 



of Tflrck^s eoV 
or left hAlf 



of the croMed 1 
oldal oohimn or A 
iftrid«ofoord. ^ 




fDecnimttioii of th© croued p^ra- 
'"7 midai tracts within the me- 
K diiilA oblongata. 



Ftb«rs of Tflrrk's column of 
rtgfatiiairofcord. 

r Fibfir of the crofeed prra- 
tdMaI colomn of the right 
lilde bf cord. 



, / Colamn of Tflrck of right 
|_ ilde. 



?,„ J Direct cerebellar col- 

1 umn of right side. 

^ . f Crossed pyramidal 

I colamn of right 

^ side. ^ 



44.—^ diof^ram detigntd hv the author to »how the course of the fibers of the 
cerebri (motor) after they leave the pyramids of the medulla. 



r§ei pyramidal tracts (o-o, b-b) paM down the column of Tiirck (T^s Col,) of the 
me tide of the cord. The crossed pyramidal tracts (o-c^ d-d) pass down the so- 
IM erotsed pjnunidid column (C. P. C.) of the opposite side of the cord ; B's C^ 
mrdach*! cotomn ; €Ps C, Goll'a column ; 2>. C. C, direct cerebellar colamn. 



204 



THE BRAm, 



medulla, above the point of crossing of the lateral pyramids 
fasciculus just described; and, finally, thiit they can be m<«| 
to the posterior column of the opposite side of the spim i 
cord. 

Plechsig has shown that the bundles of the crusta 
nearest to the mesial plane of the body are developed 
than those of the main pyramidal tracts, and are therf^fop*^ 
be considered as a distinct formation. 

Finally, there remain to be added to the four sets of 1 
aheady described certain bundles which are connects 
the cerebellum and which interlace themselves with thel 
of the cerebral tracts — chiefly during their passage throo 
the pons Varolii, 

In suratnary, it may be said that the crusta is compOMli 
five sets of bundles, each of which has probably a funeti 
of its own, and certain individual peculiarities of distrib aliaij 
which distinguish it from the others. 

I have not mentioned among these five distinct trmcS^ 
the crusta the tihers of the third cranial nerve whirh ait 
depicted in the diagram (Fig. 45). The motor-octili fihew 
escape from the eras in the region of the sabstantia nigri) 
and are, therefore, not associated with those bandies wlxich 1 
anteriorly to it 

The ganglia of origin of the fibers which help to com] 
the crusta are believed to be as follows: (1), The ni 
caudatus ; (2), the nucleus lenticularfs ; (3), (he stiistanti 
nigra; (4), the motor cerebral convolufians ; (5), poesibt 
some parts of the sensory area of the cerebral cortex. 
first and second, as well as the fourth and fifth, have alrea<3 
been described as parts of the so-called '* corpus striatal 
and the fibers of the crusta which are anatomically n^late^d 
them have received more or less notice in previous pages, 
is necessary, therefore, to confine our remarks here only 
the third of these ganglionic masses. 

The SrnsTAXTiA Nigra (fow^ ///V/^r).— This collecr ion 
gray matter separates the fibers of the crusta from thojq? of 
tegmentum cruris (Fig. 45). Its Umits extend vertically 



THE SUBSTANTIA NIORA. 206 

9 the posterior border of the corpora albicantia to the upper 
a border of the pons Varolii. The nerve cells which compose it 
i^ are darkly pigmented. This gives it the appearance indicated 
by its name. It is thicker in its mesial portion than laterally, 
r and sends out processes which penetrate between the longi- 
% tadinal bundles which form the crusta. One very marked 
3. projection, in which the nerve cells are smaller and more 
numerous than elsewere, marks the dividing line between the 
c inner and middle thirds of the crusta. 

At its inner border, the substantia nigra is traversed by 
the fibers of origin of the third cranial or motor-oculi nerve 
(Fig. 45). Some of these fibers also pass through its inner 
third. 

The cells of the substantia nigra are supposed to aflPord a 
^ communication between fibers of the cerebrum and some bun- 
j dies of the cerebellar system of fibers. Certain spinal fibers 
also terminate within them, according to Meynert and others. 
When we consider how marvelous it is that the muscular ap- 
paratus can act in perfect harmony with the impressions 
which we are constantly receiving by means of sight, hear- 
ing, and the tactile sense, as exhibited in the finer feats of 
balancing, dancing, etc., it becomes evident that the nerves 
which carry such sensory impressions to the nerve centers 
mnst be brought somewhere into a close relationship with 
the motor nerves which infiuence the muscles of the ex- 
tremities. It has been already shown that an animal de- 
prived of the cerebral hemispheres (but not of the basal 
ganglia) can perform feats of equilibrium with perfect exact- 
ness. It is manifest, therefore, that we must look to the 
basal ganglia of the cerebrum, or to parts associated with 
them (chiefly the cerebellum), as the probable seat of these 
coordinated movements. To what extent the cells of the sub- 
stantia nigra enter into this complicated mechanism is as yet 
problematical, but there is little doubt that it constitutes one 
of its important factors. 

The Tegmentum Cruris.— The fibers of the posterior di- 
vision of the cms cerebri (Pig. 45) have the following ganglia 
10 



206 



THE BRA IX. 



of origin: (1), The optic thtdami ; (2), tlie corp^a 
gemina ; (3), the corpora geniculaia ; (4), the corpora i 
illaria; (6), the ansa peduneularis ; (0), the pineal fflad^l 
(7)^ the red nucleuB ; (8), the ganglion qf the habenuhi. 

Most of these have been ah^eady consideretl. The 
mainder will be described in connection with the fibet^s i 
arise from them. 

The tegmentum is composed of small longitudinal ban 
of nerve fibers, more or less extensively interlaced by iitb 
which are directed transversely.* The bundles are also 2 



' The distinct nerve tracta within the tegtncnttim cruris have been latetv \ 
Fleclisigt with a view of det<*Tmining the relative periods of development of eiidi,i 
potutively determiaiDg: their couree and probablt* functlans wttli e^ome ap}*'^'*'*^ ** ' 
curacy. It may be well to aummanzc the resuUfl of these invc^tig^tiona^ «» roAlftit^ 

h The xuperior pedunefe of (hfi ctreldlum {** ptOcemnB e eerebello atl le«tc«*ift 
earlier anatomists) was found to arise (1) from the dentate nucleus, . T: 

cerebellar coitex near to the worm. By the first point of origin, it ?i* bix» 4lji 

intimate relationship with the restiform tracts of ihe cord and some paru oi \ht^~ 
bellar cortex. Some of lu fibers appear to terminate in the red nucleus of tb« op|Hitf 
dlde. The rcinaiDing butidlea terminate, noeording to this author, in the lenticular m^^ 
and the corona radiata* 

2. The Icmnisctti ^eems to consist of two distinct «ets of fibers ; on« ot «Bc^ foi^ 
goes descending degeneration, and the other ascending degeneration when fi«fNitmil4d ttm 
Ihcir tr«*phie center;*. We can, thc»*efore, conclude that they carry impul»«r$ that etm 
ipond to the form of dcj^cneration that they undergo, one centrifugal txnd ii» cidmrcf^ 
tripetal. The oentrlfugal conducting tract eompHsK^s two thinls of the entir«^ bulk tl dt 
lemniscus^ It ariaea from the external division of the lenticular nuclt^us of tlic C9qm 
striatum and takes the following course from ahoro downward: (1) acrr^a^ titc iMlfsi^ 
capsule ; (2) above the body of Luy^ ; (it) to the outer eidc of the red nurleua ; (4) tbfO^ 
the substance of the pons, lying dorsal of the pyramidal tracts ; (5) it tertiuu*ic# ia iki 
olivary body. The centripetal conducting tract arisen at the sicnsory (lecus9«rkia of ite 
medulla and then pas^c^ through the pons and afterward behind the red nuc4e«i at tl« 
te^eotum. It then turns Ix^ncnth the corpus quadrigenunum inferior ftfid tlic pitltter« 
and becomes lo?t in the corona radiata. 

8. The pout trior hn^ifudinal fiacieulus, Tliif bundle aeemfl to be cotnpoi^ of Mmt 
of aKiiociation between the nuclei of .origin of the cranial nerve roota, chiefly II^Me of tl* 
third, fourth, and Biith nerves. It can he shown to be connected, below, with th» ^rt»> 
rior columns of the cord, thns demonstrating that it is physiologically related C4> nytdts. 
Superiorly, it is continued into the gray lining of the third ventricle. TliU tr»ci b tfct 
finsi to be developed in the hrain of the fwtufi. It Uc» immediately hencAib tbe mj 
lining of the fourth ventricle. 

4. Tbe formath retimlaris. The fibers that become intermingled in thif atruictaff 
are not yet definitely settled. Flcchsig'fi researches seem to eatablish the pt^t^t^mwt 
fibers that descend from the quadrigeminal bodies, as well as some that ascetMl ft«ai lit 
poaierior columns of the cord, 

ti. The ffmerul nen^ory tract from the periphery to the cerebral cortex mf^m t»^ 
formed above tbe medulla by the union of fibers derived from the superior pedoftcb uf Ibt 



FIBERS OF THE TBOMEKTUM CRURIS, 207 

rated to some extent by collections of gray matter contain- 
ing scattered nerve cells. Some of the bundles form well- 
defined tracts. These will demand a separate description. 

The Posterior Longitudinal Bundle.— This tract of fibers 
(Fig. 45) lies between the gray matter underlying the aque- 
duct of Sylvius and the so-called *' reticular formation,^ so 
well defined in transverse sections made through the upper 
part of the pons Varolii. If traced upward, the fibers which 
compose this bundle seem to become lost in the region of the 
posterior commissure, either by becoming intermingled with 
the nuclei of origin of the third and fourth cranial .nerves 
in the mesencephalon, or by a dispersion in the reticular 
formation. Below, they api)ear to be a continuation of the 
fibers of the anterior column of the spinal cord. It will be 
again referred to when the architecture of the medulla oblon- 
gata is considered. 

Th£ Superior Peduncle of the Cerebellum. — This tract will 
be discussed in detail in connection with the description of 
the cerebellum. It has been already referred to when the 
caudate nucleus of the corpus striatum was under considera- 
tion« It bears an intimate relation after decussation with the 
red nucleus of the tegmentum (Pig. 46), from the cells 'of 
which some accessory fibers are probably given to it. The 
decussation of the fibers of this tract can easily be demon- 
strated in all cross-sections. It is claimed by Luys that this 
handle of fibers enables the cerebellum to reenforce the cells 
of the corpus striatum. Some anatomists claim that the optic 
thalamus receives some of its fibers. Flechsig traces its fibers 
to the lenticular nucleus and the corona radiata. 

The Tract of th^ Fillet {Lemniscus TVac^).— This tract has 
been the subject of much investigation. At the upper level 

eerebelliim, the sensory diTision of the lemniscus, the ascending fibers of the formatio 
rctknlArii, and a few fibera of the posterior longitudinal bundle. These tracts unite at 
ftboot the l«Tel of the quadrigeniinal bodies. They then become joined by fibers arisiuL' 
from tbeie bodiea and pass into the posterior part of the internal capsule, and radiate, 
oppodte the poaterior third of the thalamus, into the cortex of the parietal and temporal 
regloiia tad the prwrniieus. The term ** corona of the tegmentum ** is applied to the 
tneCMA whole. 



208 



THE braj:^ 



of the pons it appears as a flattened bundle of lonpi 
fibers at the anterior border of the reticular formatii 
45)* It ia prolonged cephalad into the corresponding 
the tegmentum. Some of its fibers jkiss obliquely ou 
and curve over the cerebellar peduncle at the side of the 
In the latter respect, they i^esemble the course of the nidi 
medullary velum, whose fibers reenforce those of the 
A layer of gray matter covers the fillet externally. The 
of this tract aie thought by some anatomi^its to be chiefly 
tributed, above, to the inferior qimdriyeminal body. 
they appear to be connected with the nuclei qf the pai\ 
columns qf the spinal cord. Some of its fibers prohaWvW 
long to the sensory tracts of the cord. The name *^lemniM>cm^ 
is applied to the curved fibers of the fillet. 

The views of Flechsig respecting the composition of 
fillet have been given in a foot-note on a preceding page. 

The mesial fibers of the tract of the fillet are belieTed bf 
Meynert to pass upward in the intermediate sti^atnni of tk 
crusta. 

According to the researches of Forel, a middle portkjn d 
this tract presents some peculiarities of course and distribo- 
tion. Some pass, according to this author^ upward tlirough the 
reticular formation, and subsequently join the corpus ulbiniitf 
or become lust in the longitudinal bundles ; a few of tta 
lateral fibers of this middle portion pass to the upj>er qaadri- 
geminal body {natis cerebri)^ this bundle being distinguiitlied 
as the '^ upper fillet-' in contnidistinction from the fibeni ot 
the lateral portion of the tract which pass to the lower quad- 
rigeminal body {testis cerebri)^ w^hich are know^n as the •* towf 
fillet:' 

Some authorities claim that the fibers of the tract of tlM 
fillet may be traced into the posterior part of the lateml 
column of the spinal cord, as well as into the anterior eoIoiQii- 

Late researches, regarding the physiological function of 
this tract of fibers, seem to point toward a relationship be* 
tween the lemniscus and the so-called *^ muscular aem^*" 
(Spit^ka and Stair), 



THE LEMNISCUS, OR FILLET TRACT. 

The fillet tract becomes intermingled with the fibers of the 
* stratum intermedium, although it lies more to the lateral por- 
' tlon of the medulla. It is apparently connected above with 
the inferior cori)ora quadrigemina (testes cerebri), although 
some observers think its fibers pass to the cerebral cortex by- 
means of the corona radiata ; below, it is believed to partici- 
pate to some extent in the piniform decussation (Spitzka). 
Some authors are led to believe that this tract is intimately 
associated with the sense of sight as well as with coordination 
of movements. 

E. C. Spitzka has lately investigated the results of a lesion 
of the pons that chiefly involved the fillet tract. The case is 
one of great interest, as bearing upon the question of the 
probable paths of coordination. The prominent symptom 
during the life of the patient was an inability to perform co- 
ordinated movements upon the right side. 

The deductions drawn by this observer, from a careful 
study of microscopical sections of the pons and medulla, are 
summarized by him as follows (" New York Medical Journal," 
March 16, 1884) : 

''1. The so-called lemniscus layer contains in its mesal por- 
tion an individnalized column of fibers of high physiological im- 
portance, which decussates in the so-called sensory decussation of 
Meynert 

*^ 2. The stratum intermedium, as this bundle should be called^ 
for reasons to be advanced further on, is a tract mediating an essential 
factor of voluntary motility — codrdination. 

** 3. The ataxia of movement observed in destruction of this tract 
is not due to a loss of tactile sensibility. The latter was not sufficiently 
impaired to account for the absolute unilateral ataxia attributable to 
the division of the stratum intermedium. 

''4. The stratum intermedium is not purely a centripetal tract 
It degenerates centrifugally. 

" 5. Physiologically, it appears to be, in part at least, centripetal ; 
this is shown by the paraesthesia and hyperaesthesia complained of by 
the patient. 

** 6. While the stratum intermedium is probably the continuation 
of the column of Goll, and, in part, of that of Burduch, toward the 
oerebmm, the secondary degeneration of the spinal part of this (ideal) 
tract advanoea oentripetally, while the cerebral portion degenerates 



210 TUB BRAiK 

oentrifugallj, the point to which both converge being the nodfitf 
tho posterior colimnis* 

** 7. Flechaig's statement that there is no direct eontiniifitiiAi 
the posterior columns into the pinilorm decussation, bat that 
terminate provisiormlly in their uucloii is demonstrated beyond 
venture by this case. 

** 8. While Flechsig is also siisUined in his denial of % §rm^\ 
nection between the so-called npper pyramidal decufisation of MetWP 
and the pyramids proper, yet there \^ an intimato coDnection btttte 
the stratum intermedium and the pyramid of the same side^ ext4<i»^ 

along the known course of the former tract from its decus.^r* • 

the lower part of the pons. It is pos^nible that the coutiect : 
the sensory periphery and the pyramids, which Meynert a 
establish, really exists through the medium of this int^rchai. 
in much lesser degree than the distinguished founder of Ci 
brsl anatomy surmised. 

** 9. The system of fibers which is represented in the fascicuh 9S^ 
ing through the olivary nuclei^ those of the external urciform gnwf 
— and which are not without reason supposed to connect tht^ p<i * ' ' 
columns, or rather the latter, thnnigh nuclear intervention, Vi 
restiform column — is entirely independent of the stratntu intermedias^ 
Nor have the olivary nuclei, or any of the tracts connected iritli Uun, 
a connection with the stratum intermedium. 

^* 10. The vertical fibers of the trapezium appertain to tbo wtnUfm 
intermedium." 

The resnlts of Starr's investigation of a microcephalic hrm 
(lately awarded the Alumni Association prb© of the CoUec*' 
of Physicians and Surgeons) are not in full accord wili 
Spitzka regarding this tract. 

Ganglia of the Tegmentum. — That there is a funedonil 
independence between the cerebral hemispheres and the 
tUAses of gray matter connected with the fibers of the pc*- 
fcerior division of the crus seems to be proved by a comparid^tt 
of the relative development of the two in animals. The optic 
thiilami and corpora quadrigemina are less developed, in pro- 
portion to the weight of the cerebrum, in man than in either 
the ape or deen 

The OPTIC THALAMUS 18 probably associated with the fibers 
of the tegmentum (1) by means of the bundle connected with 
the ganglion of the haheiuda vanarii ; (2) by means of the 
soHsalled lamifKB medidlarea ; (S) by means of the jyostcrhi 



^taiki 



GANGLIA OF THE TEGMENTUM CRURIS, 211 

commissure. Differences of opinion exist between Meynert 
and Luys respecting the relations of special fibers to the 
ganglionic masses found within the thalamus. Some of these 
have been already discussed. Future investigations regard- 
ing the effects of disease of these parts and additional light 
afforded by experimental physiology can alone render our 
knowledge of the sensory tracts of the brain less conjectural. 
The latest conclusions of Plechsig, Spitzka, and Starr are of 
particular interest in this connection. 

The anterior corpus quadrigeminum of either side seems 
to be associated with the special sense of sight, although its 
connections, as well as those of the posterior pair, with the 
fibers of the tegmentum and the cerebellum would indicate a 
more extended function. In previous pages, the structure of 
this ganglion (taken as a whole) and the results of physio- 
logical experiments upon it have been discussed in detail. 
Setschenow has shown that, among the other functions which 
this ganglion seems to possess, it appears to be able to inten- 
sify the inhibitory or controlling influence of the brain upon 
the reflex actions of the spinal cord. Although it is unques- 
tionably connected with the optic fibers, this ganglion is cer- 
tainly not the center of consciousness of visual impressions. 
It seems probable rather that it may be a center of coordina- 
tion between retinal impressions and special muscular move- 
ments. It is stated by some observers that blindness of the 
opposite eye follows its destruction, but this is not accepted 
as proved by all physiologists. 

Impairment of sight may be attributed in many cases to a 
severance of the optic fibers from their connections with the 
visual area of the convolutions. Such an occurrence in con- 
nection with a lesion of the anterior pair does not prove that 
the corpora quadrigemina are centers of vision. They stand 
in no constant relation to the development of the eyes, as is 
proved by the fact that they are largely developed in some 
animals where the eyes and optic tracts are rudimentary 
(Longet). 

Goltz, SerreSy Cayrade, and others have noticed effects, 



212 



THE BUAI^. 



produced by destruction of these bodies, upon thefumlm 
if eqitllihration, Ferrier has confirmed these statemenlf h 
exj)eriments made upon monkeys, fishes^ and rabbUs aL\ 
McKendrick haa been led to the same conclusion by bub 
vestigations upon pigeons. 

Goltz and Vulpian were led to beliere that plaintiff cm 
(as a form of emotional expression produced by sensailoBft 
pain or pleasure) ceased when the corpora quadrigeiiiiiia 
destroyed, Ferrier thinks that this conchision is only pmljj 
true ; because he was able by intense stimulation to e» 
responses in the form of cries in a rabbit whoBe opiie 
had been entirely i-emoved. 

Spitzka employs the following diagram to interpref Ui 
views respecting a supposed relationship betwi^n the inferior 
quudiigeminal bodies (post-optic lobes) and visceral and 
motor innervations (page 213). 

The effects obser\^ed in the pupillarp movemefiis and 
motor reactions aft^r mechanical iiiitation and electric 
lation of these bodies in animals are comparatively unift 
The pupils dilate, the head and eyes are turned to the opi 
side, the ears are drawn backward, the jaws become cl 
firmly, the lips are retracted, and finally complete opi^t 
nos is produced. Various forms of vocalization have 
been observed to follow irritation of the *' testes cerebri." 
is impossible to ^tate which of these effects is due to 1 
tion of the optic lobes themselves and which to the tracts d 
fibers underlying them. The ganglia of the mesencephalon u 
well as the cerebellum are too intimately connected with the 
pons and crura to make any f>o8itive differentiations possible 

Meynert's view that one of the roots of the filth Derw 
can be traced to a collection of large cells which lies adjacent 
to the aqueduct of Sylvius may help to interpret the nwrt- 
meats of the Jaws when the oi)tic lobes are stimulated. We 
meet with simUar manifestations of transmitted imtution by 
means of the spinal cord in tetanus ; and. when these phenom- 
ena am groujied with the movements of the limV)s and trunk 
which are likewise created by excitation of the corpora qaad- 



riidita 




CONNECTIONS OF POST-OPTIC GANGLION 



213 



li kigemina in frogs, fishes, and mammals, we are forced to the 
9 conviction that these ganglia are important factors in the ex- 
^liibition of the physical evidences of paivful sensations in 
{I ^neral. 



POST. OPTIC 
OANQLION. 



POST. OPTIC 
OANQLION. 



it 

ii 



IX PAIR. 



XI PAIR. 




POSTERIOR COLUMNS 
OF SPINAL CORO. 



J^nUkd'a THagram, 



Danilewsky finds that Tnodifications in the arterial press- 
ure^ asaociated with a slowing of the heart and amplification 
qfthe pulse-waves^ follows electric stimulation of these gan- 
glia, and Budge and Valentin claim to have created contrac- 
tians qfthe stomachy intestine^ and bladder in the same man- 
ner. I am inclined to doubt, however, if these phenomena 
are doe to the local effects of such stimulation, because we 



114 



THE BRAm. 



know positively that electric currents are often widdi 
fused. They have been adduced, however, by Penfeti 
proofs (not well esttablished) of the relation of the optirki* 
to the reflex manifestations of emotion. Fear is nol nuft 
monly exhibited, as we know^ by the hnman race as wd! il 
by some animals, by involuntary pa8sag)e of the iiiiiieili| 
faeces, and oceasiomilly by vomiting. 

The relation of the corpora quadrigemina to vision, w 
as some other pathological and physiological facts of cUl 
interest, has been considered more fully in previous papSi 
which the reader is referred. 

The Geniculate Bodies.— These ganglia (Pig, 43) i 
considered by some authors as api>endages to the optic tkir| 
ami and the corponi qiiadrigemina^ because rhey appear i^l 
be associated to a greater or less extent with the 8|>ec:ial 
of sight. Their situation furthennore supports the vi 
Meynert, that they are also ganglia of origin of fiber?* 
tegmentum. 

In the extniial genwulate body the giviy matter to 
miiged in laminse which present, in ci*oss- sections 
tluongh its substance, a zigzag outline, as if the lamina 
been crushed or folded together. The cells of this mafis 
large, granular, and pigmented. 

The internal geniculate body is less intimately com 
with the optic lobes and the fibers of the optic tract, as 
by the latest researches of Flechsig, Gudden, and Gai 
Its gray matter is not arranged in the manner pecnUar toil 
companion, although it is apparently travei-sed by fiberi 
the optic tract connected with both the natis and testis 
bri. The nerve cells of this body appear to effect a decid< 
reduction in the number of fibers which pass through iti. 

Some of the optic fibers pass directly fi'om the optic trad 
to the corpora quadrigeminum without any intarventioa d 
these ganglionic bodies, w hile a few of the innermost bundkfl 
of the optic tract become appai'ently intertwined with tlir 
outermost fasciculi of the cnista, Burdach thinks that hf 
has traced a connection betw^een these bundles and the .sub- 



idl&i 



RED XUCIBU8 AKD PmSAL GULXD, 



815 



fitantia nigra of Soemmering, Mejnert has not been able to 
confirm this view. 

The Red Xucleis of the TEGitENTiM.— This ganglionic 
mass has been discussed already in connection with the supe- 
rior peduncle of the cerebellum, and will be again referred to 
when the (^febelliim is described. It is shown in Fig. 43. 

The Mammillary Tubercle {corpus alhicajis—hnlb of the 
J'andj:). — The situation of this body, as well as its method of 
formation, is shown in a preceding diagram (t^g, 37). Its 
structure has been discussed in connection with the thirtl 
ventricle. It is classed by Meynert and otliers amt)ng the 
ganglia of origin of the tegmental tili>ers. 

The Pineal Gland.— This body (the mn€trium\ which 
resembles a fir-cone in shape, lies above and between the two 
upper quadrigeminal bodies (Fig. 37). It Ls often 8i)oktm of 
as the ^' hypophyns cerebil^'^ although improperly so acct»iti* 
ing to the view of MejTiert. The opiniun of Luys that this 
body is directly continuous with the gK\v lining of the tlnnl 
ventricle is opposed by Arnold, who claims to have demuii- 
strated that it is sepai-ated from it by a medullary layer. 
Meynert regards it as one of the ganglia of origin of the teg- 
mentum cruris* since it is connected with the crus by means 
of the posterior commissure. It is also connected with the 
medullary substance of the cerebiiU hemispheres by means 
of its peduncles. 

The cells which are found within the gray substance of the 
pineal gland are of two sizes, one Ibfi and the other 0/* in 
thickness. Tliese cells are packed more closely than in the 
other cerebral ganglia* 

The pedicle of the pineal gland {hahemda) is believed by 
Meynert to be directly connected with the posterior com- 
missure of the third ventricle, as well as with the fomix 
anteriorly. - 

In microscopic structure the pineal gland bears a resem- 
blance to the anterior lobe of the pituitary body. A nnmber 
of hollow follicles may be denionstrated within it, which are 
filled with epithelial cells, and a gritty matter— the so-called 



216 



TBE BRAnr. 



\ 



(wenmluB cerebri or brain-sand. This eabalons matetUl] 
also found upon the exterior of the gland and its jiedancla 

During the development of the brain the r ^^ ' ^bidf ] 
pears as a hollow excrescence from the part n .__ Itol 
the third ventricle. Subsequently, this diverfjc;n]am beeowl 
cut off from the ventricle, and tubes develop within it. Fiml 
ly, these tubes are seen to separate into isolated vesicles, wlii j 
are, as a rule, spherical in shape. 

THE AROBITEOTURE AND FUNCTIONS OF THE CERKBKLLni 

The cerebellum or " hinder-brain ** consists of two lalinii 
hemispheres^ joined together by an intermediate portion wWdl 
is called, from a fancied resemblance to a worm, the ** vi 
form process." The peculiar appearance of this pn)ce88 b 
partly to its shape and partly to transverse ridges and fm 
which are very apparent. When the under surface of 
cerebellum is examined, this process appears as a well 
projection, the ""^ inferior vermiform process.^ On the u] 
surface it is only slightly elevated, forming the scKcalled ** 
perior vermiform process " In birds, as well as in some 
mals lower in the scale, the vermiform process alone 
It is the part first developed in mammals* In most mami 
moreover, it constitutes a distinct central lobe, clearly del 
kated from the h^teral portions — the hemispheres of the cere- 
bellum. 

The cerebellar hemispheres are separated behind by ad€«p 
notch. Below, a deep fossa (the valleeulaX which ir condtiv* 
ous with the notch seen posteriorly, lodges, the inferior venni 
form process. This hollow also receives the medulla in front 
and the falx cerebelli behind. The hemispheres are ooofes 
on their lower surface, and tend to partly conceal the inferinr 
vermiform process : aboie, however, they are somewhat fljit* 
tened in the center, and slope downward toward the sides* 

* Tli£ vemii/orm proema Afvpcftfs to bet ootnpltfte gAOglioii in ittelf, tmimiitwl t^ 
Ha own octrc tracts, TUo «rth«Sar hemitph^n'm iirv ttddod, In the hl^jlic? gratteft of tf»> 
idaIs, in pfoportlon to the dofelopment of the oerebftl lobM, 




THE CERBBELLVM, 



217 



rasing the slightly elevated superior vermiform process to 
less distinctly outlined than the inferior process is. 
j^^ The cerebellum measures about three and a half inches 
^nansversely^ about two and a half inches from before back- 
^■rard^ and about two inches in depth at its thickest portion, 
^although it thins out at its lateral borders. 



FifJ. 47. — CfrtheRum ami mftfulh &hfotipaia, (nirscliield.) 

, 1, »Tfpns dcnlatum ; 2, tuber nimnliirc; 8* section of the initldle peduncle; 4, 4, 4,4,4, 
I forming the arbor \\u»i; 5, ft, oUvary hody ot the niedulln ohIongatA; 6, an- 
i;»)'nuuiid of the medullA oblongsta ; 7, upfnT extreuiitj' ol' the iifiitial cuiti 

'Tile surfaces of the cerebellum are everywhere marked by 
p, closely set, transverse, and somewhat curved fissures. 
\tem are often of considerable depth, the larger ones conceul- 
ig many folia wldch do not reach the surface of the cen?bel- 
jm. Some of these fissures are better marked than the rest, 
^thf* most ronspicuotis one being the f/reat horizontal jUsure^ 
rhich starts in front at the middle peduncle, and extends 
round the outer and posterior boi-der of each hemisphere, 
L4ug prolonged into the jwsterior notch, where it joins with 
fellow of the opposite side. This fissure separtites the 
Esllum into an upper and lower portion, which correspond 
the upper and lower surfaces. Each of these portions is 
(ewi2«e subdivided bv fissures, somewhat more distinct than 
rest, into small lobes. The names of these lobules can be 



ittliii 



^tMk 



318 



THE BE Am. 



found in any work upon descrijjtive anatomy. The foAiifl 
and flocculV are the more important The vermiform pv I 
cess, or ''worm/- is also subdivided into lobules. Fiji I 
logical experiment or pathological research has not yet poi] 
tively located any special functions in these lobules, m \ 
they are of use chiefly in describing the situation of 
of the cerebellum and the course of fibers to the cef«bfli| 
cortex. 

Sections made through the substance of the oeret 
show a beautifully foliated or arborescent appearance; Da»i| 
*' arbor- Yitse" in consequence of the medullary or white *«^| 
stance of the ganglion being prolonged into the lamin;e. 1V| 
main branches of the medullary substance, or groups of tbrttj 
correspond to the lobules of the cerebellum. These ant ooi'] 
nee ted, as the cerebral convolutions are, by festoon-like S 
(fibrie proprisB). The medullary substance is more abnndiitl 
in the hemispheres than in the worm (vermiform process^. 

In the center of each hemisphere a nucleus of gray mattet^l 
the so-called ''corpxis dentaium,^ is seen in all vertical aalj 
transverse sections of that region. In structure it reseml 
that of the olivary body of the medulla oblongata, haniigi 
wavy layer of yellowish-brown substance externally, an 
white matter in its center. At its upper and inner port 
wavy layer is interrupted, so that the plicated capsule is nd 
complete. The fibers which are contained within tlie pi 
cerebelli ad cerebrum (superior peduncle of cerebellum): 
the valve of Vieussens may be traced, in part, to the 
^^ dentatum. 

^H Stilling, who has made elaborate researches respecting the 
W minute structure of the cerebellum, describes three other eot 

■ . lections of gray matter within the white center of the hemi- 
W spheres. These are named the *' nucleus embcdiformis^" tbe 
I ^'niwleus globosus,^^ and the '' nu4;lem fasUffiu^ Them 
I nuclei are not distinctly isolated in all parts, but are coa- 

■ nected here and there with one another, and with the oorpa? 

I 

m^ derive 



' Tlie Jtocculm \» believed by »omc Auihors to be directlj ■siOQlited with m 
derived from tbe pacuiaogaAtriti oervo. 



CEREBELLAR NUCIBI AN^D CORTEX. 



219 



dentatitm. Their fiinctiong are not yet determined. The 
^"^ nucleus fastlgii^^ \s often called the *' nucleus of the ven- 
tricular roof " (Spitzka). It is sitnated in the white mass of 
the womi, and lies in the roof of the fourth ventricle. It 
probably recei\^es fibers of the audUary nerve root and the 
trapt'Zium. This nucleus is separated from its fellows by a 
tliin septum of white matter. The other two nuclei described 
by Stilling lie in intimate relation with the dentate nucleus of 
the hemisphere. 

The cerebellum, as a w^hole, is described as possessing 
three peduncles. These are collections of nerve fibers which 
pass out from, or into, the substance of the hemispheres* 

The superior peduncles {processi cerebelli ad cerebrum) 
are directed upward and forward from the mesial part of the 
hemispheres. 

The middle iieduncles (processi cerebelli ad pontem) 
emerge from the lateral part of the hemispheres and pass to 
the pons Varolii. 

The inferior peduncles [processi cerebelli ad meduUam) 
escape from the heraispheres of the cerebellum between the 
other twoj pass forward outside of the superior peduncles to 
reach the lateral wall of the fourth ventricle, and then turn 
sharply downward to become the so-called '^restiform l»odies" 
of the medulla oblongata. Eacli of these processes will be 
considered separately. 

We are now prepared to consider the minute structure of 
the cerebellum and its processes. The various theories which 
have been advanced in regard to the prcjbable functions of this 
ganglion ran be intelligently discussed only after some knowb 
ledge of its connections with other regions of the cerebro- 
spinal system. Experimental physiology frequently conflicts 
with the observed effects of pathrdogical lesions of the nerve 
centers. 

THE CEREBELLAR CORTEX. 

The external gray matter of the cerebellum differs in its 
microscopical appearance from that of the cerebrum, which 
has been described in a previous lecture. It consists of three 



220 



TEE BRA IK 



layers^an outer, composed of both cells and fibers ; a middle, 
consisting of large oellj^, termed the '' corpuscles of Purkinje ' 
and an inner, which is reddish-gray in color and of a granular 
structure. 

In the outer layer most of the fibers have a direction at I 
right angles to the surface of the cerebellum. The greater 
proportion of these fibers are simply the prolongation of the 
processes of the large cells of the middle layer {cells of Pur- 
kinje), Others are fine, tapering fibers, which seem to rest 
by a broad base on the pia mater, which rovers the outer 
layer. These fibers make up a dense felting, inclosing free 
nuclei and scattered cells. The cells of this layer ai'e gmnule- J 
like bodies^ the larger of which are af)parently connected with 
the i>rocesses of the cells of Purkinje. The smaller probably 
belting to the matrix ; the larger are supposed to be nervous 
in function. Along the innermost portion of the outer layer 
nerve fibers may be also demonstrated, which run paraOel | 
with the surface of the cerebellum. 

The middle layer is characterized by the peculiar cells' 
found imbedded in it— the ''cells of Purkinje," Most of 
these cells are flask-shaped, although a few are irregular in 
form. The long axis of tlie cell is placed at a right angle to 
the free surface of the cerebellum. Tlie diameter of these cells 
varies from -g^ to ^tsVo ^^ ^^^i inclL Two sets of processes may 
be demonstrated as arising frtuu these cells, viz., one passing 
through the outar layer of the cerel)ellar cortex and one pass- 
ing through the inner layer. The fonner are of large size, and 
are connected, in some instances, with the corpuscles of the 
outer layer ; others pass directly through the layer to become 
lost at its surface. In either case they subdivide repeatedly 
in their passage through the outer layer. The inner set of 
processes are fine and undividi/d, and pass into the granule 
layer, where some probably become continuous with the axis- 
cylinders of nerve fibers composing the medullary portion. 



' The bodies of theao oelb are coloss&l (aixtj to seven t? millimetres in lengtb^ aod 
twenty to thirty miUimetrea in thielctiess), Thev appear to be iaclosed uiihin a loose- < 
fitting cmpsule, formed of coDDCctiro-tLidiie fibers (Obcrstciaer). 



LAYERS OF CEREBELLAR CORTEX. 221 

k The inner layer ^ called the "granule layer/' lies next to 
ufihe meduUary center of the cerebellum.* It consists of gran- 
it iile-like corpuscles, which are imbedded in groups in a gelati- 
nous matrix. Nerve fibers can be demonstrated to join with 
i. the processes of the cells of Purkinje within this layer. The 
* oells of this layer are both round and angular. Each consists 
rof a nucleus, a thin envelope of protoplasm, and processes 
; which unite with the plexus of nerve fibers in its vicinity. 
I Tliey measure from ^^ to ^^ of an inch. 

It will be evident, after this hasty description, that the 
eortex of the cerebellum differs markedly from that of the 
oerebram, in spite of the various structural types of the latter. 
The cells of Purkinje are characteristic of the cerebellum 
alone. The number of layers is less than in the cerebral cortex. 
We are apparently justified in attributing to the cerebel- 
lum some functional attributes of a special type, because 
similar anatomical elements are to be found in no other 
region. The theories which have been advanced respecting 
the functions of this ganglion will be considered later. 

In cross-sections of each fold or lamina of the cerebral cor- 
tex may be seen a central medullary or white portion, resem- 
bling the stem and diverging branches of a twig, with its at- 
tached leaves. This *'^ medullary center^ can be shown to 
consist of bundles of fibers which run parallel with each other 
or interlace, until they turn obliquely into the gray matter of 
the cortex. It is still undecided whether these fibers termi- 
nate in the "granule layer'' of the cortex, becoming joined 
to the axis-cylinder processes of the cells of Purkinje, or by a 
union with the plexus of fine fibers described as existing in 
the outer layer. 

THE CENTRAL WHITE SUBSTANCE OF THE CEREBELLUM. 

The peduncles of the cerebellum have been mentioned in 
the early part of this lecture, but much remains to be said re- 

' The ftrikhig rciemblanoes between thU layer and the granular 8tnita of the olfac- 
iorjf hht bave been commented upon bj Meyncrt. The cells of this layer are regarded by 
Gerlach m oonnectlvo-tiMae elements ; by Ilenle and Merkel as lymphoid elementa ; and 
by Stilling aa mall mvhipolar neire cells. 
17 



229 



^RATK 



specting the probable course of the fibers containe*! in ml 
during their passage through the whiti^ or medallary w 
of the reiebelluiu. The course which they parsoe oai 
of the limits of this gaaglioa will also merit eubeeqa 
attention. 

The fibers of the anperior peduncle can be tmred iln 
entirely into the interior of the ** nucleus dentntum"; 
though a few can be demonstrated to pass aj-oand th«* « 
side of this central mass of giuy matter without entertnj:! 
and some mesial fii)ers can be shown to enter directly intol 
white substance of the venniform process. As was elatedl 
be the case with the corpus striatum and the optic lhAlia 
it is probable that a few of the fibers which apjiarentljr < 
the substance of the nucleus dentatum do not become ; 
with the cells of that body, but simply pass t!irou*xh itioj 
to the cerebellar cortex ; on the other hand, it is eqo 
probable that most of the fibers w^hich enter it become ; 
ated more or less intimately with the cells found within til 
body, and that they are subsequently continued to a peiil 
eral termination in some part of the cortex. The libers wl 
inclose the nucleus dentntum are so matted logether hil( 
network that it is impossible to trace the coarse of eveo ^ 
tinct bundles from their entrance into the cerebelhim to thrir 
termination in the cortex. The course of these fiben IhitNtgfc 
the crus has been described in preceding pages. 

The fibers of the middle peduncle leave the pons to enlir 
the lateral part of the white substance of the cerehellumi 
two main bundles. One is comi>osed of the superior 
verse fibers of the pons ; the other consists of the lower 
verse fibers of the pons mingled with those of the if^rrki 
peduncle of the cerebellum {restiform body of the meduff^ 
The upper bundle passes obliquely downward over the Ion 
and enters the lateral and anterior portions of the medulla 
center of the hemisphere. The lower bundle, after jolni 
with the fibers of the restiform body of the medulla ol 
gata. ttii-ns upward, and radiates into the u[»per part of 
medullary center of the corresponding hemisphere of the 



^Hd^ 



FlBEIiS OF THE CEREBBLLim. 



223 



I 






Kdo: 



bellnra and the upper part nf the vermiform process. Stillmg 
states that the fibers of the restiform body pass, in part, into 
the nucleus dentatum, while the rest curve over the nucleus, 
— the so-called *' semicirt^ular fibers," 

Finally, certain commissural Jibers are described by Stil- 
Ihkg as existing in the cerebellum. These may be divided into 
two sets. The first are analot^ous to the commissural fillers of 
the cerebrum, crossing the mc*dian line and probably joining 
homologous regions of the cerebellar cortex in the two hemi- 
spheres ; the second, analogous to the collateral fibers of the 
cerebnim, connecting one lamina of tlie cortex with another, 
and arching aixjund the fissures between the lamina\ The 

tter set are confined to one hemisphere, and do not cross 
the median line of the cerebellum. The direction of these 
fil>ers is transverse to that oi the ** peduncular^' cerebellar 
fibers. 

It is evident, therefore, that the general arrangement of 
the cerebellar fibers bears a striking resemblance to that of 
the cerebrum ; the nuden^s dentaiuw^ olivary Jorfy, red nu- 
cleus^ and gray mafter of the pons being the analogues of the 
basal ganglia of the cei^ebrum, and the ** radiating,'' *' com- 
missural,** and *' associating systems'* being similar in many 
respects. The cerebellum, like the cerebnim, may be said, 
therefore, to exliibir three so-called ''projection systems" 
of fibers, as follows : 1, The inner projection system, the 
fibers of which sen^e to connect the cortex of the cerebeb 
lum with the nucleus dentatus of the same hemispliere and 
the olivary body, the red nucleus lyf the tegmentum, and the 
anterior gray sulistance of the pons Varolii of the opposite 
side ; 2. The middle projection system, the fibers of which 

innect the enumerated masses of gray matter with the gray 
matter of the cms, pons, and spinal cord ; 8, The outer pro- 
jection system, the tibers of wliich are included in the expan- 
sions of the central tubular gray matter to the periphery of 
the body by means of the spinal nerves. 

The following diagram ^\ill help to make certain points 
clear regarding the intimate structure of the cerebellum and 




THE BRAIN. 



its connections i;vith adjoimng parts. It is, of connie, pOR^ I 
schematic, but, it used in connection with actual repwMfi^ 



OnURA CEftCBUt 



rN, 



Q. H* P. 



4.S 



-^-m. 



FtG. 48. — ^il diq^rom ^mgntd h^ iht tnffhor to Uiuatmie iht witruma mtU ^ Atm \ 
prited mthin the ctrc6flh>^\fAnat ni)§tem, (llodilicd frotii Roea.) 

a ii.« cru?tA eniritj ; t. f. o., te^cntum cruris; a. s., iqueduei of 8vlrlu9 stirroii&d^ ^ ^ 
tubular (rmy matter ; b. m.^ isub^Untia tiign ; r. n., rt*d oucleus of tli# 
G. M. P,^ anterior gray matter of the f>on« ; c. c, cer«bclla eorten ; %. i>,^ huidrQi i_ 
turn ; o. a,, olivary body ; n. a., elavate nucleus ; T. K, trianguUr tiudeus ; ii,c,t I 
of the '* direct cerebellar tract '* of the t^piual c<Mii ; v, it, x.» fitH*r» of il»« **pOil 
Tf-KJt * zone *' of the aatne; O*, fibers of the "cohinin of Ctotl**; I, ct 
lar iiben! ; % tiberB from ttio re<l uueleus of the togtuciittiiti to the d)fstk\mim l. 
the cerehellum ; S, fibers from the n?d nucleus to the ccrrbeJUr cortex : 4, S^B 
from the cerebellar cortex lo the denute nucleus ; &^ fibers from the vlentste vaiMi 
to the olivary ImkIv of the op(iosite side ; 6, fiberF from iho eervlic?lliir cvirtrx to iW 
olivary body of the oppo^te fride; 7, fibers from the cerebellar cortex Co the aafm* 
P'ay nucleu.o of the poos of the opposite ^ide ; 8, fiber? of the flircct eerr).. 
9, fibers oonnectin^ the claTate nticletis and the olivary body of the «siiiL.r 
fibers conneetinf; the triangular nucleus and the olivary body of the 9mn%v *>j^\ i*, 
fibers pad*4ing from the olivar>' body to the horns of the spinal gr«y villff: 
12^ fibers paiisttng from the anterior ^ay rontter of the potis to tlu* hortis 0f ipiMi 
gray matter; 13, fibers passing from the red nucleus of the tcj^ientutrt tQ ih^ aal» 
rior horns of the spinal ^ray matter; 14, fibers cscapini? frofn the ^pftial mrd rhn^ 
the antei-ior root of a spinal nerve ; IB, fibers of the post* i -^f^ 

entering at the posterior horn of the 5pinal prny matter. rrf rf 

the spinal cord, near to 15, indicate the relative poeitioo ot mv mhcreni tractt villi 
which they am eonnecioil a, a, a. represent fibers which sre deftlanl io 
fHlfeTcnt convi>]utions of the ccrcbcUftf cortex {^fihra propnm). 



immW^ 



FIBERS OF THE CEREBELLUM. 225 

's ttons of the parts, it will prove of great value in comprehend - 
^ ing many statements which are to follow. In this diagram 
the shaded parts represent collections of gray matter ; the 
*]mes indicate the direction and extent of individual sets of 
nerve fibers which are in direct communication with the 
shaded masses. 

The arrangement of the middle projection system of fibers 
]>ertaining to the cerebello-spinal apparatus is less definitely 
settled than that of the cerebro-spinal. It is probable, how- 
ever, that the cerebellum receives afferent sets of fibers from 
tbe spinal cord, and gives off also certain efferent sets of 
fibers, which are brought into more or less direct communica- 
tion with the motor tracts of the crura, pons Varolii', medulla, 
and spinal cord. 

The AFFERENT FIBERS of the Cerebellum probably reach 
that ganglion through the following channels (Pig. 48) : 

1. By means of the columns of Ooll (a), which terminate 
in the soK?aUed " clavate nucleus^ (c. n.). 

2. By means of the columns of Burdach or the posterior 
root zone of the spinal cord (p. r. z.), which seems to be struct- 
urally related with the so-called ^'triangular nucleus '^^ 
(t. n.). 

8. By means of fibers which connect the triangular and 
davate nuclei with the ^"^ olivary body'^^ of the corresponding 
side of the medulla oblongata (9 and 10). 

4. By means of the ''^ direct cerebellar tract ^^ of fibers 
(d. c. T.) which is found within the lateral column of the 
spinal cord near to the extremity of the posterior horn of the 
spinal gray matter. 

6. By means of fibers connected with the auditory and 
possibly with the sensory root of the ^fth cranial nerves. 
The auditory fibers are probably associated chiefly with the 
corpus dentatum and the nucleus fastigii. It is stated that 
they decussate either in the medulla or cerebellum. If so, 
they pass through the auditory nucleus before entering the 
cerebellum. The apparatus of hearing performs an important 
part in equilibration. 



THE BBAIN. 



The EFFERENT FiBEES of the cerebeUum ' are 
comprised within the following fasGieiiU : 

1. Bundle3 o£ libers which connect the den/a/^ nue 
and the cerebellar cortex with the corpus striatum or V^ 
thitlamus by means of the '* processus cerebelli ad cer 
This bundle is also in intimate relation with the *^red m 
of the tegmentum,'' and probably is structurally relate 
some of the nerve cells found in that nucleus (2 in Fi| 
Luys believes that the corpus striatum is charged^ when il 
nervous force becomes exhausted, by means of this pnx«»l 
the cerebellum. If this be the case, the cerebellum 
some influeuee upon the impulses emitted from the 
hemispheres ; because many such impulses are pr 
modified within the coi-pora striata before they are 
mitted to the more distant parts of the nervous appanitusttl 
gxiiy matter of the spinal cord, and the spinal nurves). 
probable relations of cerebral and cerebellar iafluenoes jy 
muscles will be discussed later, 

2, Fibers which probably connect the red nucleus 
fef/menfum with the anterior bonus of the spinal gray matter 
(13 in Fig. 48). 

3, Fibers which probably connect the atirarp bodies d 
the medulla oblongata with the anterior horns of the Bpiml 
gmy matter (11 in Fig. 48). 

4. Fibers which connect the anteriar gray su-bstance ^ 
the 270718 Varolii with the anterior horns of the spinal gmy 
matter (12 in Fig. 48), 

Fix>m the imperfections of our present knowledge, mi 
that is stated here I'egarding the exact course of the aflFe 
and efferent impulses of the cerebellum must be somewbal 
coJijecturaL The results of experimental physiology and 
pathological research are not, and can not well be, of a pt»« 
tive character. Many conflicting theories have been at di 

Mf the brain b<» considered as a whole, fibers pcuaing from the oetiftbetltim to i 
oerebntm bj moaoA of the superior and middle pcdanelcft, %a well m thcHia pftsainf \ 
the tuherctilar quatlHj^ernma, by means of the valve of Victi^tteiii, maj be 
afffrmi Jiben. Spitzka denies the exi^teooe of tffffrtnt ocrebellar fibera (oQtaidt of iht 
tuperior and middle p«duucle0). 



PEDUNCLES OF THE CEREBELLUM. 



22; 



prent times advanced regarding the funcdonal attributes of 
til is ganglion. These will he considered when the anatomical 
lata have been moi^ fully presented- 

Processus cerebelli ad cerebrum (processus e cerebello ad 

nsUs^ superior peduncle 0/ cerebellum).— In connection with 

irevious topics, chiefly in those pages which treat of tlie corpus 

Itriutum and the optic thalamus, the relation of the cere- 

Bllura uith the medullary portion of the cerebrum by means 

)f special filjem has been mentioned. The special group of 

wliicli compose the processus cerel>elli ad eembrum ap- 

eiir to start anteriorly from among the radiating fibers of the 

[jrebnim and are forced apart, in the region of the crns, 

[>ve the corpora quadrigemina, by the introduction of a 

mass of gray matter^ characterized by nerve cells and 

luhu* material^ the so-called ''red nucleus qfthe tegmen- 



/ r 



}.*^A cr^Ur diagram dmipm! % thf nnthnr to WtmtraU tht tkrt pain of ptitm- 

ctrm o/thr ftreffritum, 

Tbotv of 0D€ nldo ouljr are shown. 

fum,^* In the region of the lower half of the superior corpus 
^igeminum this tract appears as a simple bundle of fibers, 
rhicb ai*e not destitute of nerve cells, luit whose clrcumfer- 
i» much less than in tlip reiri*>n of the red nucleus. The 



328 



THE BRAtN. 



nerve cells of this bundle ai^ of extreme size, and appevi 
be arranged pamlkl with the vessels of that r»* ' ^e| 

than with the nerve fibers. In some cases they bei. . ^ ^: lii I 
angles of the branches of the arteries, and send our long ff*- 
longations that run longitudinally along and probaNf a 
their walls (Meyiiert). Even in the *'red nucleus^ lUsir 
rangement may be demonstmted. The presence of nervecdk I 
within this tract does not cease until after its decnssarion oJ I 
its escape from the corpus quadrigeminmn. It yet renum | 
to be demonstrated whether the crural portion of tfaapo-l 
cessus cerebelli ad cerebrum is the only seat of a peripltffil ' 
termination of nerve-cell processes in the walls of capiUihti? 
In the midst of the c^nti-al organ. 

If successive cross-sections of the region oecnpted bf tUi| 
tract be studied, it will be seen tliat the processus dmbtfij 
ad cerebrum of either side approaches the median line, tadJ 
that the fibers eventually decussate. The region occupied bfl 
these decussating fibers lies between the ^^posteriar lofigituih 
nal /asciculus-^ RTid the ^'^strattim Umniac/^^^ the remaiiiiif 
bundles of spinal fibers which enter the tegmentum hafiJil 
been crowded away by them. After their decussation, tb« 
fibers pass outward until they reach the inner surface of tk# 
inferior lamina of the lemniscus, which forms a sort of prv-j 
tective cover for them, Meynert has compared the outlii 
the two processes to the form of a horseshoe^ whose o| 
is directed backward. This opening represents an area whicb ' 
embraces those fibers of the *' tegmentum cruris •' directly pw- 
longed from the spinal cord ; bounded by the stratum Jem* 
nisei and the posterior longitudinal fasciculus. The dt'cm* 
sating fibers of the cerebellar tract fonie their way among 
fibers of the tegmentum cruris to reach their lateral positioa; 
hence, cross-sections made at different altitudes show ev^r- 
varying relations between these fibers and those of the teg- 
mentum. Stilling and Arnold, who have made a special study 
of the course of the Abel's of the processus cerebelli ad ren^^ 
brum, differ as to the completeness of the decussation, the] 
latter denying that all the fibers cross the median line, Mey- 1 




YALVE OF YIEUSSEm, 



229 



confirms the view, originally advanced by Stilling, that 
le decussation is complete. 

^ After the decussation of its fibers, each processus disen* 
itself, both superiorly and externally, from the fibers 
^f the tegnientum cruris in which it was imbedded. Oppo- 
ito to the point of greatest convexity of the pons Varolii, it 
pomes uncovered by the inferior himina of the lemniscus, 
itcTinits course it becomes buried in the white substunce 
^t the cerebellum, and finds an ultimate connection with the 
^Bncleus dentatus," the central mass of gray matter within 
ie cerebellar hemisphere. 

When we examine the fourth rentride, the exposed por- 
ion of this tract will be seen to constitute the lateml bound- 
-walls of that cavity (processus e cerebello ad testes) ; with 
le so-called ** valve of Vienssens'* (celum medullar f/ a n^e- 
"ius) inclosed between them. The latter formation deserves 
cial notice in this connection. 

The processus cerebelli ad cerebrum itself is by no means 
tree from admixture of foreign elements during its passage 
sm the cei'ebrum to the cerebellum, the details of which I 
Mre just given. At the level of origin of the fifth cranial 
re (trigeminus) fil>ers from the cerebellum apparently pass- 
ig to the greater root of that nerve can be demonstrated as 
ciruli which in part cover it and in part traverse it. It 
in also traversed, at a lower plane, by fasciculi destined to 
belong to the eighth cninial nerve (auditory), 

Valte qf Vieussens,--hi this commissural band (the me- 
lallary velum) three different systems of fibers lie inter- 
^woven : L The great mass of its substance is composed of 
bundled of fibers derived from the frenulum, 2. The decus- 
sating fibers of the fourth cranial nerve (trochlearis), wliicli 
are grouped at the anterior extremity of the valve into bun* 
d]m of exti*cme thickness, are intertwined transversely with 
the fasciculi of the frenulum, 3. Certain longitudinal fibers 
may be demonstrated which can be traced to the superior 
verm S form pr>cess of the cerebelhim. The course of these 
They decussate befoi*e leaving the suj^rior 



THE BRMK, 



vermiform process ; they then traverse the valve of Vie 
almost to the Itiwer border of the eorpass qij:i ' ' 
this point thej iluuble upon themselves, il. _, . 
whose convexity looks upward ; finally, they join the m 
hxmina of the lemniscus nt its posterior bundle, aod pajs5< 
wartl with the latter, in the posterior division of the 
Vai'olii, to the spinal cord. 

Processus cerehelU ad pontem {middle peduncle f^t 
bdlwm). — When the general ai'chitectui'e of the oewhtii- 
nal axis was under considenition, the mlation of the^ 
liim to certain fibers which helped to form the *^ ba^ 
of Meynert (rrusta cruris) was touched upon, as uti nmtn 
cfd explanation of the fact that the number of tiberHc^l 
middle projection system siiflfered an apparent decrease Ai 
ing their i)assagf» through the pons Varolii. It wa^ 
stated that some of the efferent fibers of the cerebrmn 
ably left the direct tract of the projection system wjj] 
the region of the pons, and passed to the cerebellum, 
points pertaining to the physiological imi>ortanee of thfl 
ibers were also mentioned in connection with my descriptiq 

the corpus striatum. It has, moreover, been stated in 
vious lectures, that the region of the pons contained 
transrerse Jihers connected \nt\\ the cerebellum, which xbM^ 
laced \^nth the fibers of the cerebral projection tiTiets* and 
were probably more or less intimately a^ociated with lint, 
nodal masses of gray matter found in that region. Some i 
these fibers are unquestionably commissuiid in c^ 
serving to unite homologous regions of the cerebelL,* 
spheres ; others probably serve to unite the hemi.sphen« 
the cerebellum with the gray matter of the pons of the op] 
site side. In man the pons is long, because the crustii eruriT 
is developed in proportion to the size of the cerebral lobes; 
in animals it becomes shorter in proportion to the deeraoiift ia 
siae of the cerebrum. The interlacement of the fibere of the 
projection system with those of the '* processus eerehtslli 
pontem " occupies the region of the pons and the upper 
of the medulla (Meynert). It is somewhat curious to o\ 




THE RESTIFORM BODY. 231 

that the lateral regions of the cerebellum keep pace in their 
development with the cerebral lobes, and the ^^ nucleus den- 
tatus^^ of the cerebellum is developed in direct proportion to 
that of the olivary bodies of the medulla oblongata. 

Cross sections of the region of the pons reveal the fact 
that the transverse fibers of the processus cerebelli ad pontem 
may be divided into three sets, as foUows : 1, a superficial 
layer ; 2, fibers which interlace with longitudinal fibers escaj)- 
Ing from the eras ; 3, a deep-seated layer. The superficial 
and deep layers appear to be perfectly independent of any 
association with the fibers which belong to the middle projec- 
tion system of the cerebrum (those of the crusta and tegmen- 
tam cruris). Meynert, however, brings forward certain rea- 
sons, based upon a minute study of the general relations of 
these layers, which apparently lend support to the view that 
the fibers of these strata are in communication with nerve- 
oells embedded in the pons, that certain crural fibers are like- 
wise joined to these cells, and that the two sets of fibers are 
thus brought into communication with each other. He states 
his conclusion as follows : 

"Each fasciculus of the basis cruris cerebri that termi- 
nates in either side of the anterior division of the i)ons is rep- 
resented in the cerebellar hemisphere of th£ opposite side by 
two /ascicuUj one of which runs with the superficial, the 
other with the deep stratum of the transverse system of fibers 
from the point of their connection with the crural fasciculus 
into the processus cerebelli ad pontem of the opposite side." 

Processus cerebelli ad medvllam {jestiform hody^ irtferior 
peduncle of the cerebellum). — A complete description of this 
important bundle properly belongs to a subsequent lecture, 
which shall treat of the architecture of the medulla oblon- 
gata* It is a round and prominent cord, which passes direct- 
ly into the corresponding hemisphere of the cerebellum. The 
fibers of the direct cerebellar tract and the arched fibers of 
the medulla oblongata can positively be traced through it to 
the substance of the cerebellum. The distribution of some 
other bundles found within it is still unsettled. The fibers 



S32 



THE BRAIN^, 



of the restiform body probably t-erminate either in tliempl 
dentatutn, the cortex of the posterior snrfaca of thebeBJ 
sphere, or the centml gray matter of the worm. 

RELATIONS OF THE CEBEBELLCM TO CBAXIAL ITXRTBl 

At various times articles have appeared which twrf I 
show that the libers of origin of some of the cranial m^ 
can be traced to the cerebellum. When a positive 
stration of the statements made by some of the later i 
mists can be furnished, mtich light will be shed upon 
functions of this ganglion. There seems to be every 
at present, to believe that the auditory n^ri^e can be i 
to the cerebelliim after its fibers have passed through the \ 
ditory nucleus ; and the number of such fibers appearstitl 
in excess of those actually comprised within the nerve 
In this respect a strong analogy is presented between tbei 
ditory fibers and those of the coronary radlata of the 
brum, which are themselves more numerous than tho^ofl 
crus, although they appear to be in direct continuity will' 
them (as was stated when the basal ganglia of the oefel 
were under consideration). The opinion advanced by Spil 
ka, that the fibers of the sensory root of the triffeminnsf^ 
be also traced to the cei'ebellum, lacks positive confirmBlidi 
as yet ; and the same remark might apply with equa] joieIiic 
to the views of those observers who believe that the 
fourth^ and tenth cranial nert>es have a direct 
with that ganglion. There are physiological experinienffT 
record which seem to sustain all of these views ; as well as oll^ 
ers which combat them. These will be explained later The 
proof, however, that fibera of the nerves mentioned ran 
actually demonstrated within the substance of the cerebelliid 
cannot, to my mind, be considered as final, although son 
neurologists are inclining more strongly of late toward that 
belief. 

THE FUNCTIONS OF THE CEBEBELLUH. 

Prom the date of Flourens's first experiments upon 
cerebellum of animals down to the present time, neither i 



FUNCTIONS OF THE CEREBELLUM. 



233 






in 



sibility nor marked excitability seems to have been demon- 
strated as attributes of this ganglion. Animals which have 
suffered extreme mutilation of the cerebellum experience no 
apparent pain, nor does direct irritation of that ganglion re- 
sult in pain or convulsive movements. The opinion that the 
cerebellum is incapable of direct stimulation, which is still 
held by some physiologists, seems to be confuted, however, 
by the experiments uf Budge, who observed that movements 
of the testicle and vas deferens occurred in the male, and of 
the horn of the uterus and the Fallopian tubes in the female, 
W'hen dimct irritation of the cerebellum was emi>loyed. The 
same observer x*i"<*duced movements in the stomach and 
oesophagus by means of cerebellar stimulation. 

The widest differences in opinion exist among physiolo- 
ts and neurologists regarding the functions of this gan- 

lion, since the most positive and direct results of experi- 
mentation upon animals are ai>parently contradicted by 
pathological observations upon the human subject, Tliere is 
one conclusion, however, in which most physiological observ- 
ers, since the date of Fhairens's oiiginal experiments, concur, 

iat,, that the cerebellum, in some way, influences to a marked 
degree the coord umtion of museular movemerds. This is 
very apparent in birds deprived of the cerebellum in wdiole or 
part ; since the power of performing delinite and regular 
ts of locomotion is lost, although the animal is not para- 
lyzed. If laid upon the back the bird cannot recover itself, 
in spite of exhausting efforts to do so. If placed upon the 

eet it executes sudden and disordered movements, and show^s 
agitation which is in marked contrast to the stupor which 
follows a removal of the cerebral lobes ; it can still see and 
hear, feel pain, exhibit evidences of volition in its endeavors 
to avoid a threatening blow, and apparently it possesses nor- 
mal intellectual faculties. life is not particularly endan- 
gered by these experiments, as some of Flourens's birds lived 
several months; although se%^ere hiemorrhage and injury to 
the medulla may sometimes occur in perfonning them. If 
only portions of the cerebellum are removed, the animal ap- 




234 



TSE BRAiy^. 



pears to slowly regain its i>ower of coordiuation of mo^ri?] 
Tnorement; this fact may tend to explain the n* ^ ^ 
marked symptoms in the human subject, in 8pite of 
lesions. 

When Andral published a collection of ninety-thiw 
in which well-marked lesions of the eerebellnm w* ^ ' 
after death, and announced that only one snsiauie':. 
that the cerebellum governed coordination of mm 
physiologists were startled and made to doubt the 
ness of their own conclusions. These cases are» he 
carefully analyzed by Flint, who enters into a lei 
ment to prove that the oases cited do not warrant the coirJi 
sion of their compiler. Nothnagel published in 1B78 
re^snlts of his analj^sis of more than two hundred and fiJ 
cases of cerebellar disease. He is inclined to admit the 
ence of cerebellar ataxia (which he describes as a perrcisiai 
of equilibrium resembling alcoholic in toxica f ion) an chai^ 
teristic of cerebellar disea5>e ; but he thinlcs that the nnperi^if 
mrmiform process is especially liable to produce il, if cxt«5 
sively affected. In the majority of instances the npi>er 
tremities remain free from incoordination, Snbjecta in wh 
cei*ebellar ataxia is well marked stand, aa a ml^^ with tbfir 
feet well apart, in order, as it were, to increase their base d 
support ; they sway from side to side and titubate ; the t/cm 
are seen to be in active motion if the patient stands hti«-, 
footed ; in walking, the body sways and the heel and halli 
the foot are brought into contact with the ground irnegii 
the ataxic symptoms may and may not be increased bj 
ing the eyes ; in the recumbent posture all these ataxic 
festations entirely disappear. 

The tentorium cerebelli, which senses to separau^ itiei 
bellum from the posterior cerebral lobes, and which in 
animals is a partition of bone, ajipears to have a clinical bctr 
ing upon the development of lesions of the cerebellnm^ 
it seems to favor their g^rowth in a forward and downwa 
direction. It is important for you to bear this in mind whe 
the effects of focal lesions of this ganglion are under oofir 



STMPTOJfS OF CEREBELLAR LESIOJ^S. 



236 






sideration ; as well as the fact that an experimental or patho- 
jgiral lesion seldom, if ever, involves all the numerous nerve- 
icts and centers which exist within this ganglion, and have 
ditTerent peripheral connections. 

b By recalling the important connections of the cerebellum 

with other parts of the brain and tlie spinal nerve-tracts, l>y 

jine-ans of its three crura, and bearing in mind also that the 

rd, fourth, fifth, acoustic, and jmeiimogastric nerves may 

ibly have dii*eet sources of origin within its substance (the 

proof of a relation with all of which, however, is still some- 

rhat unsatisfactory '), you can readily understand that the 

lymptomatology of cerebellar lesions must, of necessity, be 

Bculiarly involved and complex. The important organs 

rhich underlie the cerebelhim (the corpom quadrigemiDa, the 

tegmentum cruris, and the medulhi ol>lorigata) are lial>le, fur- 

_therraore, to be simultaneously affected, either by pressure or 

le extension of the disease to these parts. Within the first 

of these we prol>ably have centers which govern the move- 

aents of the eyeball (Adamuck) ; in the second, a vaso-motor 

^nter, and possildy one which presides over convulsive move* 

meats, (?) are believed by some authorities to e^rist ; in the 

third we find the olivary bodies, which are connected with the 

cerebellum, and the various nuclei of origin of important 

.cranial nerves. 

We are apparently justified, on anatomical grounds, in 
attributing the disturbances of vision w^hich are so often ob- 

t^rved in connection with lesirmsof the cerf]!bellum to ju'cssure 
pon the geniculate bodies, the corpora quadrigemina, or the 
bers or nuclei of origin of the third, fourth, or sixth nerves. 
On similar grounds, the attacks of nausea^ vomitinff^ cardiac 

Kistiirhavces^ and sufJfJen death sometimes encountered may 
e attributed to the pressure of cerebellar lesions upon the 
uclei of origin of the vagus nerve wathin the floor of the 
fourth ventricle, resulting in either irritation or complete 
paralysivS of that nerve* The coJivulsim attacks^ which are 

' The eonnectioQ of the ttuditortf nerve with the cerebeUain ia now quite geuerftllj 



ted b/ neurulogistd- 



of 



w 




236 



THE BE AFX. 



occasionally observed in connectiou with cerebellar IsimX 
may perhiii)s be explained by pressure upon the coontoj 
center of the tegmentum cruris ; and the develapmeit 
hemiplegia of an imperfect type, or of general poroi^l 
both of which have been reported as ocouning from ^sA 
bellar disease, may be explained by a similar effect ujjoftJ 
direct motor tract of the cembral projectioD system. 

In direct antagonism to the results of Plourf iis*s esp 
ments, lesions of the cerebellum of the human race seOTi 
be often associated mth pain, which predominates in the i 
cipital region. In fact, the diagnosis of cerebellar A\&mit i 
made chiefly on the predominant occipitiil ])ain (1 
Sequard, Seguin, and others), with titubation and other 
culiarities observed during the erect attitude of the 
Exclusion of disease in adjoining regions mu8t» bcii 
always be made by the absence of symptoms befom 
a positive diagnosis, because occipital pain and tatnbali 
may both be often w^anting, and the so-calle<l *' ataxic 
tums," when present, do not exist in the marked degree* 
moflly met with in posterior spinal sclerosis. It is anoii 
mon to finA true ataxic jerking; and choreic moTementsj 
tremor are usually absent. The want of harmony betwdfi 
antagonistic groups of muscles is also w^anting:. 

An attempt has been made to connect the cerebellum irilk 
the generative function, but physiological experiment bii 
apparently demonstrated its fallacy. A rooster, in whom the 
cerebellum had been removed, attempted to mount a bdr 
eight months afterward, and failed appai-ently only on 
count of the lack of power to coordinate his muscles 
reus). There seems to l>e no well -authenticated ii 
where the sexual instinct has been destroyed in ani 
removal of the cerebellum. Leu ret found that the cerel 
was even larger in geldings than in stallions or mares. Aroc 
the nnmerotis cases of disease of this ganglion to which «• 
have referred, some suffered from a marked excitation of the 
sexual apparatus, wliile others had a welhmarked utrophy of 
the genital organs and impotency. There are many phydo^ 



SYMPTOMS OF CEREBELLAR LESIONS, 



237 



il as well as pathological facts which tend to refute the 

itlea that the cerebellum is the seat of sexual instinct, and to 

^Jocate it in the lumbar regioo of the spinal conl ; still it can- 

^Bot be denied that numerous cases, on the other hand, seera 

^■o point to some connection between the cerebellum and that 

center, or the organs of generation, in the human subject. 

When the corpus striatum was discussed, it was stated that 
the superior peduncles of the cerebelhim could perhaps be 
traced to the so-called ■' yellow nucleus'- of the caudate por- 
■tion of that ganglion. Luys considers that by means of these 
^^bers the cerebellum is thus enabled to constantly reenforce 
the cells of the corpus striatum when tliey Jjecume exliaustetl, 
thus enabling them to exert their modifying elTects upon all 
■|he motor impulses arising in the cerebi'al cortex which are 
^forced to pass through them, as well as to manifest a peculiar 
automatism which the cells of the basal ganglia seem to pos- 
sess. This theory of Luys does not differ markedly from rhat 
advanced by Mitchell, viz., that the cerebelhim serves as a 
storehouse of nerv^e force, which nuiy be drawn by means of 
any of its peduncles when emergencies arise to demand it. 
Some interesting i^hysiological experiments have been made, 
which seem to point to some intimate association between the 
?rebf^llum and the basal ganglia. We know that section of 
le middle peduncle of the cerebellum almost invariably gives 
to a peculiar '' forced movement,'* the animal rolling nip- 
idly mund its own longitudinal axis, the rotation being com- 
monly toward the side operated upon.* This is accompanied 
^y a i)eculiar dancing and oscillation (jf the eyeballs, termed 
^.* nystagmus." Now, Purkinje observed long ago that elec- 
tic cuiTents sent through the head from ear to ear produced 
le same movements of the eyeballs, and a tendency toward 
le forced movement of rotatitm. The patient leans toward 
le antnle, and objects spin before the eyes in the direction of 
le electric current. When the current is broken the objects 
evolve in an opposite direction, and the patient leans toward 
the cathode, Hitzig has sho\^Ti that neither the vertigo nor 

^ Becbtercw tuui l&telj shown that secttou of Ihc olivari^ bodia has Ihe mme effect. 
18 





23S 



THE BRAIN. 



the raoYements of the patient's body depend apoQ th« < 
perceived by vision, since the same phenomena were ^i 
in blind suljjects and in those whu«e eyes were clcisied- 
found also that vertigo could be excited in this fray wii 
current too feeble to excite ocnlar movement*. 

These remarkable experiments have been iiBed by < 
authors as confirmatory evidence of the three fulluwilig ] 
sitions : 1, That the symptoms pixxluoed indicated an 
lectronic and catelectronic state of the respective aiwlto 
nerves ; 2. That the cerebellar structures were catlcd 
action by the current ; 3. That i>arts of the cerebram 
affected by the current 

The experiments of Cyon afforded ground for the 
proposition, since he found that, when the seniieircular < 
of the ear were tlivided, peculiar ''forced movements '^i 
loss of coordination were produced, The symptoms noti 
in auditory vertigo (MSnidre's disease) are strongly in 
with these experiments, since slight defects in hearing ; 
accompanied in some instances by alarming vertigo, 
ing, and unconsciousness. 

The second proposition seems improbable, because the \ 
of the electrodes would appear to be too far removed fromdir 
cerebellum to directly affect it. 

The third proiiosition is based upon the situation of 
electrodes and the fact that the electric current may b«siip^ 
I>o8ed to pass in tbe most direct line through the eembral si^ 
mce. It is possible that the artificial current is suffletendx 
rong to arrest in its passage the cerebellar current wl 
constantly flows into the cells of the caudate nueleu!^ of 
corpus striatum, and that the symptoms of vertigo anil infl 
ordination are to be thus explained, 

From a standpoint of our i>resent knowletlge, the 
lum must be considered as the *' terra incognita " of the br 
The clinical evidence is discc*rdant. The anatomical conneD- 
tionsof the cerebellum with other parts of the nervous systi 
are remarkable, and their minute structure is, as yet, it 
fectly understood. The region overlapped by the eeret 



SYMPTOMS OF CEREBELLAR DJSTURBANCK 



m 



lEterspersed with important collections of gray matter 
l^bich net a.s nuclei of (»rigin for important nerve tracts, so 
l^iat all experiments made upon the cerebellum itself, or ita 
Hpduncles, are liable to cause injury t*:* some of the neighbor- 
I ing parts, and thus to yield results which are puzzling and 
, unreliable. Conjecture inevitably forms an important element 
aJl of the theories advanced respecting the functions r)f the 
inglion itself, or of certain of its parts. Nothnagel claims 
have demonstrated that meclianical stimulation of the sur- 
of the cerebellum will give rise to muscular movement 
ithout signs of pain being perceived. He found that these 
Movements developed sluwly, appearing first on the side opei^ 
Qpon, and then ceasing, only to appear upon the opposite 
le. He states that he has demonstrated that the fifth, facial, 
id hypoglossiil ner\^es, a« well aa nerves disti'ibuted to the 
ink and extremities, can be thus called into action. The 
ime observer concludes that destr action of the commtJssural 
bent of the cjerebellum alone produces Incoordination of 
"fhovement. Hitzig and Ferrier believe .that injuries to the 
iteral lobe produce the same varieties of ''forced move- 
lent^^'as are noticed after section of the middle peduncle, 
louit^ns observed that injuries to the anterior or posterior 
irt^s of the median process caused animals to fall forwaixl or 
ickward respectively, and his views have been confirmed by 
thers. Perrier found that stimulation of the cerebellar cor- 
by the iuterruy>ted electric con-ent produced in monkeys^ 
Its, and dogs movements of the eyeballs, with associated 
nvements of the head, limbs, and pupils. Adamuck pro- 
duced the same effects, however, by stimulating tlie corpora 
^nadrigemina. Hitzig refutes the view that Ferrier's results 
^redne to an escape of the current, by claiming to have pn> 
Pnced similar effects by mechaniiud irritation of the cortex* 
rkhard luus brought forward facts which tend to show that 
certain parts of the cerebellum lesions tend to produce dia- 
or dimple hydruria, thus resembling the effects of irri- 
m of the medulla in the regioa of the floor of the fonrth 




.^^ 



240 



THE BBAIJf. 



In tlie face of this conflicting mass of experimental r^ 
dence, I mention now one of thw mosi Xilausible nml iiurr»\ 
theories inspecting the rehition of the cerel>elliiiu an^j '*| 
brum to mnscular contraction, which has be<^n adviK:atM^| 
Spencer and sustained by Haghlings-Jackson, ]ic66i» 
others. It is believed by these anthore that all cofili»9tm\ 
tonic museuZar emitractiofi is governed by the r- - i-i 
and the alternate or clonic museular eonira^ 
cerebrum, in so far as they are requii-ed to maintain a !« 
or produce a change in attitude. In aU effon^s to m 
attitude (one assumed as the result of some cerebmi miiP-j 
sion received), the cerebellnm holds the miisetilar apf 
in its proper state of tonicity ; but when the utlitode is u»l 
changed, for any possible reiison of which the cer^bmni 
conscious, the proper muscles are relaxed and cithers ihr 
into a state of contmctiun by means of the higher 
The body is then intrusted to the influence of the cewl 
if the attitude is to be again maintained, Thii.^ it is 
gested that the cerebellum be considered as capable nf aiilJ 
matic action, but still as a subordinate to the cerebrum, 
jiossesses the power of overcoming it in one of two wtj 
First, by increasing the supply of nerve force to i^ertain 
of cells, then under the influence of the ceivbelliim, and Ai 
altering the traction upon muscles; or, second, by tnhibitii; 
or totally ari^sting the cei^bellar influx to the antagooifllk 
sets of musi^Ies* Both are designed, according to thisTkir, 
to act either autonmtically or in unison, but the cej^liellEa 
is the servant of the cerebrum, to do its biddinfj^ whea re- 
quired* 

It will be at once i)erceived that this theory applies to thit 
complex physiological acts of walking; the prolonged 
tenance of any given posture; the transfer of the center 
gravity ; the passive state of grotips of muscles : and manji 
the morbid phenomena observed in muscles, as the result 
impairment of the higher nerve-centers. It will be inipcuasil] 
to discuss all of these conditions in this connection, H« 
lings- Jackson and Russ have covered the more inuM^rfj 



DIAGNOSIS OF CEREBELLAR LESI0K8. 241 

ifK>ints in their works. If we form our views of the physio- 
<;logical functions of the cerebellum purely from the standpoint 
vOf the anatomical connections which that ganglion is known 
,to possess, we cannot but agree with Bechterew in some of the 
.conclusions which he has lately advanced. This author be- 
^lieves that the cerebellum is intimately connected with three 
, oxgans which tend to exert an influence upon equilibrium, as 
follows: First, the semicircular canals^ connected with the 
oigan of hearing ; second, the organ of sights since the move- 
ments of the globe of the eye, and possibly the sense of vision, 
may be traced to a relation with the gray matter in the floor 
of the third ventricle, and subsequently with the cerebellum ; 
third, the olivary gray matter^ which the author thinks is 
probably connected with the organs of tactile sensibility. 

The views of this author have been in part anticipated and 
sastained by Spitzka, who, in an admirable article published 
about two years ago, considered the cerebellum as the center 
where " impressions of touch and position are associated with 
those of time and space," and hence the seat of coordination 
of the most delicate forms of movements ; such as are neces- 
sary, for instance, to the proper adjustment of the drum- 
membrane of the ear for the correct appreciation of sounds, 
the appreciation of time and rhythm, and the finer acts of 
equilibrium. In filling this position, the latter author be- 
lieves that the cerebellum is subordinate to the cerebrum, to 
which it acts as an "informing depot *' for coordination, 
rather than as a distinct center. 

DIAGNOSTIC SYMPTOMS OF LESIONS OF THE CEREBELLUM. 

The functional attributes of this ganglion are as yet im- 
perfectly determined, and the effects of lesions (tumors, 
hiemorrhage, softening, and sclerosis) which involve its dif- 
ferent regions vary with their seat. The following deductions 
are based chiefly ujwn those of Nothnagel, who has devoted 
special attention to diseases of this gtinglion, and those of 
Seguin, who has lately contributed a digest of several cases 
of cerebellar disease : 



t3 



THE BMAI 



Lesions of one of tbe cerebellar hem t spheres ape 
incapable of diagnosis, especially if only one hemiHphm)i| 
involved. 

Lesions of the vermiform process are generally altaillf 
with symptoms of a more decided cliaractep, 

Incodrdlnatloih of moifernent^ an intense vertiffo (idtiittf| 
with that of Menidre*s disease), and a ""' tUubaiing ffoUi 
the more common effects of cerebellar lesions ; but thoenj 
not in themselves pathognomonic of cerebellar dts^i^ 1 
they may be produced by lesions of other parts of th€ ko&| 
The consideration of all the morbid phenomena of eachut 
(both of a positive and negativ'e chamcter) is rpi|iiirv] t 
render the diagnosis certain, 

A staggering gait is especially liable to be devdopri ij 
case the **w<»rm'' uf the cerebellum is directly Involved, <e! 
pressed upon by lesions of adjacent parts. It only exfitij 
when the subject is in the upright posture, and the at 
symptoms rai'ely affect the delicate movements of thet 
gers. 

Gastric crises (chiefly exhibited by persistent nami 
are a diagnostic feature of lesions of the cerebellum in 
cases. When destructive lesions of the cerebellum exiA 
vomiting is less frequently observed than when that gangfifli 
I encroached upon by lesions of other parts. 

Atrophy of the cerebelbmi has been observed to pitsdooi 
imperfections of speech (axarthria). The difficulty secof 
to be confined exclusively to the motor apparatua The 
ory of words is not disturbed* 

Pain ill the occipital region is often present in 
disease. 

The organ ofmsion may be affected. Occasionally, 
eyes may exhibit incoordination of movement and iiynt 
mus; and also the evidences uf choked disk, nml>ly».f»in, 
amaurosis* 

HcBmarrhage into the cerehellum is sometimes assiociate 
with a loss of facial expression., due to a slight paresis, 
patient may also exhibit a tendency to assume one pontic 



TEE PITUITARY BODY, 



243 



and to return to it when moved by the iittendants. Should 
hemiplegia ocrun it indicates that the lesion exerts pressiire- 
eflfects npon the pyramidal tracts, either in the ci^s, pons, or 
mednlla. 

^ Irregularity of the hearVs action, which is sometimes ob- 
?rved in connection with a cerebellar lesion, indicates a 
i*essure upon the cardio-inbibitory center of the medidla. 
Abnormal mental sipftptoms are genemlly absent in con- 
nection \^ith cerebellar lesions. When atrophy of the organ 
Kls present, or when other parts t>f the brain are diseased simub 
"laneously with the cerebellum, mental derangements may be 

observed. 

^k When the middle erttra of the cerebellum (those going to 

the pons) are affected by lesions which create irritation, 

^^otary morements of the body and a lateral dejiectioji of (he 

^K^ad. and eyes may be developed. As a rule, these rotary 

^■novements are toward the healthy side ; but this is not in- 

^■rariably the case, as they sometimes are toward the side upon 

^^hich the lesion is situated. It is a curious fact that most of 

the effects of cerebellar lesions are attributable to a greater or 

lesfi extent. to irritation of the criim. 

Lesions of the superior peduncle of the cerebclhmi are 
liable to induce paralysis of the raott^r-ocnli nerve, as shown 
^^y the development of ptosis, external strabismus, and ilData- 
^non of the pupil. Hemianaesthesia and more or less ataxia 
Hpigr be induce<l by pressure upon the tegmentum and the 
^nllet tract (lemniscus). 



THE PITUTTART BODY. 

lat portion of the bmin which lies in the sella turcica of 
le sphenoid bone is called the pituitary body or the hypo- 
physis cerebri. It was formerly called the pituitary gland, 
luse it was supposed to discharge ''pitaita" into the nos- 

It is diagram matically shown in Fig. 37. 
It 13 a small, reddish mass, which consists of two lubes, of 
which the anterior is the larger and embraces the posterior. 




•B« 



THE BRAjy. 



The anterior labels darker in color than the posi^ri^ir,iiL| 
in the adult, consists of a lar^e number <>f sli ' ' >oix4i 
tnbales or alveoli, which are lined with eja:,. ..;:«, 
times a colloid substance is found \%ithin rhem« If if 
to the posterior lobes in mammals only. 

The posterior lobe is developed as a hollow i>n»j»nii»il 
the portion of the cavity of the embryonic bmiii 
destined to constitute the cavity of the third ver* 
i^emains small and undeveloped in the higher rertelJWli 
hut becomes transformed into on integral part of tbi» 
in the lower vertebrates through the formation nf 
cells and nerv^e fibers within it. Occasionally, the ra^ 
which originally existed in its substance remains nmi 
erated. 

The fnnction of the pituitary body is unknown- 
microscopic structure, the anterior lobe doseJy resemti 
that of the thyroid body. 



THE MEDULLA OBLOJ^GATA ANT) POKS VABOUL 

The medulla oblongata is received anteriorly (veiitTad)b0 
a groove on the basilar process of the occipital bone* and p^ 
teriorly (dorsad) into a fossa between the cei-^lTellar hemi- 
spheres. From its sides, the serenth, eighth, ninths teiulk* 
eleventh, and twelfth cranial nerves escape. 

Its form has been conipai'ed to an "irregnlarly tmncaifed 
cone." It is expanded both laterally and antero-po8terioriT 
at its upper portion, and measui-es about one inch in lengi 
three quarters of an inch in its greatest breadth, and «9lij{hl 
less in its dorso-ventral plane. 

The anterior median fissure of the spinal cord is 
longed upward (cephalad) throughout the whole extent of 
medulla, and terminates (at the junction of the medulla with 
the pons Varolii) in a deep recess, called the ^"^ for amen agctm 
qf Vicq fFAzyr'^ Some of the decussating bundles of due 
pymmids partially interrupt this fissure. 

The jjosterior median fissure of the spinal cord is 





fi\ continued upward (cei)halad) into the medulla, as far ns the 

II Tigle of the fourth ventricle, where the so-called ^'^rcs- 

ty'.*. ,,r bodies'^ diverge. 
I We owe to Stilling, Van der 
Kolk, Turck, Meynert, Clarke, 
ileehnig, Kmuse, Spitzka, Lam-a, 
iLeby, Roller, Starr, and others 
■rho have devoted 8pecial study 
lo the architecture of the me- 
^ dill la. the limited knowledge of 
is complicated piece of mech- 
i«m we now possess?. Witliin 
ganglion we find numerous 
illeetiona of gray matter in ad- 
ition to well-defined nen^e tracts. 
me of these gmy masses aiv 
t)gous to, and i)rohably direct 
ntinuations of, distinct areas of 
e spinal gray substance. On 
e otlier hand, we are forced to 
mit the existence of other nodal 
i, which are structurally in- 
ef)endent of any n*latinnsliip to 
e conl. Some well-defined tracts 
}f nen^e fibers within the cere- 
rum and spinal cord find their 
tod in the gniy masses of the 
lediilla and pons ; ' while other 




U*lVV\i«i% VfcVVli 



' In winni'ctiori with the gffiy ^ub<iUnce of 

tfvw* th^pi Ut<» tt»*w'archi*« uf KUehjilg have 
Hf»hl UfMio th*> ri*UtrT<» dcvelojmu'nt 
1 1 ri<»rvp inu'tn, nnd in ihui wty UcJpwl 
nU'qirft mme polriin in ilUputc ro*p<?cthig 
r dintfibuilon. Till* ftiubor dnif« ihc f«l- 
ti|f condiwion* ; 
1. A imct of ncpTo flb«iii fittii«et frwm the 
tal k»l>c of tho ccrchrurn, through Ihc nnt<v 
,.^. dlvUlon of the Internal aip!9ulf, and tho 
Inner two filth* of the erm cercbn, to I he gray 
nuclei In the •iitero«iMdlAii grmj matt(»r of the 



Jlkm 



FlO. 50. — Anifrior ¥ir*r of the mt* 

I, mfimdibuhim ; 2» lubcr dncreum ; 
^^ c<»r|»«ru (illiicaiillA; 4, ccp«- 
bnii pabim'le ; r*, liilwr nnnii- 
krc; 6, origin of the tiiiddlc 
pediiT!**?e nf th<« «*rrcb*:'t!MTt* ; ?, 
uti' ■ ■ , ■ ■■','- ^ j^^i^ 

t" f 

II, ttrH/orm tf^^fti^ 1 J iiupcr 
extrf*ialiy of tUr ul; 

13, li^aint'dtttiu ^> iti ; 

H, M, diim muter tjf xlix- mfd; 
15, optic trnctA: 10, ditiii''tti of 



tin 

11- 






jil 




. ...ull 


fxi 




rve: 22» 


an 




rvL^ of 


Wn^b*'!^. 21, ^Im 




■ T* 


ul iirnc; Ufi, pN 




; U! ; 


2fl, 'Jrt, spinal ftcL 




jrv , 27, 


wjfiUfipmi nerve; 


2H, 


%%, «0, 


oenricftl ocrve*. 








- J 



THE BK.ii.^ 

nerve tracts begin in these gray masses and are eitbpr jr 
longed to other parts of the bmin, or leave the sfilwtaiK^^j 
the medulla as cranial nerves, possessing various fuiictkifi& 

The term ** medulla oblongata/' as first emplr^jred hi 
Vieussens and Willis, included both the enini cei^ri aij 
the pons Varolii, in addiri(jn to the ganglion, to whic 
term is now restricted by more modern aiithor^i. It b' 
hem to include only the collection of nerre tracts and t^^y^ 
masses situated between the pons and the spinal conL 

The medulhi has been subdivided by Kmiise into ll 
portions, whose limits are as follows: The inferior 
extends from the plane of the first eervicaJ neri^e to thelo 
border of the olive ; the middle poriwn tnelndes that 
(jf the medulla between the upper and lower borders of tk 
olive ; the superior porfiori extends from the tipper borders 
the olive to the plane intersecting the middlei of the flonr * 
the fourth ventricle. Sections of the inferior and middle ] 
tions exhibit the central canal more or less modified* ui 
those of the superior portion show the ventricular Hoor, 

The line of or if fin of the anterior roots of the spinal oerwi 
is not marked by a distinct furrow in the spinal cord ; bolfi 
the medulla a well-marked longitudinal groove (whirh extends 
as far as the lower border of the pons) indicates the dlt^ 
continuation of that line. This groove is t>-ii fi iitv . Kiit<*ratri 



pons. This tract of fibers is apparently prolonged {vdut tniVLiti xt j^im\m 

tUo J literal aud posterior portions of the ccrobcUum ; hencv, the i atkcm <4 (^ 

pons must be regarded as interpolated in a tract fthiuli scrvr<« t" orrvb^Ui* 

with the frontal lobes chiefly, but not exclusively, of the opposed cs. i ^i^ 

2. The postero-median nuclei of the ^rny eub^tance of the pong i-* similarijr i 
with a traet of fibers that join^ the cerebellum with the cortex of the Ci«iiipocit.aaipltiit 
region of the cerebruro> It uctct develops when the ccrebellom la w«iutti^, m^A b 
dothed with myeline until some months after birth. The course? of tbti» tract 
be (1) through the external one fifth of the crus; (2) through Uie tutenial oafi 
along the ba^e of the lenticular nucleus of the corpus striatum ; and» (41 oiiti 
oortex. The late development of these fibers apparently dit^rovtM any ootiaootkn 
twoen them and the sense of hearing or of the tactile senj*e. 

3. The caudate and lenticular nuclei of the corpus striatum are ooniweftcd «ilk fl» 
Ducltti of the gray substance of the pons by meansi of fibci-f^ Ihat |iaMn downwanl ikraifll 
the modian bundlef^ of the cms to the substantia nigra and the t\\u\v\ of the pimK fl0 
Bbers of this tract are oonDGCt«d with the cerebollani. after traTeraing 
masses. 



\f man t» am 




QRAY MATTER OF MEDULLA OBLONGATA. 247 

i\ below the olivary body by transverse fibers ; above this point 
n it separates the olivary body from the pyramid. 
s Out of this groove the roots of the hypoglossal nerve leave 
gif the substance of the medulla ; they may therefore be consid- 
•. ered as analogous to the anterior roots of the spinal nerves 
J' below. This analogy apparently holds good in respect also 
, to the area of gray substance within the medulla from which 
f the roots of this nerve appear to spring ; although Spitzka is 
. led to believe that the gelatinous substance anterior to the 
central canal of the spinal cord is more directly connected 
with its formation. 

The line of oUachmeTd of the posterior or sensory roots 
of the spinal cord is prolonged upon the surface of the medul- 
la as a series of bundles which help to form the spinal acces- 
sory nerve. These are seen to approach the posterior roots of 
the spinal nerves in the cervical region, and to swing into a 
direct line of continuation with them above the level of the 
foramen magnum. At a higher level of the medulla the vagus 
nerve roots spring from the same line, and still higher up the 
roots of the glosso-pharyngeal nerve. Assuming, therefore, 
that these nerves escape from regions in the medulla that are 
analogous to those associated in the cord with the posterior 
roots of the spinal nerves, we are naturally led to infer that 
the fibers of origin of these nerves are probably connected 
with masses of gray substance within the medulla which are 
structurally related to the posterior horns of the spinal gray 
matter. This is apparently the fact, as subsequent pages will 
help to demonstrate. 

The changes which occur during the transition state (in 
which the spinal cord is so altered in its construction as to 
accommodate itself to the requirements of the medulla) may 
be simplified to the mind of some readers by an illustration 
employed by Quain, which I quote. He says : ''The opening 
up of the central canal and separation of the lips of the pos- 
terior median fissure bring the gray matter to the surface of 
the fourth ventricle, while the posterior comua are coinci- 
dently shifted to the side, much in the same way as it would 



Z^"^ 



teifawdai 
of tfe^nil 



. ^^^ ...^^ from the ijosteriar saAil 
\ tke oealrai eaml, and the two htril 
led outward^ so that ifae mde^ of tk 
^ the poeterior sar&ce ol ii 



Tbe azBUomiou paBscracnoQ of ttie meiiuJia and [xioii 
pardeidarlj difleult of ocanpn!li«saiaiL Hiietly li^^can.^lli| 



ff^ ^ 



W 



»/r. 



c^ tvrrm$ndinp parU and Ike appa^Wti OTfj c/aniW imitms. (S>o« a i 

by ibc author.) 

Tbe cmtiiiil nerves Are mdieatcd br ntnaernlfL. 0, ganglion of Gn»i>er; I*« iMXtt TU 
C. cerebellum ; F, flocciilua ; II, lifpo|ihe$b cerebri, or ibe {lituitAry bodv, 
WMcb two rouuded ciiiiotitice;*, tbe cor{>or» albk-anttA, jij« sgc'D. 

fibers which compose tlie motor and sensory trurts of tbej 
oerebrum are more or less intorminpled with ma^s^es of gniy' 
matter (some of which have not l>een as yet referred to), and 
greatly aUered in their relative positions to each other wlwaj 
compared with those of the ciiis cerebri above or the spinal 
cord l)elow. 



GRAY MATTER OF MEDULLA OBLONGATA. * 249 

31 ' It will facilitate description to consider separately the 
;j'f;ray and the white matter of the medulla and pons. 

3: 

j^. THE GRAY MATTER. 

The gray matter of the medulla and pons is best compre- 
f bended by tracing from below upward the successive changes 
r which the gra,y matter of the spinal cord undergoes from the 
ix>int where the crossing of the libers of the cerebral motor 
tract (Fig. 7) occurs throughout the entire extent of the me- 
dulla and pons. This subject naturally divides itself into the 
following heads : 

(1) A hasty survey of the architecture of the spinal cord 
at its junction with the medulla oblongata, noting its columns 
and the arrangement of its gray substance. 

(2) The gray substance of the medulla at its lowest jmrt 
contrasted with that of the spinal cord. 

(3) The nuclei of origin of the cranial nerve roots. 

(4) The method of continuation of the anterior horns of 
the cord upward. 

(5) The continuation upward of the posterior horns of the 
cord. 

(6) The continuation upward of the central gray column 
and that of Clarke, which becomes apparently represented in 
the lower planes of the medulla. 

(7) The accessory nuclei, which are developed with the 
medulla and pons. 

(8) The superadded gray substance of the medulla and 
pons. 

The diagram introduced (Fig. 52) will, it is hoped, make 
clear the main subdivisions of the spinal cord (which are sim- 
ply enumerated in its accompanying text, as a full descrip- 
tion of the various parts is reserved for the section which 
deals exclusively with the subject). 

We are now prejwired to study a section of tlie medulla 
(made at its point of junction with tlie cord), and to observe 
the changes in the gray matter which are produced (1) by 
modifications in the relative size of the columns depicted in 



250 



THE BRAIN, 



Fig- 52, and (2) by the decussation of the fibers which com- 
pose the *' crossed pyramidal columns" of the cord, shown in 
the diagram (Pig* 53)* 






\ 



XOqQA 



M 



N 



\ 



Fm» 62. — A tUa^ram to ihow the mtfre important mhdiviaioM of the tpifutl cord, 
(Altered from Flethsig,) 

D, anteilor homa; E, posterior bonis; (1, pray loltimdM of Clarke, which are not repn 
scnttid in the lumtfar or cervical re^on* of the eord. They are iniroduced herej 
however^ to enplaiD some subsequent points pertaimng to the architecture of the 
medulla ; y^. c, anterior white commissure ; n. g, c, antorior gray cotumiiSJiwre in front 
of the central canal; p.g,c.^ posterior gray cominisaurc : K, the eo-caljcd **cfo« 
pyramidal oolwrons" (see Fig. 46.); G, col um els of Tiirck, or the 8<M^lled "dip 
pyramidal columns^*; II, anterior root zoneii; C^ direct cerebellar oohimna ; M, col-' 
uninii of Itunlacb, or the ssMiiillc^l *' poatero-exlcmal eolufiins"; X^ columna of Goll^ 
or tli6 so-called '' poatero ioternal column " ; S, eensorj tract of lateral column, 
■OOOrdlDg lo Ggwem^ Ott, and others. 

In this section we perceive that the continuation of the 
COLUMN OP GoLL, or the so-called ^'/ascieulus gracilis,^^ of 
each side is increased in size by the addition of a ratiss of cells 
—the ^""clavate nuckus ^'~io its central portion (Fig. 53); and 
that the column of Burdach, or the so-called ^^/asciculus 
cujieatus^^^ also gains a collection of gray matter— the ^Hri- 
angular nucleus^^ — at a slightly higher level. 

The effect of this increase in size of the posterior cohinms 
is to crowd the gelatinous substance of the posterior horns to 



THE 8PIX0-MEDULLAR7 TRAKSITIOK 



251 



p.mr 




a.nhf 



Fio. 68. 



^ip either side, so that they appear near to the lateral borders of 
ir the section (Figs. 53, R, and 64, s g). 

Again, the crossing of the fibers of the '^ crossed pyramidal 
column" (Fig. 53) cuts off a portion of the anterior horns 
from the rest of the gray 
\ substance, and also tends to 
thrust backward the commis- 
sures, the central gray column, 
and the central canal. 

Other important modifica- 
tions occur, in addition to 
these changes of position in 
the component parts of the 
gray matter (depicted in Fig. 
63), as a result of the giving 
off of fibers (called *' arcuate 
fibers," because of the semi- 
circular course which they 
pursue) by the clavate and 
triangular nuclei of each side. 

These fibers pass to the oli- 
vary body of the same side 
(Fig. 54), and by their passage 
through the posterior horns of 
the spinal gray matter almost 

entirely separate the substantia gelatinosa and the posterior 
horn from the gray substance which surrounds the central 
canal of the cord. 

During the passage of these arcuate fibers, they become 
interlaced with the fibers of the crossed pyramidal columns. 
The latter decussate at this level, and serve to detach groups 
of cells from the anterior horn, which are thus carried into 
the anterior root zones (Fig. 63). 

Finally, the anterior root zones of Fig. 52 (now the lateral 
columns of the medulla) are subdivided by the arcuate fibers 
of the triangular and clavate nuclei, and the arcuate fibers 
of the inferior peduncles of the cerebellum into a reticulated 



_ _. A diagram of a Beetftm of the 
medulla at the middle of the motor 
decueeation. 

P, |)yramidal fibers undergoing decusra- 
tion ; a. c, anterior comu ; /. e.^ con- 
tinuation of the lateral column of the 
Hpinal cord ; R., continuation of the 
substantia gelatinosa of Rolando; 
p, c, continuation of the posterior 
comu ; T. n., triangular nucleus ; c, n., 
clavate nucleus ; p. m. /., posterior 
median fissure; a. m./., anterior me- 
dian fissure. 



252 



THE BiLilX, 



p.mX 



tie 



mXU 






r.r 



f firm at ion— the so-called '''formatio retieularis-^ — which is 
thickly studded with ganglitm cells jiossessing well-detined 
processes. 

The gray masses found in the reticular fiekl, considered in 
the aggregate, have been named by Spitzka tlie ''^ gaitylioii 

reihidarey It is the gangli<in 
proi>er of the medulla. It is well 
developed in the middle olivary 
plane, lying to the lateral side of 
the nucleus for the hypuglossid 
nerve. Spitzka regards it as the 
probable center ** for those rhyth- 
mical automatisms which (while 
under the control of the higher 
centers) involve the activity of 
both cranial and spinal nerves." 
The cells of this structure have 
more than one axis-cylinder pro- 
cess, according to the same au- 
thor, and exhibit apparent con- 
nections in all possible directions ; 
chiefly, however, in the dorso- 
ventral plane. 

Among the cells of the reticu- 
lar formation of the medulla two 
well-defined groups exist, which 
have been designated as the "^tti- 
terlor'' and ''posterior nuclei of 
the lateral column,^^ 

The nuclei of origin of the 
ninth, tenth, and eleventh cra- 
nial nerves are intimately asso- 
ciated with the gray matter present in the '' luetic ular field'' of 
the medulla (Fig, 59). Kmuse, Laura* Meynert, and Spitzka 
differ as to the probable connections of the so-called '' nn- 
cleus ambiguous" of Kmuse. Meynert associates it witli the 
tenth, Laura with the twelfth, and Spitzka with both the 



-ATa. 



(um,f 



Fia. B4. — A diat/mm of a section of 
the tneduUa at a MtigfUly higher 
level tftnn iu the prfccjinff fyure. 

P, pyramidal fibers ; N. «, Rrcifomi 
fibers; R^ rnphyp, with detrusfnit- 
ing fibei-si in the ticltl ; 0\ ac- 
cCiiSQvj olive ; (), olive i /. r.f 
fgrmalio retieiilftriy ; t*. c, cen- 
tral canal ; n,f,, lateral nueieus; 
f.^., substantia ^clatino^a: n.r.^ 
nucleus cinicatki^ ; /* c, ftjnicu- 
lua cimeatus ; f^g., funicaluB ^n- 
dlia; w.vy.^ nueliii^ of tlie saiue; 
n. XI, nucleua of the eleventh 
ncrre {i*piual accessory); ii. XJI, 
tame of t\w livpofrlossai nerve ; 
a,m./., anterior median Itfisure; 
p, m,/*t pofltcrior median fissure. 



NERVE NUCLEI IN THE MEDULLA. 258 

^tenth and eleventh cranial nerves. The fibers arising from 
it cross the raphse of the medulla. Spitzka believes that it 
Is probably connected with the motor apparatus of the 
larynx. 

The ^^ ganglion ceZZ^'' which are found within the gray 
matter of the spinal cord are more or less redistributed within 
the medulla, after they have been separated (at its lower por- 
tion) by the fibers of the crossed pyramidal columns and the 
atenate fibers already described. Nuclei of special nerve 
roots, and masses whose functions are not yet well under- 
stood, are thus formed. These will merit subsequent descrip- 
tion. 

The nuclei of the lateral column of the medulla^ which 
have been previously mentioned, appear to give origin to a 
I>ortion of the fibers, at least, of the spinal accessory nerve. 
Some of these fibers may be distinctly traced to the nerve of 
.the opposite side, but the majority wind around the postero- 
lateral group of cells to join the nerve of the same side. 

As we ascend the medulla, cross-sections of that body at 
different levels successively reveal the nuclei of the motor 
fibers of the pneumogastric and glosso-pharyngeal nerves; 
next, those of the facial nerve ; and, later, those of the motor 
or ascending root of the trigeminus. 

Nerve Nuclei in the Medulla. — By referring to the dia- 
gram which is now introduced (Fig. 66), and comparing it 
with the one which follows, the reader will be enabled to 
form a tolerably clear conception of the relative situation 
and extent of the more important nuclei, from which some 
of the cranial nerve-roots apparently take their origin. It 
can be more readily understood, after a careful study of 
these two diagrams, why it is that cross-sections of the me- 
dulla and pons made at different levels present such wide 
variations in the arrangement of the gray matter. These di- 
agrams will help also to render such sections more intelligible 
to the reader. 

Let ns now consider somewhat more in detail the jmints 

which these two diagrams present. In the first place, it will 
19 



254 



THE BRAI^., 



be seen that the cranial nerves from the fifth to the 
escape from the pons or medalla at different levelsw 

Agaitt) it wiJl be observed that the nuclei of origiii^ 
nerves are situated in the region of the^/toor qftht/oi 



R.5. 



0.- 



5- — 



\^ 



— 9. 



IV-Ki^-Wa 



^^. 



mo9i important fitiffri ; ri^fU half of tht medut/ft^ **fit frmn fhe furf^nce of mA 
parU that lU doaer to ihU aur/ace are deeper thtnini, (After £r!>. ) 

Py^ pyramidal tract; Pj. Er., decuji^Ation of pyrarui^ltt; O, oHv»ry bod^ ; 0,a 

olivnn- body; 5, motor; f>\ midiil*; Bcmsory; h'\ inferior seosoiy iraclm vfi^ 
gC'imnQB; d, nuctciis of iib<iucetis; G. /, f*cnti fidilU ; 7, tkorlciM tmekSki 4 
poBtcrior mcdinu acotmtic Dueleiis ; 0, glo-iso-phiiryiigt^Ml tiuctvu^; tO, uodcv v 
vugUB; llf fipinal ncceji^^ory nucleus; 12, hypoglossal micl^un ; Kz., ft«idi«f ^ tt» 
fimiculus graeilia; K, 5, trig^emiaUB roots; ihos^ of the U. G, abdvicinai^ ««i K.1^ 
lifedaliti, "^^ 



entnclej and that they are so distribnted (with few ej 
tions) as to approximately correspond to the level nf tl 
saperficial origin of the nerves whose roots are euni 
with them. 

In the third place, it will be seen that some nerves hivir 
more tliaa one uueUmH of origin in the medulla. The fi/tk 
has one motor and two sensory nuclei, near the npyw^r r^ 



NERVE NUCLEI OF THE MEDULLA. 



255 



^^6 ventricle ; the auditory has four nuclei, the anterior and 
f»posterior median, and the anterior and posterior lateral ; 
cfinally, accessory nuclei have been discovered for the facial, 

spinal accessory, and hypoglossal nerves. These are not 

shown in the diagrams. 



Thftl.^-1 




Fio. 66. — Dia^fram of the chief tracts in the medulfa. (After Erb.) The formatio 
reticularis is represented by shading. 

OL, oIlTary body ; V, anterior ; S, lateral, and II, posterior spinal funiculi ; a, pyramido- 
uiterior tract; d, pyroniido- lateral tract; Py., pyramidal tract; h, remainder of ante- 
rior oolaron ; e, rmnainder of lateral column ; «, e^ cercbcUo-lateral tract ; /, funiculis 
gntdlic, and f, nucleus of the same ; ^, funiculus cuneatus, and ff\ nucleus of the 
■tne; V.e. i, Internal fasciculus of the pedunc. cerebcUi ; 1*. e. e.^ external fasciculus 
of the same ; Cq. F., tract from corp. quadr. to format retic ; Cq. 0., the same to 
the oliTwy body ; Thai., tract from the thalamus opticus. 

In the fourth place, it should be noted that the area cov- 
ered by the nuclei of some nerves is greatly in excess of that 
of others. The trigeminus ner\'e has one sensory nucleus 
(the inferior) which extends throughout the greater part of 
the Bubstance gf the pons and the medulla (Fig. 56, V); 



256 




THE BMAIN, 



while the •* median sensory" and the ^"^ motor "^ mtclei 
same nerre are of smaller size. The ninth, tenths ek 
and twelfth cranial nerves have longer nuclei than ili-- 
enth or eighth. 

Having now grasped the general situation and formodbl 
nnclei of the cranitd nerves found within the pons attl i 
duUa, it seems advisable to add a few statements 
the peculiarities of each, which may aid us in stTM^v-fiLrt 
architecture of the medulla and pons by cross-sec r: 
same. 

The tfigeminal sensory niu'M are analogous in -^aei 
spects to the posterior horn of the spinal gray mauar, ! 
they contain only small ganglion cells. 

The nucleus qf the sixth n<rr»e contains large cells *i> 
tor), and lies at the junction of the pons and medulla, bs I 
groove on the floor of the fourth ventricle, near the fasdcihi 
teretes* 

The nucleus of the facial nerve Is composed ot liqp I 
cells (motor), and is somewhat lower and placed 
deeply in the substance of the medulla than that at dil 
sixth. 

The auditory nerve receives fibers from four indepe^Ut 
;wrf^?i which are situated in the region of the broadest {Mf- 
tion of the fourth ventricle. 

The pneiunogastric and the glosso-pharpngeal nenB 
have nuclei of origin which are not clearly demarkated fro* 
each other, although the nucleus of the vagus lias deeper 
than that of the ninth nerve. 

The following table is given by Spitzka to illustrale tkt 
various nuclei of the medulla that appear in cross sedio» 
made at different altitudes and at a right angle to the hu 
axis of the medulla. 



1 Spilzka eomhaU the view that a diffcn^ntiatlon of cerv^ o^tU in fr^;»n! 1o 4^ 
fimcdon can be nmde on their dimensioQi! alooo. He points out tluil botli liff»tff 
tDaltipolar cells mar bare & Bicii«ory function, And thit tooM inolor ^Is Imiv CWv ^»> 
oemcj} in the lover rertebnitcs. He tdatca that t gradual tnusltioii from lit* \mAf tpikr 
[iri>oe4isc9 U typicii of tnotor ftttributes^ tod that, in tcnaofy cetUt, Hh 
Always abrupt. 



Boots nfetb 

Exit of 5th 
pmir. 




Xodens of 
4th pair 

Kadeiu of 
Sd|Mir 




The areas represented by Pn and G in Fig, 69 are believed 
by Spitzka to be respectively associated with the fibers of 
origin of the pneumogastric and glosso- pharyngeal nerves. 
He considers them, therefore, as nuclei for '* visceral innerva- 
rions-' and '* gustatory impressions.'' He is led to this con- 
clusion from the variations observed in animals as regards 
the deveh»pment of these nuclei, and ihe prepondenmce of 
these cell-masses in the planes of the raediilhi marked by the 
exit of the rootlets of the pneumogastric and glosso-pharyn- 
geal nerves* 

Some authorities give to the pneiimogastrte nerve a sec- 
ond nueleus of origin in the substance of the medullar near 
the olivary body. 

The hypoglossal nncleu^ ' lies close to and in front of the 
centiul canal of the cord, as low as the level of the decussa- 
tion of the pyramidal til>ers. It consists of large branching 
nerve cells, simOar to those of the anterior horns of the spinal 
cord. After the central canal has opened into the fourth 

^ The Bttcltnis of the hrp<>^lo^^<^1 nerve is coiiJ>iflercd hy Spitzka as a oontinnntion up- 
ward (a?phatad) of the gcUtinous graj matter lying in front of the spinal canal. The 
•nierioT htirn« have been cut off (in a lower plane of the rai^dulla) by the decussation of 
the pjramidal fibers. 



:i 



258 



THE BRAJN. 



ventricle, this nucleus creates a prominenoe close to the 
dian line of the ventiicle, Hliglitly aI)ove the point of the 
mus scripturius, or the lower angle of the ventricle. 



ep 



VI 



B yiii 



£ 



Fso. 67> — A er<a»-4^hn of the medulhi *yn a kvel wUA tk$ 9mm 

of the audithrii tierve. (M<Miitied frt/ro Flochiig b^ Roml) 

ip and ep, the iotetTinl nnil external dirisionf? of tho inferior jtr^^-^-* f the ( 
yVj*, !\Hicular formation; a^ ardfomi fibers; R. Vlll, root • x^Yfr; 

Vlll ', miclei of same; H, hypoglopBal nucleus; P, pyran 1 , ^ , Lii.ia^m 
of same; po, parolivary bodj; np^ nucleus of the pyramid ; at^ ascvndii^ J 
iicrrc; aKr, direct cerebellar tnM;t; L» posterior longitudtiiJil bondle ; 0»<* 
iff, substaxttin gelatmosa. 

That the fibers of the hypoglossal nerve are proloi 
some way upward to the cerebral cortex seems to be 
by pathological facts; although they have not yet been 
to such a tennination. 

The medullary portion of the spinal acceesory m 
destined to join the pnenmogastric nerve after ite exit 
the skull, while the spinal portion pursues a separate 



tfii^^ 



MOTOR NUCLEI OF MEDULLA. 259 

JLts nucleus seems to be a prolongation downward of the nu- 
-49]eas of the vagus, as its course would naturally suggest. 

In a general way, it may be stated that the nuclei of 
those cranial nerves within the medulla which are motor in 
Sanction are characterized by large multipolar cells, while 
'those which are connected with the sensory nerve-roots are 
composed of cells of smaller size, some of which are bipolar. 
In some respects they are analogous respectively to the cells 
of the motor or kinesodic, and the sensory or aesthesodic re- 
gions of the spinal gray matter; and also to the gray sub- 
stance of those convolutions of the cerebrum which preside 
orer similar functions. 

Spitzka has called attention to the fact that the evolution 
of nervous force does not necessarily imply the existence of 
distinct fibers and of nerve cells. He says: '^In the lower 
forms of animal life a uniform blastema, with or without 
nuclei, and entirely devoid of nerve cells, is frequently all 
that represents a ganglion ; and the afferent and efferent 
strands connected with such a simple structure are composed 
of an infinite number of granules which show no fibrillary 
arrangement." 

Again, the same author remarks: "The increased perfec- 
tion of the nervous system is marked by a progressive tend- 
ency to isolation of the conducting strands." 

The Upward Continuation of the Anterior Horns 
OP THE Spinal Gray Substance.— We have already men- 
tioned a change in the anterior horns * at the lower part of the 
medulla produced by the decussation of the motor fibers, 
which compose the so-called ** crossed pyramidal tracts.'' 
The formation of two groups of cells, called the anterolateral 
and the i)ostero-lateral groups, here takes place. Portions 
of these groups are carried into the lateral column of the 
medalla, and form the so-called ''anterior^' and ^''posterior 

I Tbe nMdeuB of the pyramid is to be regarded as ** the amputated part of the ante- 
rior bom ** of the corresponding side of the cord. Spitzka ro^^ards it as an accessory 
•adeiii to the hypogloaaal nerre, classing it in the same category with scattered gray 
mmn from tbo latoral system higher in the medulla. He believes it to be the nucleus 
of origin of thoM fibers which supply the retractors of the hyoidean apparatus. 



The bsaix. 



nucleP^ of that colnran. The same arranjcr<»nient appoBt 
be carried out as we study ascending seetiau.% so tliat 
spinal accessory, the motor fibers of the pneumoga&tTir 
glosso-pharyngealj the facial, and the motor tiliere of tkf 
gerainus seem to spring from a eontinnatioD apward ol 
anterior horns of the spinal gray substance in lis 
column. 

The fibers of these nerves take, as a rule, an exi 
circuitous coursfe before escaping from the medulla, b 
case of the facial nerve, a peculiar bend in its fibem of 
has been named the '*knee" C^^ffenu nerci /t^rlali^^). 

The anterior nudeus of the latenU column of the medaDi 
appears to cease on a level with the origin of the facia) wen^ 
although some authors believe that some fibers of the txig^ 
inns pass from it in an upward and backward direetkoL 



tllfe 



Tr. 



:^i7 



Tr 

Fig 6d. — A tramtmrm mtimm ^krrn^k ,■ : . ifith ikt rooc* <*f tkg^ 

MtffHih mMitf/ ikcnwi yVam d nime moi^tki' mi6i<^o. (Modified from Erb i 



Tit n^ h»\i r^Tc* 
WbtKB ol Hm |MNi- 






: K, routif 1 f t^ |^A>^ 

r mot lom ' inu<«rf; 

i'lr nQcl<*tif of ^^mc. Tkik fi^fi 

uU fibers wiMh the hotimmttX {U 



TEE H7P00L08SAL NUCLEUS. 261 

The posterior ntbcleus of the lateral column of the me- 
dulla passes behind and to the outside of the nucleus of the 
abducens, or sixth nerve, before joining with that of the facial. 

The development of the olivary body within the substance 
of the medulla tends to displace the whole of the gray matter 
backward, until the posterior gray commissure (Fig. 52) dis- 
appears, and the central canal of the cord opens on the floor 
of the fourth ventricle. 

The nucleus for the hypoglossal nerve roots bears a strik- 
ing analogy, as regards the peculiar distribution of its cells, 
to the anterior horns of the spinal gray matter. The analogy 
is heightened furthermore by an identical method of develop- 
ment of these groups.' 

At the upper level of the hypoglossal nucleus the trans- 
Terse fibers of the pons tend to separate those masses of gray 
matter, which are probably an extension upward of the an- 
terior horns of the spinal gray substance, or the gelatinous 
substance anterior to the central canal. Hence it becomes 
extremely difficult to trace their connections. 

In the larger nucleus of the hypoglossal nerve, Spitzka 
describes a collection of cells whose axis-cylinder processes 
run away from the tract of the hypoglossal fibers, rather than 
toward them. These cells he believes to be associated with 
the eleventh nerve roots ; and he thinks that an associating 
mechanism is thus established between the movements of the 
tongue and of the vocal cords, as is required in phonation 
and singing. 

There are some grounds for the belief that the nucleus for 
the abducens, or sixth nerve, is a direct continuation of the 
postero-lateral group of cells ; because the fibers of the facial 
nerve wind around it as those of the spinal accessory nerve 
do around the postero-lateral group in the lower part of the 
medulla. 

'Spitzka makes use of the following general deduction or axiom: **A ganglion 
(oeBter) follows in development the development of the periphery, which in projected in 
that ganglion.*' Ue advances many interesting facta in support of thiB law, from a study 
of the comparative anatomj of animals. *' Journal of Nervous and Mental Diseases,'* 
Oetober, 1879, p. 616. 



202 



THE BBAiy. 



The tmeleus for the moior-oeuli^ or Unrd njtrtt^ *UA| 
has been partly described in the page» that treat dLm\ 
cru9 cerebri, probalily belongs to a gronp of cellK wbiefc \ 
const! tntes the nucleus of the abducens nerve* In point << I 
fact, it is reasonable to consider the nndei of the iMri 
fourth, and sixth cranial nerves as parte of one mam4\ 



^ 



m 



V 



\% 



^ 



^ F**& 






<%\5 



i£ir\ 



—-- . .>' 



J. 



FlO. &9« — A frofuriferstf seetion of the meduila i partly nehemaHt) nuuU thr^m§k j 
dU q/ ffie otivnry hodjf, (Modified frotu Splukn.) 

H, ftnd A, nuclei of origin of the h/pogtossal ncnre (twelfth cranial) ; F ft , rrtW 
formation, with its cjell-masse? ; 0» olivary body; P, iryrftmid ; a. ^tm 

dian fiasura; 6 and Pn, mae&e^ of colls probably aasociated re»f) cfc ^ 

gloflso-pharyngeal and pncumog^astric nerves; Va, n^.'^nJirnT r....^ ,,^ ^^^^ ^lami 
norre ; D, resttform column ; a,/., arcuate fiber; ; F. iinnigli ibt |pl» 

olivary trnct; € and d, bundles of fibers from the p*^ traeCu^ c«l H^^ 

on their way to the inferior eercbellmr peduucle nft^r Ueeu^iiaiion ; T, tbe ** Uliwm rf 
fasciculus " of Spitzkii; '* solitary '^ or ** round ** btmdie of other amhuroL K«to ito 
the solid nna53tc.«^ are eomnoded r»f cells ; the black areas are de^^igni^fl to mn^Bl 
conducting fibers running vertical to the plane of the section; the «rhit« UtiM 
ftcnt fibers which run in the plane of the section. 






cells, which have become separated by the interpo^t 
of some fibers destined to play an important but UDknoi 
part in the varied functions of the medulla, The»e ni^ 
del all act upon the eye. They are connected, accordi]i|| 

distinct fibers, which run from the 
that of the third nerve of the 



to some authors, 
abducens nucleus 
site side. 




GELATINOUS SUBSTANCE OF MEDULLA. 363 

The Upward Continuation of the Posterior Horns. 
— ^The arcuate fibers of the medulla separate the '^ substantia 
gelatinosa " from the rest of the gray substance, near to the 
line of junction of the spinal cord. This portion of the pos- 
terior horns maintains a superficial position in the lateral col- 
umn of the medulla, as high as the point of escape of the tri- 
geminus, or fifth nerve from the pons. In the opinion of 
some authors, this structure may be regarded as prolonged 
through the aqueduct of Sylvius as far as the level of its 
opening into the cavity of the third ventricle. 

Spitzka is led to the conclusion that the gelatinous svh- 
stance of the posterior horn is not composed of neuroglia 
tissue, but is to be regarded rather as imperfectly organized 
ganglionic tissue which is connected with sensation. He is 
brought to this view by the following facts: 1. It exists 
where the sensory nerves enter the posterior horn ; 2. It is 
found in the sensory nuclei of the medulla, chiefly in the 
trigeminal nuclei ; 3. It is found in the olivary bodies which 
are connected with strands from the posterior columns of the 
cord, above the nuclei of those columns. 

The i)osterior spinal comua are continued upward into the 
substance of the medulla upon the mesial aspect of the 
ascending root of the fifth cranial nerve (Pig. 57) as two mass- 
es — the so-called "spongy" and "gelatinous" form of gray 
substance. The former merges with the gray matter of the 
reticular field ; while the latter lies more closely related to the 
trigeminus tract. Spitzka is led to believe, from the apparent 
connections of the gelatinous substance, that it is the station 
for sensory impressions derived from the pharynx. He states 
his grounds for this belief as follows : 

"Taking into account that the three nerves, into which 
the eighth jmir of Willis has been divided by Soemmering, 
supply many peripheries conjointly, I think it unfortunate 
that investigation should seek for the special nucleus of this 
or that nerve, designated by a given numeral. Meynert made 
a step in the right direction when he considered the nuclei of 
the ninth, tenth, and eleventh pairs in the aggregate, and 



264 



THE Bi 



classified the aggi'egate nuclear masses on the topjgniiJiifii 
principle. If there is any truth in the notion that, will i 
given animal species, cells have special connections, p; 
special type of structure, then it will b<? reasonable lo 
for the nuclei of different peripherieif*. This procedure is 
more rational than to seek for the nucleus of a nenre 
component fihiments have different peripheral ternrir ^ 
and are included in the same sheath, rather by ul. 
accident, as it were, than because of theix' phyHiological 
pinquity. I think it sound to speak of a nuclear col 
representing the visceral periphery of the va^is, or th« 
tory periivhery of the glosso pharyngeal and inte 
nerve of Wrisberg, or the tactile periphery of the ninUi 
tenth, the motor pharyngeal periphery of the same Qem% 
and the motor laryngeal of the tenth and eleventh pairn.** 

The Continuatiox of the Central Gray CoLimt 
THE Spinal Cord.— By a reference to Fig, 62 it will lie «a 
that the gray substance of the spinal cord on either side ot 
the central canal is represented as consisting- in j^rt of ik 
'*gray" or ^'vesicular column of Clarke ^^' and a<£nitn of an 
intervening portion between it and the central canal 
the ^^ central gray column^ * 

The coLTTMN OF Clarke is well defined In the dorsal 
of the cord, but it is not represented in the cervical or lanil 

* Tlie ^ny matter or the core] is dirided hy Spitzkii Into three p«rts^ Hx. : tJs* if**- 
nor hoiiid, or motor system ; the posterior horns, or t^cn^ry syf t<*iii ; mxu\ tbe ItticnvA 
ate portioti, to ^hicb he Applies the term ** mixed sjstom/* t>ec4itifte it jNiTtalcei| ttt to 
mindj of aenfiury, motor, and trophic fuuctiona. He attributes a trophic fuiKctJOA C» ite 
cells of Ctaike';< column. 

The folio win;: formtilfle, advanced bj the same author respecting the fuaetioBi rf 
cell groTips in the central tubular gray masse.^^ arc of intere-it in this coti&fHMton : 

^' The nearer the mu^cte i« to the ?entral at^pe^'t of an anima), the nt<arer iriU Iv km 
nucleus to the medjan line of the cord. Per cnnira^ the nearer the mii^'te is tu tlie daml 
line of an m^ima], the nearer to the t^a-eall«l lateral comu vrill H9 nucletis Kftte tA Ktf 
nought for. Flexor niidei are therefore in internal, cxtenfor niietei in imtcrtiftl ^t^ m^ 
terior, eell gmups.'* 

'* Uypertrttphied tegmenta of the body^ fucb an the cxtrernlti^ are iMsconupmd^^ bf 
lateml ottenstont* of the corntia, in which flexor and extensor muscles probatilj 1 
the same relative po«ition m the one stated, 

^* Whether ^rrnipg of muBcles be flexor or extoDi^or, it will be found tl»*t the i 
thej afe to the animal axi», the nearer will their nuclei be to the central oitiat TlikM 
eipecialljr true of the flexor iiuoleL** 





ACCESSORY NUCLEI OF MEDULLA. 265 

i^ons. In the lower part of the medulla, however, a collec- 
tion of cells sitaated at the posterior and external part of the 
central gray column may be discovered, which bear a close 
analogy to those of the column of Clarke encountered in the 
dorsal region of the cord. It contains hipolar cells which are 
markedly pigmented, and constitutes the posterior nucleus of 
the spinal accessory nerve, which is given oflf at this level. 
At higher levels, after the central canal has opened upon the 
floor of the fourth ventricle, this column seems to assist in the 
formation successively of the nuclei of the eleventh, tenth, 
and ninth cranial nerves. 

The CENTRAL GRAY COLUMN of the cord appears to be con- 
tinued into the medulla as a thin layer of gray substance 
which covers the floor of the fourth ventricle, and is prolonged 
a8 a lining to the aqueduct of Sylvius. 

The term "nuclear formation" is applied to the cen- 
tral tubular gray, because it exhibits a tendency in higher 
animals to resolve itself into nuclei of origin for special 
nerves. 

The fourth ventricle may be regarded as an expanded por- 
tion of the central canal of the cord, in order that sufficient 
room shall exist for the nuclei of the cranial nerves situated 
upon its floor. 

The aqueduct of Sylvius^ with its surrounding gray 
matter, again represents from this standpoint the spinal 
canal and the central gray column, continued onward to 
the third ventricle. 

ACCESSORY NUCLEI OF THE MEDULLA OBLOXGATA. 

Within the apparent continuation of the central gray col- 
umn of the cord upon the floor of the fourth ventricle and the 
aqueduct of Sylvius, certain collections of cells, that have no 
representation in the architecture of the cord, are observed. 
These have been named the ''^ accessory nuclei '^^ of the medul- 
la. They require a separate description. These include the 
inferior facial; the accessory nuclei of the spinal accessory 
and hypoglossal nerves ; and four acoustic nuclei. 



TffS BliAJ: 



lijferior Facial JVudetis.—This was first descriM^ 
Clarke. It consists of a rollection of several " rna^MSt 

cells, whii'h lie to the inner side of the hyp ^,. J o 
and close to the median line* Before the 8pmal canal 
into the ventricle, they lie between it and the hypcgl 
nucleus of either side. The libers which spring from ll 
appear to enter the funiculus tei'etes, thi'ough which 
ascend to the fasciculus tei^etes, and then join %Wth fibm 
the facial nerve. This nucleus has been divided by soqm 
thors into two, to which the names internal and external 
been applied. 

Aeeessory Nuclei of the M^pinal Accessory iVenJr,— 
consist of two coUectians of cells of small size, which are 
ated posteriorly to the main nucleus of the spinal a 
nerve. According to Meynert, these nuclei ar^ connected 
commissural fibei-s which pass posterior to the centnil canal 

Accessory Nucleus qf the Hypoglossal Ner^e, — Rim d^ 
scribes this collecti(jn of cells as developed principally npfli 
one side only of the medulla. It is composed, according ^ 
this author, of caudate cells of extremely small size, wfcei 
compared with the cells of the hypoglossal nucleus. Ha l»^ 
lieves that this accessory nucleus is concerned in the meclmi' 
ism of articulation, and that it is reasonable to snpjiose thitit 
is in some way connected with the third eonv<dutiun 
left frontal lobe. 

Special Nuclei of the SIedulla and Pons Varoux 
Ross includes under this head the acoustic nnclci, beca 
they can hardly be said to be represented by any jjart o: 
gray substance of the cord. They are four in nnmber, rro 
median and two lateral. 

The posterior median acuusHc nucleus occupies the 
between the ala cinerea and the inferior peduncle of the 
bellum« as high as the anterior border of the *' strife mediillft^ 
res." It gives origin to the posterior root of the auditai 
nerve. Some of these fibers pass out superficially, the ^siri; 
acoustics"; while others traverse the substance of the IM^ 
duUa. 




r, m^ 

It. 

4 





GANGLIA OF PONS AND MEDULLA. 267 

The anterior median acoustic nucleus lies anteriorly to 
the strisD medullares, and gives origin to the anterior root 
fibers of the auditory nerve. It occupies the external angle 
of the ventricle. 

The posterior laieral acoustic nucleus lies imbedded in 
the i)eduncle of the cerebellum, and is interposed between the 
8Ui)erficial and deep fibers of the auditory nerve. 

The anierior lateral acoustic nucleus is situated between 
the middle peduncle and the flocculus. It gives origin to the 
so-called "portio intermedia of Wrisberg." The view that 
this nucleus is associated with the special sense of taste in 
the anterior two thirds of the tongue (because its fibers appear 
to i)ass in the chorda-tympani branch of the facial nerve) is 
now held by some anatomists. 

The Superadded Gray Matter of the Medulla and 
Pons. — When successive cross-sections of the medulla and 
pons are compared with each other, nodal masses of gray 
matter are discovered, the analogues of which are not found 
within the brain or spinal cord ; and some are apparently not 
directly connected with the fibers of origin of special cranial 
nerves. Most of these have been incidentally referred to in 
previous pages, but a few remain to be described. These 
nodal masses include (1) the so-called " triangular nucleus ^^ ; 
(2), the ^^clavate nucleus ^^ ; (3), the ^'olivary hody^^ ; (4), the 
^^parolvbaryhody'^ \ (5), the *'' internal parolivary hody^^^ or 
the ^^ nucleus of the pyramid ^^ -, (6), the ^'superior olivary 
body^^ ; and (7) the ^'middle sensory nucleus of the trigemi- 
nus nerve.^^ 

The "red nucleus of the tegmentum^' or the ^^ superior 
olite^ of Luys (which has been already described in connec- 
tion with the crus cerebri), as well as the '''external geniculate 
body" (which has been discussed in previous pages), are also 
classed by Ross among these superadded collections of gray 
matter. 

TTie Triangular Nucleus. — This is a gray nucleus (Pig. 
58) which is inclosed within the substance of the cuneate bun- 

' The fMrdlTuj bodies are often designated as the *' accessory olivary nuclei/* 



208 



THE BEAIA. 



die or Burdarh's eolnmn (Tig. 52). It extentla cepbilfl4ln| 
the lower portion of tlie medulla a8 high as the poMeritff i 
of the *^postero-lateniI acoustic nucleus,'' and inrivaiie^il 
8126 as it ascends. It lies along the iniier border of thtcm 
form column. It is now believed that all the fibers of i 
postero-lateml column of the spinal cord (Burdach^s coli 
end in this nucleus. 

77ie Clamte Nucleus. — ^This ma^ss (Pig. 63) is sin 
within the continuation of the fasciculus gracilis ortliei 
umn of Goll (Fig. 52) into, the medulla. It x^i*oduce^»ai 
largement of this bundle of libers called the **c^</m," 
extends as high as the posterior extremity of the 
lateml acoustic nucleus." Both the clavate and 
nuclei may be considered, therefore, as pillars of gra^i 
tance which run in the long axis of the medulla. The I 
rhich compose the posteromedian column of the spinal \ 
(Goirs column) probably end in this nucleus. 

The nuclei of the columns of Goll and Burdach gradii 
disappear as the central canal of the cord expands imo 
fourth ventricle. 

The Olimry Bodt/.— This structure (Pigs, 67 and S8) h^ 
situated in the lateral column of the medulla, close to tbei 
tenor pyramid. Its ffraj/ nndens in not seen npon itjs 
face, since it is covered by longitudinal and transven^e fibfis 
The olivary body takes the form of a scalloped or wanr lajw 
which is open at one point — the kllus of the olire. Tte 
opening looks toward the median line of the body, Tbe 
libers which pass thiough the hilus compose tbe so-caUfli 
** peduncle qf the oUm.''^ Some of the relations whieb tkii 
body bears to other parts are d<*picted in a previous diagtia 
(F'ig. 55). Certain libers of the olivary peduncle pass thnrnftk 
the lamina of the olivary nucleus, and constitute the so-called 
'*ai'cuate fibers" (which have been mentioned on a prerioiis 
page as helping to subdivide the gray substance of the anl^ 
nor horns at the junction of the medulla and spinal ooid). 
The cells of the olivary nucleus {carpus denMnm of t) 
olive) are of the multipolar variety and of small size. 



FIBER TRACTS OF THE MEDULLA. 

The olivary bodies are functionally related to the cerebel- 
lum. It has been shown that atrophy of one hemisphere of 
the cerebellum is always associated with atrophy of the oppo- 
site olivary body. The fibers from the olivary bodies pass to 
the cerebellum by means of the inferior peduncles (processes 
e cerebello ad meduUam— restiform bodies). 

Spitzka has pointed out the fact that the gray nucleus of 
the olive, as well as the clavate and triangular nuclei of the 
medulla, are highest developed in man and the anthropoid 
apes. 

The Par olivary Bodies, — These are shown in Fig. 57. 
They are to be regarded as accessory nuclei to the olivary 
body. One, the ^' internal parolivary hody^^^ lies adjacent 
to the internal half of the posterior border of that body ; the 
other, or '''' external par olivary hody^^^ lies in front of the 
olivary body, and to its inner side. Because the latter lies 
immediately behind the pyramid, it is often called the ""'nu- 
deus of the pyramid.^^ The fibers of origin of the hypo- 
glossal nerve pass between the olivary body and its internal 
accessory nucleus after traversing the peduncle of the olive. 
Occasionally these fibers penetrate the olivary body. 

The Superior Olivary Body. — This long gray column lies 
in the pons Varolii, in front of the facial nucleus. 

THE WHITE SUBSTANCE OF THE MEDULLA. 

Having now considered the collections of nerve cells or 
gray matter within this ganglion, we are prepared to intelli- 
gently discuss the bundles of nerve fibers which constitute its 
white substance. 

In order to systematize this study, it is necessary to im- 
press you early with the fact that two general classes of fibers 
may be recognized here, as follows : (1) Those which are pro- 
longations of the fibers /bz^nd within the white substance of 
the spinal cord^ and (2) superadded fibers^ which are inde- 
pendent of the spinal bundles. 

The fibers which are prolonged from the spinal cord prob- 
ably traverse the entire length of the medulla and pons, either 

20 



270 ^^^ BRAiy. 

totally or in part, and then pass to the cerebmm throu^ ^ 
peduncles (the crura). These bundles are found, as a rein • 
occupy jpar^/o/i5 of the internal capsule (F%. t^* -'* -^ ' 
ing the eras, and to be connected with the cell 
bral cortex, after they have escaped from the confines d 
basal ganglia, and have radiated throughout rations irai 
the central mass of the cerebral hemisphores. 

In previous lectures we have traced some of the b» 
dies of the internal capsule from above downward, ulai 
their cortical attachments as the starting-point in oardoc# 
tion. It is now deemed advisable to reversie the order oii^ 
scription, and to tmce them from the «pinal cord 
noting certain peculiarities in the course which each 
during its passage successively through the medulla^ 
cms cerebri, internal capsule, and corona rudiata, an nidi 
the area of the cerebral corteit, to which each is probahlv 
tributed. Some difficult points wll be made cli^ar to 
reader, while following the description of these fiben 
reversed order, by consulting certain familiar diagrama wl 
have been used in elucidating previous topics (chiefly 
8 and 63). 

The diagmm of the main subdivisions of the spbial coii 
to which reference was made on page 250, will also coice \i0 
play again here, as the 8tarting-i>oint from which the diifera^ 
bundles of the medulla are described^ 

The Pyramidal TnAcrrs.— The motor bundles, which !wr^ 
to connect the cells of the cerebral cortex \^ith the ceUa of d^ 
anterior horns of the spinal gray matter (Fig, 52), are fraaA 
in two distinct columns of each lateral half of fli»» sT^iai! 
cord. 

The columns of Turek (Fig. 46) convey those bundte; d 
spinal fibers which are associated with the cerebral heid- 
sphere of the same faide. These do not decussate* In ri,.. ttv^ 
dulla. 

The " cromed pi/rarnidul eolnmns^" (Fig. 46) convey 
which cross within the medulla to the oppc^site -^ 
which are therefore connected with the opposiui c^ivi^** 



liUi. 




THE BUAIN. 



the motor convoliitiona of the cerebrom, which chiefly \^^ 
the fissure of Rolando. 

Within the substance of the spinal cord ihls tra* . 
gradually diminishes in size fi*om above downward. Tto 
because small fasciculi are jL»iven off constantly (in the 
segments of the cord) to the anterior granglion-cells 
spinal gray substance. The coluinns of Torek nsuallr 
fiear at about the middle of the dorsal region. The 
pyramidal tract" of the lateral column extends to Um 
limits of the cord (origin of third or fourth sacral 
gmdually diminishing in size, however, as it descendit 

The hypothesis that libei*s also leave the pyramii 
at various levels in the pons and medulla^ and pass bad 
close to the raphe to join the cranial nerve nnclei^ 
be confirmed by late investigations. Some of these fibifS 
questionably decussate within the rai>he. 

Flechsig has shown that the relative proportion of 
and direct pyramidal libers varies greatly in Individ oiik h 
a few of the spinal cords examined, he fonnd that d? ih 
^Jibers decussated ; while, as the opposite extreme, cas^iw 
fclso observed where no decussation occurred^ all the filw 
passing directly downward in the region of Tunrk's colmii^ 
These observations help to interpret those rare eases in wtoA 
hemiplegia has occurred upon the same side as the c«!i«boi 
lesion wliich caused it. 

The diagram which I now introduce (Pig, 60) will lllQstiil« 
the areas occupied by these fibers throughout the spinal cfiri. 
and the filaments which the two columns of each lateral half 
of the cord give o% during their descent, to tlie cells 
anterior horns of the successive spinal segments. 

The Accessory Fibers of the Pyramidal Tuact, 
cross-sections of the medulla, made at ditTerent levels* bo; 
of fibers, which are to be regarded as accessory to the 
pyramidal tracts already described, are seen to occnpy 
anterior and internal margin of each pyramid, and aL*o ihit 
part of the lateral column which adjoins the gray substaimf 
particularly the so-called ** formatio reticularis. ** 





ACCESSORY FIBERS OF MOTOR TRACTS. 



273 



s: In the upper portions of the medulla these accessory fibers 
become very abundant and tend to aggregate toward the 
ji? pyramids. 

y Within the substance of the pons some of these accessory 

: fibers lie to the inner side of the longitudinal bundles ; in the 

:r crura they appear to pass along the inner side of the medul- 




pynmlfd-Rl 
tract. 



Fio. 60. — The path* of the nuAor Jibern of (he cord. (Modillcd by the author from 

BratuwcU.) 

The lines show the course of the fibers given off from the pyramidal tracts associated 
with the left cerebral hemisphere to the cells of each spinal segment and their 
continuation into the motor roots of the spinal nerves; the arrows indicate the 
direction of the currents ; C. P. T., crossed pyramidal tract ; S. G., substantia 
gelatinosa. 

lated fibers of the '* crusta" of either side ; finally, they main- 
ly reach the cortex of the frontal lobes of the cerebnim after 
passing through the internal capsule, in front of its knee. 

The functions of these accessory fibers are not positively 
determined. They unquestionably end within the substance 
of the medulla and pons, and, by their cerebral connections, 
serve to unite the cells of the cerebral cortex or of the basal 
ganglia with the cells of the gray masses of the pons. In 
this way they probably contribute to the mutual deperulence 
of the subordinate ganglia and those of the cerebrum, and 



274 



THE brain: 



probably help to bring the cerebmin into direct assodatM 
with the cerebellum and the nuclei of the cranial nerves. 

The longitudinal fibers of the pons are probably relat^i 
to or associated with fibers that leave the pyramidal tncB 
to join the cranial nerve nuclei. Starr found them wantiK 
in the microcephalic brain examined by him, as were al» 
the decussating and non-decussating fibers of the raphe c! 
the pons. This fact tends to confirm the view that the fibers 
of the raphe join the longitudinal fibers with the cranial 
nerve nuclei. 

Upward Continuation of the Fibers of the Anterioi 
Root Zones of the Spinal Cord. — It is difficalt to traw 
the course of these fibers in the medulla, because they are 
subdivided into small bundles by the arcoate fibers assisting 
to form the so-called '^/ormatio reticularis.''^ 



Internal Direct pynmldftl 
part odumns. 




Column of 
Bunlaob. 



Colamn of 
GolL 



Fio. 61. — A diagram dcstigiied hq the author to ahtnc the two fttbditi^iant, or 
tJie anterior root zones of the spinal cord. 



AVithin the spinal cord, the anterior root zones are 8ul»- 
divided by the anterior spinal nene roots (which travewe 
them to reach the anterior horns of the gray substance) into two 
distinct portions, an internal and an external (Pig. 61). Th« 



FIBERS OF ANTERIOR ROOT ZONES. 275 

^ ;, internal portion of each zone lies between the anterior spinal 
^ nerve roots and the column of Turck ; the external portion 
^ comprises the balance of the anterior root zone. Within the 
^ medulla, these two portions take a different course, so that 
':' each must be described separately. 

The interwil portion is first pushed to one side at the 
lower part of the medulla by the decussation of the crossed 
pyramidal tract. Above this level, where the olivary body 
becomes developed, its fibers appear to be thrust backward 
behind the pyramids and close to the median raphe of the 
medulla. At this level, the fibers of the origin of the hypo- 
glossal nerve separate it from the external portion. 

The so-called ^^ posterior longitudinal hundle^^ of each 
side (which has been described in previous pages that treat 
.of the crura cerebri) appears to be a direct continuation of 
the internal portion of the anterior root zone of the coi'd. 
Some of its fibers are apparently continued into the thalamus 
and thence into the lateral ventricle ; others seem to join the 
posterior commissure of the third ventricle. Like other 
bandies which lie close to the aqueduct of Sylvius, its fibers 
become medullated very early in the development of the 
brain of the human embryo. Those tracts of nerve fibers 
which surround it, and form the more superficial portions of 
the medulla, become medullated at a later period. 

The posterior longitudinal bundle and the round or soli- 
tary bundle, both of which bear intimate relationship with 
the nerve nuclei in the floor of the fourth ventricle, probably 
serve to connect these nuclei together and to place them under 
the control of the ganglia of the mesencephalon (Spitzka). 

The external portion of the anterior root zone (Fig. 01) 
enters into the formation of the longitudinal bundles of the 
reticular formation of the medulla. 

The changes which occur in the relative position of the 
anterior and posterior horns of the gray matter within the 
medulla (chiefly as a result of the formation of the fourth 
ventricle and the olivary bodies, in addition to the decussa- 
tion of the crossed pyramidal fibers) cause this tract of fibers 



?76 

to assnme different relatirjiis to adjacent parts tlmn arp rqn»] 
sented in the preceding diagram. 

If traced upwanl, this tract will be seen to lie beJtiful Qi\ 
olhary hody^ and to reach the surface of the mediilli,iib| 
lateral column. Internally, the fibers of origin of the snlMf I 
motor nenes bound it; posteriorly, it is lindted by p^f 
matter; and, externally, the nerv<^s <*f r?M» InferaJ muced<)[Q>{ 
tern are detected. 



.^.^^ 






Fig. 62, — A diafjrnm of thr riff fit i/t(rraf haff &/ a irwiMVtrat ^trfi, . ../ *}^ 
rolii, on a li-t'd with tlu oriffin of the fylh eranial nerrt, iMi>iiihL-i Nv \ 
from Erb.) 

Hr, root of trigerninua; V\ middli* Benaary nucleus of the trigemlatiB; V, 

elcua of eaiiie; tit, descemlmg rt)ot of sftmo; P, bundlei of the pjrminidat i , 

AcmBs; p, acci'&Sinj Wbcm vf ^&iue; Tr, Tr', iranFrerse fit»««r$« of U|« pom^ e«Mi^ 
tilling the " infddle pedundt' of the oen'ljelluni " ; R, r^ihte ; L, poeii^rior ht^B^ \ 
nnt fasciculyB ; ar\ &rca ocotipk'd bj the ext«^nia1 portioa of tiitisHor loae <f t 
ar, *rca occupied by iho internal portion of aa,mc. 

Within the substance of the pons ^ the interlacing ihh^m i*i 
that region lie immediately in front of this tracts 

When this tract reaches the cms cerebri^ it ia only sepi^ 
rated by the substania nigra from the '* cmsta cruris/' 

The for matio reticularis lies, within the substance of tb^j 
medulla, between the pyramidal tracts and the gray matte 



THE LEMNISCUS TRACTS. 277 

:t3i6 fourth ventricle, in a ventro-dorsad direction, and between 
the ascending root of the trigeminus nerve and the inter- 
olivary tract, in a lateral direction. 

In the region of the pons, the formatio reticularis lies be- 
tween the fillet (lemniscus) and the gray lining of the fourth 
ventricle in a vento-dorsad direction, and between the raphe 
and the external border of the pons, in a lateral direction. 

The view that the reticular formation serves as a channel 
for the transmission of the tactile sense and of pain sensa- 
tions to the cortex of the parietal lobes is supported by the 
late researches of Starr. Regarding the channel for the trans- 
mission of the sensations of temi)erature, no positive deduc- 
tions were established by these investigations ; although it is 
-well known that disturbances of pain and temi)erature sen- 
sations usually occur together. We are, therefore, justified 
in believing that they both travel along the same paths; 
until more is definitely established regarding temperature 
sensations. 

The Fillet. — This tract of fibers {lemniscus) has been 
already discussed in the pages devoted to the consideration of 
the crura cerebri. It springs apparently from the nuclei of 
the posterior columns of the opposed side of the cord, and 
ascends for a portion of its extent in front of the reticular 
formation (Fig. 63). It terminates apparently in the thala- 
mus and the inferior corpora quadrigemivAi, 

Some of these fibers are probably continuous with the 
anterior root zones of the corresponding half of the spinal 
cord, while others are connected with the nuclei of the pos- 
terior columns of the cord. Some authors describe this tract 
as consisting of two divisions in the region of the olivary 
body, an internal and an external. After that body has been 
passed, both of these divisions appear to join and to pass 
upward together behind the transverse fibers of the pons. 

The latest investigations respecting the lemniscus (Spitzka, 
Flechsig, and Starr) seem to warrant the conclusion that two 
sets of fibers are comprised within it ; one of which degener- 
ates downward and the other upward. About one half of it 



TUB BEAJK. 

appears to be associated in some way with the motor I 
aud the balance with the sensory tmcts, Fl- 
and Rohon have demoastmted this fact in ^J 

brains, and Spitzka has lately sastuined the cauxia vievkfj 
micioscopic investigations of a ca«e which bears dfrecilr t 
this tiekL The descending degeneintion of rl 

seems to confine itself to the inner half or two : f 

tract ; hence we may conclude that this portion of tbe I 
has a motor function,' The outer portion of the fiUfilJ 
pears to belong to the sensory tract ; since it 
upward and appartmtly extends to the region of the tha 
and the quadrigerainal bodies. This eoQclusion is in i 
with the views of many anatomists as well as with late i 
logical data. 

The peculiar course of the fillet tract in the medolkiii 
pons is made very apparent by cross-sections of the saoMfil 
different levels. In its lower part, this tract, after ]iartid|K^ ^ 
ingin the sensory decussation of the medulla^ occupies i 
that lies close to the raphe and nearly psirallel with 
interolivary tract). As it ascends, the libers of the tiUet 
come displaced, so that the long axis of the oval ai«a 
cupied by them within the upper part of the pons lies aeai^ 
at a right angle to the raphe, and in close relation to tki 
liymmidal tnicts. Spitzka comimres the outline of thi^s tniet^ 
cross-sections made through the mesencephalon immediate 
caudate of the lobes to the capital letter L — the exlreniid^ 
of the horizontal portion of each letter meeting the 
Certain fibers of the medulla that arise apijarenily frum thi 
clavate and triangular nuclei seem to pass across the medltt 
line (sensory decussation of the medulla) into the opposiM 
interolivary tract, and from that into the tract of the fillet 

Within the medulla, the so-called '* sensory tracts*' lliat 
carry impulses from the spiaal cord to the cerebrum pmb- 



> Spit7.kii ifl iuclmed to doubt the infallibiUtj ol ibe Uw of 
TIE., that it pfOi;reft?e? in the dippciloo of the cumjoW noraullx ooimfod tiy Ibe 
a« briiigs foririml of Ute tome itiuirosttiig cm««0 of aeooiMlarj tloeowtmaott Uujl 
to oppose tbo gcaermlJj tcoepled vi«w. 




THE TRACT OF THE FILLET. 279 

Sixably comprise the formatio reticularis, the larger part of the 
L //fillet, and the interolivary tract. The inferior cerebellar 
siijiedancles unquestionably transmit some forms of sensory 
i»i impulses to the cerebellum ; but it is still an open question 
^p: if other forms of sensations are not sent directly to the cere- 
(x brum without being first deflected into the cerebellum. 
r: The fillet is believed by some observers of note to send a 
j dip to the motor-oculi nerve. This seems to confirm the view 
[i of Stilling that the fillet is connected with the visual appara- 
• tus, since the optic and motor-oculi nerves are intimately 
J associated with each other, as is proved by the reflex move- 
, ments of the pupil. 

The reader is referred to previous pages for further infor- 
mation regarding the peculiarities of course exhibited by 
special fasciculi of the flllet, and some late views which have 
been advanced respecting its probable functions. 

The diagram which will be introduced later (Fig. 63) will 
help to render many points in the anatomy of the spinal 
cord and medulla more intelligible ; while its text will aid 
the reader in refreshing his memory as to other important 
details of construction of the higher ganglia and the cms 
cerebri. 

The fibers which cross the reticular formation in the dia- 
gram (F. R.) probably enter to a greater or less extent into its 
composition. 

The Direct Cerebellar 7Vac^«.— These columns of the spi- 
nal cord are shown in Fig. 52, and the fibers which compose 
them are depicted in a diagrammatic way in Figs. 63 and 64. 
Within the substance of the cord the sensory nerr^e roots 
probably communicate with these columns indirectly, i. e., 
through the vesicular columns of Clarke. In order to do so 
they i)ass chiefly between the bundles of the crossed pyram- 
idal column (Fig. 64, a). The fibers of the direct cerebellar 
tracts probably afford a direct communication between the 
gray matter of the 8ui)erior vermiform process of the cere- 
bellum and the cells of Clarke's vesicular column in the cord. 
They probably terminate in the cortex or central gray matter 




The horisontAl dotted HncM indicate the lirniti of the crtig, pons T&?oUl. tt&d OMdall^ I^ | 
oerebenum if ^epanitfd nifr'nttonrtlH fmm tho wr«l>min In oitlcr to hrioi; %htt 
cerebri and tubereu^' ni'oce. C. N., < 

corpus ^tri&tuni ; L. ^ BAtne; 0. T.^opCu*! 

ffraif matttr of the poti-^ Vim in; t, ii.,j'jrtiKiftfj reHetdarU ; Cf, D.^ «« 
of the cerebri hi ro ; 0.^ ofirnrt/ tt^nttf ; N. ('., H^mit* n.uet§u»\ T. N,, 
<Vrf« ; C* Q., forportt t/ufplnffrmhn : I. C.» i^omttK'iiPetnetit of the m>c»1W 
mptuU^* of the oerebnim ; m, motor cmttr$ Around the region of tlui %mmtf nl A» 
Undo: t, r., fibers of the *^ corona radiata " ; I, the thvn nf \hp !!o ealt^l *'^ y 
•t/rt^ Mic^/' fntm their oripin tn the motor otnUers of the f. r iferaiji^' 

lion in the ^nj^lion celU of the anlerinr honi» nf thit »\^iiin , :% ami HI 

ftbowin;: aTxo thcdecQSSAtionof the fi^ * modtiUA^tfaa^^i; 

X. S, nod 4. fibert cooncctin^ the ffr' ihm tcwtknl tttm^ 

tlic letiticul&r Diieletiit tad the cAudau .^ .^ ^ < ..^^ . ^. ..ic 





DIRECT CEREBELLAR TRACTS. 



881 



ptduHcIf^ passing to the cimdntc nucleus and the optic thakrous ; and 7» fibere con 
necting the gray substttncii uf the poos with the cerebellar cortex and the coq>u9 
dentatuiD ; 8, fibers joining the cei-ebellar cortex with the corpus dentatuni ; tf, and 
10, fibers connection the olivary body, with the eorjmb dentatom and the eereWUur 
«ortcx of the opposite side; 11, the srMialled ^^ direct renfnttar tnict^* of the spiual 
cord; 12, the tibers of the ''jillet traet^^^ eonnecting the oHvrtrv body with the thsda- 
ni«8 and tubcrcula quadrigcmlna — this imci is probably prolonged ecpbalad to the 
oerebnim and dorsad to the nuclei, T, N, and N. C* / 13, the ganfflion ceUt of tht an- 
ierior horn* connected with the "cr^wW ptfrnmidal tract ^' {e){ H, the same, con- 
nected with the ^''dir^H piframidal irrtei^^ {d}; 15, fibers of the eolvmn nf Burdtiefi^ 
tenninBting superiorly in the irianpilar nucleus (T. N,); Ifi, fiberfl of the (w/wmw of 
Ooll^ tenninating in the clavate nucleii!* (N. 1",) ; !7, spinal fil>ers entering the 
** reticular formation" directly; 18, fibers of the "inferior peduncle of the cere- 
bellum *' ; 19, paths for temperature and pain s;en«atioDii. 

of the worm of tht^ cerel>elhim. They reach the cerebellum 
by means of the iofenor ]>edimcle8 (processes e cerebeUo ad 
medallam — restiform bodies). According to Wernicke, the 
fibers of these colurans decussate after entering the superior 
vermiform process. 

The direct cerebellar colomns are considered l>y Meynert 
as a path for the transmission of sensory impulses. This 
view is strengthened bj^ the fact that the fibers of this tract 
arise from the cells of Clarke's column, whose connection 
with the iibers of the i>osterior or sensory spinal nerve roots 



AJ£F 



^Chik 



L^Cdl 



64. — A dioffram drmfpted ht^ the aultmr tn Ulwiirnfe tfif rrlative tUuati'm and funt- 
ihfMf OMocifttion of the dirret evrt^flhr coiumn *>/ the *pinaf <vrd, and t/ie vaticuiar 
eolumn of Clarke. 

C, vesoicular csolumn of Clurke ; n, fibers connecting it with the direct cerebellar column, 
paMing between the bundles of the cpos^sed pyramidal tmet. The other letter* o£ 
the diagram refer to the fissure, commissures, hom^, and the older subdivisions of the 
cord. (See prcTious tigures,) 



TffE BRA IX. 

has been positively demonstrated. They also 
tripetal degeneration aft^r lesions of the spinal conL 

The fact that Clarke's vesicalar colnmn i^ fonodoQlTij 
the spinal segments functionally associated with the 
and abdomen seems to warrant the belief that the dirwi i 
bellar tracts are in some way associated with the transi 
of visceral sensations from the thorax and abdomen 
the cord to the higher centers — probably the rei^b 
(Starr), 

CONTIXrATION FPWARD OF BnHDACIl's AND OoLI*S( 

FMxs, — These two columns, which compose a |>art at leitt^ 
the sensory or *' lesthesodic *' area of the spinal cord, are I 
to terminate apparently in the cells of two nnclei wUch i 
situated in the lower half of the medulla. That of GoU>< 
umn is called the ^^ekumle nucleus ^^"^ or nucleus 
that of Burdach's column the ^^triangulur nncltu^^ %yt\ 
cleus cuneatus (Fig. 53), The fibers are probably in terra j 
by the cells of the nuclei referred to. These fasciculi IB 
the t\ro nuclei which have been mentioned, and are inc 
in size by their interpolation, 

A tract known as the ^^ ascending root oftlicj^fth cron 
?i^roe,**and also one caUed the ^"^ fasciculus roiutidM^ \ 
formed by fibers apparently derived from the. posterior 
zones of the spinal cortl, which ha%e no apparent coimc 
with the two nuclei described above (Pig. 45), 

The fasciculus rofundus* has been named by Mejuert 

' The BO-callcd "mund^' or ^^soUtaiy^^ bundle of tlie inedtiHa hoj attnoiii tht rfM» 
Eioti of Clarke, Sdtling, Rrause, Meyn^rt, Spitzka, aod others. 

Kraiise lias named it the **^ respirator bundle/* from a ooxuiectioii wIiIqIi lit I 
CftH be demoDstratcd between it and the origin of the phrenic nerro id tbr cptel 
Spitzka rejects this view, and applies the name '* tri neural bundle ** to this tnet^ bi 
be beliere^ that it5 efferent fibers can be traced to three cranial Qerre», rta^ tlie I 
tenth, and eleventh. He conBidcrs it sl9 an '* aberrant ramns of the Qtoth p«lr,** mi 
tains the view advanced by Duval and Bigelow that iL^ cephalic end |Mui«ee SMolktl 
mediary nerve of Wrisberg, who$e function iei still in doubt, although it h I 
some to be connected with the gustatory aenBc The same anthor state* iluit, ia !• 
opinion^ the fibers of this bundle are dcHred from the opposite podterior colsom 0^ 1^ 
cord (that of GoU), or from the lemniscuB tract and the stratum tntermediniii. Ji mm^ 
to be positirely demonstrated that some fibern of the sensory tracts of th« »iH isUMi 
medullary decussation, analogous to that of the pyramidal libera, aa wm» 0iigjiMMf trf*^ 
Cftted by Mejnert 



^im 




THE SENSORY TRACTS. 288 

ays the ** ascending root of the lateral mixed system," and by 
J; Krause the " respiratory fascicle." It consists of fibers which 
p.. are disposed longitudinally, and which become detached from 
.,, the posterior root zone in the iipi)er part of the cervical re- 
^. gion of the spinal cord. 

The increased size of the fasciculus gracilis and the fas- 
' dcalus cuneatus within the medulla causes the posterior 
horn of the spinal gray matter to be displaced outward and 
forward, so that the continuation of the gelatinous sub- 
stance forms a collection of gray matter upon the lateral 
aspect of the medulla, designated as the ^^ tubercle of 
Rolando. ^ 

Tms Sensory Tracts.— The course of each of the sensory 
tracts in the mesencephalon is variously described by differ- 
ent observers of note. So wide are the variations in descrip- 
tion that it is impossible to bring all the published views into 
harmony. Starr has lately undertaken the task of collecting 
all the published autopsies that bear upon the solution of 
this diflBcult problem. He arrives at the conclusion that the 
views of Flechsig, based upon anatomical and embryological 
researches, are sustained by pathological investigation and 
also by an experiment lately made by Von Monakow after the 
method of 6\idden. He confirms this deduction also by a 
microscopical investigation of a microcephalic brain, in which 
all the motor tracts of the mesencephalon were wanting — thus 
affording an unusual opportunity for the study of the sen- 
sory tracts, ai)art from the motor. Tims he believes that the 
conclusions advanced by him are supported by four methods 
of research, each totally different from the other. 
This observer is led to the following conclusicms : 

1. That the outer part of the formatio reticularis and the 
interolivary tract (probably a part of the fillet) convi^y sensory 
impulses through the medulla. The root of the hypoglossal 
nerve divides the reticular formation of the medulla into an 
inner and outer portion. 

2. That the formatio reticularis and the fillet jwrform the 
same function in the pons. The fillet (lemniscus tract) is be- 



284 



THE BRA... 



Ueved by this observer to be associated with the »> 
*^ muscular sense." 

3. That the sensations of pain, toncfa, and temj 
travel along the f ormatlo reticularis to the cerebrum wiii 
decussation in the medulla and pons, because the iilien^^ 
nee ted with the transmission of such impulses hare 
sated completely within the substance of the cord. 

4. That the fibers which convey sensatioDB included i 
the term ** muscular sense" do not decussate in fhe 
They cross at the lower ]>art of the medulla, in the 
form decussation " of Spitzka, and pass upward lhrtMtgli< 
interolivary tract and the fillet of the opi>o6ite side. 
are thus conducted to the intemal capsule of the cerebr 

6. That all sensory impulses which are defected U> I 
cerebellum are destined to awake retlex action only. 

The fibers of the cuneate bundle, after they have U 
associated with the gray substance of the triangular niicli 
resolve themselves apparently into the so-cnlle<l **< 
flhernJ''* These pass forward and upward to the olivary 
of the same side, and therefore connect two nuclei 
medulla with each other/ 



1 If tbe mniii coltmins of the cord be tmced upward into the subtfUiMft «f tli* i 
thcj will be found to be related as- f ullow» : The anterior cohnaas (ftiooe of Tinfc>4 
tt\c croafied pyramidal columoa fonn the anteriar p^riumd» of Uie iii«ii«lhi ; ibi 
ooluinii* Are continuous with the reftlform body; the oolititnM of BufdMli wiA\ 
otmoBte bmidle; «od the columns of Got! with the proccanss gracOSft. 8|iltik« 
tlnl tlie fiberi of Burdnch'a oolumtia «rc omttiiiusd into thu rrstifona liodw {i^m 
deousntion and some directly,) as- arc thoce of the cerebellar tract ; mxnd that ^krf | 
to the ccrehcllar cortex. Tlie same* author states that the fibers of clie | 
oolumn arc traceable to the nucleus XastigU of th^ cerebellum, 

Starr b led to believe, from an analysis of collected eases of focal Ic^lofti vdbte Us 
niedalla and pons, that the fibers from the posterior columns of the aplmal eof^ fni* 
nblafly into the interolivary tract and the tcmnbcus. This author adv^ooos ma^ iHs^ 
arfurocnts in favor of the view that the acaisory tracta pan^s directly tlitoftgli iJ)« i 
pons, and ems without decussation or deflection Into the cerebellum, and that tlirr i 
quently reach the cnrcbral cortex by means of the intenuil cap^ide* 

Within the lower part of the medulla, the sensory traota (acoordlnfr t^ Starrt o 
^ three oolumna, cdled the funiculti0 gnicilia, the funicnkts cttr*> ' li^ f« 

•ticitlarls. and one tract which is the direct eontinuatjon of the d ^icller i 

of the oord* The oemree of sensory impulses ihmu^h the gny «il<iiM» b • i 
which diHerent opinlona are bold b; rariotiik ob^rvers. Dr. Starr Ine giTim an i 
summary of the views held upiin this fiibjeet in his late article on **The SenaQty TWt 
in the Central Kenroiia 9y«tem *' i^' JournAl of Mental and Nervous Dboayoa^^ Jnlj 



i^aiii 




JSENSOEY TRACTS OF MEDULLA. 



2S5 



The fibers of the fasciculus gracilis have probably a simi- 
lar continuarioij above the interpolation of its nucleus ; al- 
though some authors assert that a decussation of its libers 
can be demonstrated to exist. 

Some anatomists, among whom Meynert may be promi- 
nently mentioned, believe that a decussation of the sensory 
conduction paths takes place within the lower part of the 
medulla. The sensory libersj according to Meynert, issue 
from the triangular and clavate nuclei and piu'sue an arcuate 
course around the central gray column to reach the inter- 
oli^^ary tract, near to the mesial and posterior portion of the 
anterior pyramid of the opi>osite side. The view of Flechsig, 
however, that the arcuate fibers enter the substance of the 
olivary body of the same side, is the one most generally ac- 
cepted* The X)aths of sensory conduction will be discussed 
more fully lq connection witli the description of the spinal 
cord. 

The arcuate fibers of the medulla are divided into a super- 
ficial and a deep set. The fomier i3ass over the oliiary 
bodies, and lie near the anterior aspect of the meduUa, The 
deep set have been traced by some anthora to the cuneate 
bundle and fasciculus gracilis of the opposite side of the 
medulla, to the raphe of the medulla, and to the cells found 
in the nucleus of the restiform body. 

The arcuate fibers of the medulla probably belong to the 
eensory tracts. They B-ere found by StaiT to be normally 
developed in a microcephalic brain which lacked the motor 
tracts. 

The late paper by Sturr upon the sensory tract of the 

l^rontral nervous system* contains a collection of cases which 

seem to conflict with the deductions of Wernicke, Spitzka, 

and others, viz., that the sensory tract is to a great extent 

deflected from the medulla below the pons into the cerebel- 

Oiie difficulty tliat arises la that FtcK^hsig^a method of research ia iinBati 9 factory in the 
ktjD^iillo. Giiddeii*8 method haa b<-"eii MiecessfuUy triod in but one ia-'^tancc^ and inves- 
ItigAtlotia of microccphaljc brains have not yet been given much attention by ncurologifltB 
[ or ftoftlombt?. 

* "Journal of Nervous a»d Mental niaease«/' July, 1884. 
21 



THE BRAIN, 



lum, and that sensory impulses do not traverse the pons. 
Lesions of the pons are shown by this author to have resulted 
in marked disturbances of sensation of the opposite half of 
the body. lie draws the deduction that the sensory tract 
for each side of the body traverses the opposite half of the 
medulla and pons, and that no decussation of these tracts 
can be verified (by clinical data) between the sensory decus- 
sation at the lower limit of the medulla and the upper bor- 
der of the pons. Respecting the views of Wernicke and 
Spitzka, this author speaks as follows ; 

'^ It is very possible that some sensory impulses may pass 
to the cerebellum by the tmcts described by Wernicke and 
Spitzka, and, setting up there a reflex action, be the means of 
exciting that organ to do its reflex work. But, if so, these are 
not the sensory impulses which pass to the higher cortical 
cerebral centers, or w^hich are destined to awake in conscious- 
ness a perception of the sensation. The sensations which are 
perceived consciously are transmitted directly from the surface 
of the body through the spinal cord, medulla, and pons, into 
the internal capsule and thence to the cortical centers, and in 
their course undergo but one decussation. If that decussa- 
tion is complete in the cord, the tract remains on the same 
side from the cord to the capsule. If that decussation does 
not occur in the cord, it takes place in the sensory decussa- 
tion at the lower part of the medulla/ ' 

The Si pkr added White Substance of the Medulla 
AND Pons. — Under this head the fibers of the cerebellar pe- 
dundes may be considered. In previous pages the superior 
and middle peduncles of that ganglion have received due 
consideration, and the reader is referred to them for further 
information, as only the main points will be here touched 
upon. The inferior peduncles have, however, been incom- 
pletely described in previous pages, and therefore merit a 
more detailed description. 

T7ie Inferior Peduncles of the Cerebellum (processus e 
cei*ebello ad medullam). — If a cross-section of the medulla at 
the level of the apparent origin of the auditory nerve (Pig. 



4 



FIBERS OF RESTIFORM BODIES. 287 

pOT) be studied, two collections of fibers will be apparent in 
J,, the latero-posterior area of the section upon either side {ep 
' .and ip\ which together assist to form the inferior cerebellar 
^peduncle. 

The external division has been named by Stilling the 
^^restiform hody.^^ Its fibers, if traced from above down- 
ward, start apparently from the cortex of the cerebellum, 
and also from a layer of fibers surrounding the "corpus 
dentatum." As they descend toward the medulla^ these 
fibers are split up into two bundles by those of the ''direct 
cerebellar tract," which join the cerebellar cortex in the 
r^on of the worm. At birth, the fibers of the latter tract 
aze distinctly medullated, while the peduncular fibers are 
not, thus rendering the outline of the two sets very ap- 
parent. 

The fasciculi of the restiform body become ^^ arcuate 
Jlbers " within the medulla. These course first through the 
Bcxalled ^'zonular layer^^ in front of the olivary body ; then 
tbey reach the median raphe of the medulla by forming two 
bundles, one of which passes in front of and the other behind 
tbe anterior pyramid of the same side ; finally, they appear to 
cross the raphe, to terminate in the olivary body of th0 oppo- 
site side of the medulla. The fibers which cross in front of 
tbe pyramids are commonly knoi;ni as the "arciform fibers'* 
of the medulla. 

The raphe of the medulla and pons probably contributes 
fibers to the round or solitary bundle (trineural bundle of 
Spitzka), the i)Osterior longitudinal bundle, and the lemnis- 
cus or fillet tract. Fibers are also traced from it to the retic- 
ular field. These are believed by some authors to bear a rela- 
tionship to facial expression and to articulate speech. The 
superficial and deep arcuate fibers are also connected with 
the raphe. The raphe is crossed by the decussating fibers 
between the olives, and also by those constituting the '' pinni- 
form " decussation. 

The existence of an independent decussation of sensory 
fibers within the medulla, as well as those associated with 



THE BRAJX, 



motion^ has been apparently demons tra ted by the 
cephalic brain examined by Starr^ in which the pj 
tracts were wanting. It was found to lie upon the saaeWj 
as the decussation of the motor fibers. 

The interolivary tract contains Btranda, accordhig t^i 
investigations of the same author, that dei'elop boik 
below upward and from above downward. The aaiisocy] 
tion of this tract is in relation with the triangular and i 
nuclei. 

The internal dimsion Is described by Stilling as \ 
from the nuclei of the ventricular roof, and, after 
the medulla, as resolving itself into arcuate bundle;! 
become intermingled with the ascending fibers of Ihei 
rior root zone of the spinal cord, behind the olivary UAji 
the corresponding side. 

Some anatomists describe these arcuate fibers as ^ 
of being traced across the median raphe of the meduIK « 
into the olivary body of the opposite side. 

From what has been said, it will be appareni that 
olivary body of each half of the medulla* is a meiUtiiD^ 
communication between fibers which spring from tin? 
angular and clavate nuclei and those of the reslifonn 
ies and the remaining bundles of the inferior 
Bduncles, The physiological functions of the maan 

ly matter which are interpolated (the trian^lar 
clavate nuclei and the olivary bodies) are as yet some 
conjectural. 

Foctd lesions of the medulla, pons, or crus, are 
frequently of limited extent; but few cusen, howeve 
well adapted for anatomic4il deductions, Diseoaa of ^ 
basilar artery, resulting in thrombosis or apoplexy^ I9 Wf^ 
frequently the direct cause of lesions of the pons ; and ik 
motor .tracts (which lie ventrad of the sensory) are moi^ 
commonly affected by disease. Lesions of the dorsal ititf^ 
the pons are almost immediately fatal, fts centers of ihe paw* 



' The oHriry t^odj ( dentate bodj uf ibc m«4ulla) hu tvo acccftsnorr nwM 
irith it^ the BCM!«llod **aBtemai olivarif body ** mud ** inffffmi o&'mfry i«^ *< aC Miftttfl 



iJiii 




FIBERS OF RESTIFORM BODIES. 289 

Biaogastric nerves rarely escape injury. No disturbances of 

d^iensation are ever produced by lesions of the pons unless 

i^^hey are situated posterior to its deep transverse fibers (Starr). 

This feet points positively to the inference that the pyramidal 

jAaots and the gray matter of the pons are not concerned in 

jfjuiy way in the transmission of sensory impulses. That the 

-kgray matter of the ventricular floor of the medulla and pons 

jfbas nothing to do with sensation seems to be proved by the 

oases collected by Starr, where disease of the cranial nerve 

inndei failed to produce sensory symptoms in the body, 

Ledions of the gray matter of the fourth ventricle must 

first create pressure-effects upon adjacent parts in order 

to cause anaesthesia or other sensory symptoms below the 

liead« The opinion of Meynert that the descending root 

of the fifth cranial nerve decussates within the substance 

of the pons appears to be sustained by clinical statistics. 

Lesions affecting it produce ansesthesia of the opi)osed side 

of the face. 

According to the observations of Spitzka, the restiform 
body of either side may be regarded as composed of the fol- 
lowing parts : 1. The fibers of the direct cerebellar tract of 
the same side. 2. The decussating fibers of the opposite 
postero-extemal column of the cord, which have previously 
passed through the olivary body. 3. Some fibers of the pos- 
tero-extemal column of the same side. This author discards 
the fibers of Gk)ll's columns from participation in the cerebel- 
lar circuit. He believes that these fibers cross to the opposite 
side in the so-called sensory decussation of the medulla, and 
that they then pass directly upward through the posterior 
longitudinal fibers of the i)ons (stratum intermedium) to the 
posterior ]>art of the internal capsule of the cerebral hemi- 
sphere. 

This view is opposed to that of Starr, which has been pre- 
viously referred to, since it presupposes a double decussation 
of the sensory tracts, derived from Burdach's column between 
the spinal cord and the internal capsule— one in the medulla, 
and again by means of the middle or sui)erior cerebellar pe- 



290 TMB BEAfX, 

diiDcle. The deductions of Starr are baaed laigelr wn 
cliaical facts, supplemented by original research made ipi| 
a microcephalic brain, in which all the motor trucU ^•j 
wanting- 

The Middle Peduncle of tM CerebeUnm (procea»iidei»| 
bello ad pontum). — The fibers of this set arise from tbece»| 
bellar cortex and pass forward, both in front of and tl 
the substance of the you% eventually de<?iiasating with 
of the opposite cerebellar hemisphere in the median lint-, 
so doing, they assist in separating the fibers of the prr 
tract into distinct bundles, as is shown in previa- 
68). After crossing the median line, they Join u..,., .. 
of the gray matter of the pons. Here they probably hi 
associated with fibers which descend from the iBoer tMid^ 
the crusta cruris. 

These transverse fibers are wanting in animals whid < 
not possess cerebellar hemispheres. In previous pa^**, ili 
fibers have been discussed in detail. 

The Superior Peduncle of the CerebeUnm^ {proctasi^i 
cerebello ad cerebrum).— It is probable that most of the fib 
of this process are derived from the corpus den ta trim, 
decussate within the substance of the tegmentom cmrbi 
become more or less associated Tvith the celts of the 
niLcleus of the tegmentum of the opposite side. The 
distribution of these fibers is still a matter of dispuie^ 
authorities of note. Some believe that they paas to rhe upck 
thalamus ; others state that they pass to the cortex of tht 
cerebrum ; while a few think that they can be traced to tkt 
caudate and lenticular nuclei of the corpus striatum* TV 
functions which have been attributed to this proeees of ibt 
cerebellum have been alluded to in previous pages (whicli 
treat of the corpus striatum, the crus cerebri^ and the genenl 

t architecture of the nervous system of man) to which 
reader is referred for further information, 
froni 
brmd 



^ Th« thre* peduooki <d the oerTbi'lluin h%f^ b^en nMXcd hj Wilder wmA 8|pia 
from above downward, the ** pracp^danculus '* or " tf!>gin45oU bimciilmii,** t|ic ** |h 
brBcbium,** And Ibe ** pcksupeiluo cuius ** or " m^rvlg^brftcbiujiL** 



FUNCTIONS OF PONS VAROLII. 291 

THE FUNCTIONS OF THE PONS VAROLII AND THE DIAGNOSTIC 
SYMPTOMS OF LESIONS AFFECTING IT. 

The fibers that form the larger portion of this mass are 
J* abundantly supplied with gray matter, which seems to be 
ijj mixed throughout its interior. We may infer from this 
ri fact that they have some individual functions, in addition 
ir to being simply connecting commissures ; but what these 
1^ functions are it is difficult, at present, to positively state 
'« in every instance. 

j. Both the pons and crura cerebri are unquestionably con- 
^ nected in some way with the power of coordination of mus- 
^ cnlar movement, since injuries to either of them may result 
, in marked disorder of this function, and often in unnatural 
and forced movements. This function is probably associated 
with the fillet tract. 

The fact that some of the nerve fibers (probably those of 
the fifth and seventh pairs) decussate in these regions seems 
proven by clinical evidence, since lesions of the pons Varolii 
often produce paralysis of the facial nerve upon the same 
side as the lesion, while the opposite side of the body is af- 
fected below the face.' Crossed hemiansesthesia may also 
occur from a lesion in the sensory tracts of the pons (formatio 
reticularis). 

The facial nerve makes its exit from the side of the 
medulla oblongata ; some of its roots of origin can be traced 
as &r as the floor of the fourth ventricle, some come from the 
lower part of the medulla oblongata, while others descend 
from the upper border of the i)ons Varolii, and probably 
decussate. Now, a lesion existing in the lower half of the 

' A dm of paroljBia, where certain cranial nerves arc paralyzed on the same side 
as the existing lesion, while the body is rendered hcmiplegic on the opposite side, is 
«all " trfumed partU^ttM ** (the ** paralysie alteme '' of the French). It prci*cnts tevtmU 
typa depending upon the cranial nerre affected ; hence the so-called third nerre (motor- 
oculi) and body type, the fifth nenre (trigeminus) and body type, the seventh nerve 
(fadal) and body type. Professor Romberg, of Berlin, and Gubler, of Paris, have done 
to elucidate the clear appreciation of this complex form of paralysis and the 
I of lu production. They have been discussed in previous pages. 



a»s 



TffK BRAIN. 



--» 



V 



..^k 



_.^ 



pons Varolii will, therefore, produce a paralysis of lk(»| 
responding facial nerve and of the opi>o3it« spinal oatw 
whei^as, if it occur above the point of deenssation ii i* | 
encephalic fibei*s, the paralysis will be on the opposil« siit k I 

all parts of the body. T!m 

facts are shown in theart^ | 

panying diagram (1%. ^^ 

It is obvious^ fro© il 
study of this diagram, Mi 
a lesion of one latendUl] 
of the pons (at /) will 
paralysis either of niatoj 
or of sensibility of the o^] 
posite side of the body, \ 
of the corresponding sidt i 
the face; and that a 
of the hemisphere (il 
will produce paralysis 
the opposite fdde of 
face and body. 

As we might natimlif 
expect from the dbeelioi 
of the fibers of the puif 
Varolii, this portion of tb 
bmin acts as a direct ce^ 
ductor of both molar ibI 
sensory impres-sious frcio 
and to the cerebrum ; wkfle 
the collections of gray mat- 
ter within its snbdtanci 
prove it to possess iom 
functions of its own wUdl 
are independent of the stimulation of the cerebral cortex. 
Without entering into the different experiments which hatt 
been made to determine the exact part which this x^rdoa ol 
the brain plays in the complex machinery of movement and 
sensation, it seems probable that the pons Varolii i^gulaia 



H^i. 



FlO. 65. — A diagram to illttttmie the methnd 
of producfion of rroued paral^nM* ( A tter 
BammoDcl. ) 

c^ the left bcmisplicre; A, right hoTf of pons ; 
«, right half of medulla obloogata; d^ 
right half of spinal cord ; <?, right facial 
nerve \ /, fiber of origin from nucleus in 
medulla oblongata ; ^, descending fiber 
decufl?iatin!j; at upper border of pons ; A, 
Aflceadii^: fiber ; i, aensory root of spinal 
nerre ; A\ motor root of scosory nerve ; 
l^ lesion in pon^ ; m^ legion tn loft hemi* 
Bphere; n, paralyzed p.irt siippHed by 
facial nerve ; o, paral^ised part supplied 
by epinal nerve. 




FUNCTIONS OF PONS VAROLIL 298 

^or in some way modifies those automatic movements which 

jsigOTem station ^mdi progression. 

js The experiments of Vulpian and Longet also seem to sng- 

irgwt that the sensation of pain is x)^rceived by the pons 

i(t Varolii even when the cerebrum and the basal ganglia are 

jMriemoved. When these portions remain, such impulses are 

^ probably transmitted to the hemispheres as conscious sensa- 

^ Hens, and are there remembered. 

■. These views have been already discussed in connection 

^ with the functions of the corpora quadrigemina, to which the 

, Nader is referred. 

Oeneral convttZsions are peculiarly apt to accompany sud- 
denly developed lesions of the pons (such, for example, as 
embolism or a clot). These convulsions are generally followed 
by coma. 

The trigeminus nerve may be paralyzed by lesions of the 
pons, piX)vided the lesion lies within the inner two thirds 
of the reticular formation (according to the researches of 
Starr). If such a lesion be situated high up in the pons, 
trigeminal paralysis will coexist with hemiansesthesia of 
the opposed half of the body ; if situated low in the pons, 
the trigeminal paralysis and the hemiansesthesia will be 
upon the same side. The point of union of the ascending 
and descending roots of the fifth nerve is nearly at the 
level at which the fifth nerve escapes from the pons (line 
of Gubler). 

Difficulties of articulation are to be considered as espe- 
cially diagnostic of lesions of the pons or medulla, provided 
the presence of aphasia of cerebral origin can be excluded by 
the history of the case. There is unquestionably a tract of 
fibers (the motor speech tract) that serves to connect the nu- 
clei of the medulla with the cortical centers for the move- 
ments of the face and tongue. 

Cof^fugate deviation of the eyes may accompany a lesion 
of the pons. This symptom is not pathognomonic*, however, 
because it may occur also with cortical lesions of the cere- 
brum and lesions of the internal capsule. 



THE BMAUf. 



The motor ^ sevsory^ and Taso-TJiotor effects ut lesioiBitt 
in the pons tire mauifested in the extremities; chi»*fly*l« 
not exclusively, tii>oa the side opposed to the lesion. Tlibt 
not the ease with those erauial nerves whose fil>erft of t<M 
probably traverse the pons (the fif|h, sixths serenth, *ii:hrb 
eleventh [?], and tvs-elf th). The effects of in trapontin*? 
upon these nerves are modified by the seat of fhe h 
has been shown in preceding panigraphs. 

Cantraction of the pupils during an apoplectic? atUcfci 
to be regarded as strongly diagnostic of a clol within 
pons. 

Hmmorrhage into the pons is usually followed by 
and sudden death, if the clot be large, or if the blood 
into the fourth ventricle. The diagnostic points menti' 
above api)ly, therefore, more particularly to foci of 9otx% 
and destructive lesions of small size and slow derelo] 
When blood escaiies into the fourth ventricle, eonTnlsions 
observed, and death is liable to follow rapidly, 

Distiirhances of the circulatory and re/tpiratory fm 
tions may occur in connection with lesions of the pons 
they are to be regarded rather as evidences that the 
oblongata is directly implicated or subjected to pmssnrtL 

Deafness has been observed on the same side as the \fmf 
(according to Starr) in five out of twenty-six ea^es of reporiel 
lesions confined to the pons. The auditor}^ fibers have pwb- 
ably been severed on their passage to the nncleus of tk 
eighth nerve through the pons. 



FtJNCTIONS OF TME MEDULLA OBLONGATA. 






This ganglion— the uppermost portion of the spLaal 
— ^is the true nerf^e center of animal life ; since itnin^d: 
death is apt to follow severe or extensive injurj" to its wbi 
stance. The fact that the seventh, eighth, ninth, tenth, el«' 
enthj and twelfth neiTes arise directly from this ganglii 
and that some fibers from other of the remaining six crani 
nerves can be traced to the cavity of the medulla— the fo^ 



FUNCTIONS OF MEDULLA OBLONGATA. 296 

*i:ventricle — serves to explain the importance of this special 
32 nerve center to life. 

j' In addition to the special influence of the medulla oblon- 
r^i gata upon the nerves which arise from it, it contains also most 
*?• of the fibers which are distributed to the other parts of the 
w: encephalon, and thus it must transmit both the motor and 
l^ aensory impulses, as they pass from or enter the cerebrum. 

The medulla is possessed of a large amount of gray matter 
/ within its interior. It is by means of this gray matter that 
the action of the medulla, which is largely reflex in character, 
takes place. 

Prom the nerves which spring from its substance, we 
should expect that these reflex acts should be chiefly con- 
cerned in the movements of the facial muscles by means of 
the seventh nerve; with audition by means of the eighth; 
with deglutition by means of the ninth ; with respiration 
through the pneumogastric or tenth nerve ; with phonation 
and the action of the heart by means of the spinal accessory ; 
and with lingual movements by means of the hypoglossal. 

Various collections of gray matter in the floor of the fourth 
ventricle have been described in previous pages, as connected 
with special nerve roots. Experimental investigation has also 
determined that certain special physiological centers appar- 
ently have their seat within the substance of the medulla 
oblongata. 

The medulla, as a whole, serves (1) as a conductor of seTtr 
sory impressions^ which have passed along the sensory tracts 
of the cord upward to the cerebrum ; (2), as a conductor of 
wluniary motor impulses from the cerebrum to the spinal 
cord and its nerves ; (3), as a conductor of cerebellar motor 
impulses to the spinal cord and its nerves, in maintaining a 
tonic contraction of the skeletal muscles ; and (4) as an organ 
of automatic reflex action, governing all functions which are 
essential to life. 

The centers for special cranial nerve roots have been dis- 
cussed already at some length. A few imi)ortant deductions 
concerning them are suggested, however, by the periods of 



2B6 



THE BHAF^ 



life at which they are developed. It is now known X\xkiim 
are not all perfectly formed at the ex^>ii*ation of fa*til ft 
bat are perfected later, as rapidly as the requirainents <i[ tb 
body seem to demand- 

^he accessory nucleus qfthe hypofflosmtl nerve setaili 
be an additional structure, which is rendered nere^uri 
order to permit of the complicated mov^emenls Umt aati- 
manded in the pn:>duction of artwulate speech^ 

The dccessory facial nuclei are apparently deingaed •' 
enable the facial nerve to preside over the Tnorements wqat 
site to facial expression ; in contradistinction to tho^n 
ments that are essential to the functions of masticatioii 
respiration, which are probably controlled by the other m 
of that nerve* 

Two of the four acousfic nuclei are intimately bs 
with the inferior and middle peduncles of the cei^bell 
is reasonable, therefore, to infer that one of them^ at leasl^ii 
concerned in the transmission of impressions made upon At 
ear to the cerebellum. 

The importance of labyrinthine impulses as a factor in th 
control which the cerebellum seems to possess orer ojunb 
nated movements has been discussed in previous pagw. 

Among the i^pecial physiological centers of the medoBL 
the following may be proraiuently mentioned : 

L The respiratory center^ which governs the 
acts, in response to sensory impressions transmitted to it 
means of the centripetal fibers of the pneumo|rastric nHrri 
This center also presides over the acts of lau^hiuff^ *i/7- 
ing^ sobbing^ sneezing^ and hiccough^ which are jierfo 
by the muscles of respiration. It is excited by the UTitatkm 
of carbonic acid upon the terminal filaments of the pnenioo- 
gastric nerve in the lung, or by its presence in the blood. Aa 
excess of it increases the respirations, while on exee^ of 
gen tends to decrease their frequency, 

2, The vaso-motor center^ which seems to control the 
ber of the larger blood-vessels, by means of efferent iniim! 
tnmsmitted first down rhe spinal cord, next through t 



M^^m 



i 




PHYSIOLOOICAL CENTERS OF MEDULLA. 297 

rior Toots of the dorsal nerves, and then chiefly through the 
splanchnic nerves. They affect the muscular coat of the ves- 
sels of the thorax, abdomen, and pelvis. The upper limit of 
this center in the rabbit is placed by Owsjannikow (Ludwig's 
" Arbeitem," 1871) at about two mm. below the tubercula quad- 
rigemina, and its lower limit at about four or five mm. above 
the calamus scriptorius. Clarke locates it near to the origin 
of the facial nerve, and claims that large multipolar cells can 
be detected in the vaso-motor area ; while Dittmar (Ludwig's 
"Arbeitem," 1873) places it chiefly in the lateral columns, 
after the fibers have been given off to the decussating pyra- 
mids. Besides this vaso-motor center in the medulla oblon- 
gata, some parts of the spinal gray matter unquestionably 
exert a positive vaso-motor influence, causing constriction or 
dilatation of the blood-vessels. 

3. TJie Car diO' Inhibitory Center. — By it the heart is 
arrested in diastole, or held undey control, in response to 
sensory impressions carried to the medulla from other sources 
by means of sensory nerves. If the mesentery of a frog be 
exi)osed, and^ a slight tap be given it by the handle of the 
scalpel, the heart will at once cease to beat, but will soon re- 
sume its function. This experiment, coupled with many 
others of interest, seems to point definitely to the medulla as 
the seat of mediation between afferent sensory impulses and 
efferent inhibitory impulses upon the heart. 

4. The Center for Deglutition. — This controls both the 
second and third stages of that act, or from the time when 
the bolus passes the isthmus of the fauces. This subject will 
be found discussed, at some length, in the pages devoted to 
the mechanism of deglutition, as well as the movements of 
the oesophagus. 

6. The center for the mocemerUs of the oesophagus and 
the stomachy with its allied center for the control of the 
mechanism of the act of vomiting. 

6. The Diabetic Center. — This center, when stimulated, 
produces a saccharine condition of the urine. The diabetic 
center, as marked out by Eckhard, corresi)onds closely to 



TffE BBAIX. 



that defined by Owssjannikow as the vaso-motor aw^ 
ing of thb center in a well-fed rabbit T%ill prodrice ai 
erable amount of sugar in the urine, within an hcmr iirl 
following the experiment. This effect is poorly maiirii 
^nimals whose livers have been deprived of glyoopt I 
itanration. 

7. The Salivary Center. — This, npon excitation. *^'**^'^ 
increase the flow of the saliva, and possibly, also, il 

tic fluid and tli^ other digestive juices. The flow uf \ 
^apparently a i-eflex act dependent upon aflferent insj 
perceived through the gustatory branch of the fifth 
nerve, the eflferent impulse being transmitted by means of I 
chorda tyrajmni branch of the facial nenre, Ir is this fit 
tion of the latter nerve that is considered by some ]>hras 
gists as explanatory of the effect of the chorda upon i 
(See pages descriptive of the facial nerve aod its bnincbei) 

8. The convtdshe center, first described by Nothnaj^j 
probably associated in an imperfectly understood way 
the motor tracts that are found within the meduIkL III 
closely allied to the respiratory center, as is proved bf I 
convulsions which occur in consequence of carbonic-acid pci. 
souing, or when the supply of blood to the medulla is 
denly cut off after the ligation of a large vessel. 

9. A cardio-aeceltratory center^ which exercises the po»« 
increasing the frequency of the pulse by means of fibcp 

which jKiss downward into the cenical region of the spinal 
wrd ; they emerge to enter the inferior ceniral gnngtion d 
the sympathetic upon either side of the spinal column, theiKV 
poasing to the heart. 

By means of these physiological centers the medulla fa 
enabled to exercise a modifying or controlling influenc 
the more important organs of the body. In everj' ciisc^^ 
iaforaieil by exettar or centripetal nerre^ of the reqi 
of the various regions which are essential to the perfcimianc^ 
of their resjiective functions; and by mat^/r or centrtfugd 
nerfWy or, in 9i^me iastiuices, by its influence npon the 
i|f tk€ pa^o-m^tar sjfdem^ the projjer responses to thf 





KEnVOUS CI E CLE OF DEGLUTITION', 



299 



ppessions (telegraplied to it by the sensory Berves) are sent 

»out. This constitutes what is termed '' reflex aetion." 
In the second and third stages of the act of deglutition, 
for example, the medulla is thrown into excUatiau by means 
)f the following nerve-trunks : 

1, The branches of the trigemmus distributed to the 
palate, 
^ 2, The pharyngeal branches of the glosso - pharyngeal 
nerve. 

3. The oesophageal and superior laryngeal branches of the 
pneumogastric nerve, 
y Its motor responses are then made through the aid of the 
following nerves : 

1. Tlie pharyngeal branches of the pneumogastric, derived 

Cn the spinal accessory nerve. 
I, The hypoglossal nerve. 
J. The motor filaments of the inferior maxillary nerve, 
t. The facial nerve* 
5, Blanches of the cervical plexus, 
rhese centripetal and centrifugal sets of nerves, with the 
ailed "center" which intervenes, constitute collectively 
what has been termed the ^^ nervous circle^^ of the act of deg- 
lutUion, Similar ^'nervous circles" are associated with each 
of the more impfirtant funrtions that are of a purely reflex 
type, sneh as the act of respiration, the pulsation of the 
hearty etc. 

When the ganglia of the brain above the level of the me- 
dulla are all removed, animals will continue to live and 
breathe. Those regions which are supplied by the nerves 
that are associated with the gray nuclei of the medulla, as 
well as those supplied by the s]jinal nerves, will, however, 
still exhibit reflex phenomena when subjected to irritation. 
If the conjunctiva be touched, the eyelids will close. Con- 
traction of the muscles of the face, movements of the tongue, 
and twitching of the ears, can also be artificially produced 
by irritation of the sensory nerves distributed to those re- 
gions. 




300 



TUK BEAI2^\ 



In addition to these evidences of simple reflex letia 
more compliciited movements that i^eqnire eodrdinatim^ 
different sets of muscles can also be elicited. In m 
so mutilated, the acts of sucking and of degludticm tah 
performed with as great precision as in healthy These cub 
excited by the introduction of a moi^sel of foiKl Imett 
mouth 80 as to rest upon the back of the tongue, or tbeintf 
tion of a nipple between the lips of a younger aniimLL ^i 
also observe these phenomena in those rare caaes iif 
anencei>halic children, who nurse at the breast as 
as perfectly-developed offspring. 

The fact that a subsequent destruction of the nn 
causes instant annihilation of these reflex and 
movements seems to be a most positive proof that iha 
dulla can be regarded both as a center of reflex acttuii lal 
one also of coordination. 

Clinical evidences that the medulla acts as a 
center for the complex movements required in ariici 
speech are afforded in the disease known as **^fo#^. 
laryngeal paralysis^^^ first described by Duehenne^ 
hence often spoken of as '- Duchenne^s dnieaae*'' In thii 
dicion the nuclei of the medulla that are connected wiik 
hypoglossal facial, glosso-pharj-ngeal and npinal-i 
nerves undergo progressive degeneration ; hence, the tem 
^'bulbar paratysis^^ is often employed in place of th«otlia> 
previously mentioned. The effects of this degenemtioa m 
manifested in a gradual and progresisive paralysis of Ike 
toagQ0y lipSf palate, pharynx, and larynx, which renden a^ 
tiealatioQ, deglutition, and phonation more or less tmperfii^ 
mad at the same time causes an alteration in the nrjiii mini 
of the frice tliat is not easily mistaken. (See sabeeqoeit 
pugH^ ^.tt;..i. t«.*,|i more fidly of its symptoms.) 

Scttu^ . ^tes have advanced the view that the oU^vmr^ 

bodita are tb^ probable coordinating centers of artieisbUioiM 
bat tbfo appears to be an error, because those bodies an «mB 
tntfaiiilsly euaMcted with the inferior peduncles of tb^ eefS"^ 
bilhiia. A rasMirkable cam reported by Vulpian^ in 



^ms^ 




RESPIRATORY MECHAXTSM OF MEDULLA. 



301 



medu 



the olivary bodies were coTii|>letely degenemted, was found to 
exhibit no impairment of speech* 

The relation of the medulla to FAriAL expression is one 
of great interest, if it can be jxKsitively verified. Vulpian be- 
lieved that his experiments made ujxin the rat demonstrated 
the relation of all forms of emMional expression, sueli as cries 
and facial contortions^ with the centers of the medulla. These 
experiments have been differently interpreted, however, by 
some later investigators in the same line. Feirier thinks that 
the cry of animals which follows a painfnl impression made 
upon the extremities, after the encephalic centers above the 

^medulla have been removed, is to be regarded simply as a 
mety of respiration rather than an evidence of the sen- 
jn of pain^ — a view which is consistent with the chief 
fimction of that ganglion. This will now be separately con- 
sidered. 

y The RESPIRATORY MErHANisM is unqnestionaWy presided 
over by the medulla. Flourens ha^s devoted special attention 
toward the results of experiments, made upon the medulla of 

^.animals, in respect to their effects upon respiration* He 

;>laces its situation at the apex of the fourth ventricle near to 

le calamus scriptorius — a point which he terms the ''*' nasud- 

'mtair 

This center receives the following excitor or cenlripetal 
nerve fibers : 

^l. The pulmonary branches of the vagus nerve. 
2, The superior laryngeal branches of the vagus nerve. 
3. The sensory fibers of the trigeminus nerve. 
4. The nerves of general sensibility of the trunk and ex- 
mities. 
5. The sympathetic nerve. 
These various sources of sensory impressions enable the 
respiratory center of the medulla to so coordinate the muscles 
of respiration as to insure the proper performance and rela- 
tive frequency of the inspiratory and expiratory acts, as the 
amount of exercise and the demands of the body seem to 
mire. 



^ani 




)2 



TBE BBJUS, 



The nerves through which the oentiifagal or motrf i 
pulses are transmitted, in response to these aeiisorj i 
sions, may be thus enumerated ; 

1. The phrenic nerve, by fibers which Irarerse ibf ^^ 
cord as far as the level of the third dorsal nerves. 

2. The intercostal nerve.% which are given off ism\ 
dorsal region of the spinal cord, 

3. The facial ner\^e, which governs the movement!! o( \ 
nostrils during inspiration. 

4. The **xtemal branch of the spinal aceesaory 
which supplies the sternomastoid and trapeziosw 

6. The inferior laryngeal branch of the poeiim4 
nerve, which governs the movements of the g:lottia 

6. Filaments of the cervical plexus, whicli assist ihei 
nei muscles to fix the first rib during inspirarion* 

The respiratory act is vnder the control qf the w(U 
limited extent, in order to allow of speech^ vocalizalioo, i 
the expulsion of the contents of the uterus, bladder, audi 
turn. When this voluntary control is estrrie*! l)eyf>iid 
proper limits, it becomes lost, as the desire for nsxit 
becomes too great to be controlled. 

We have referred in a pi*evious page to the acts of < 
tiig, sf{/?n'nffj sobbing, laugh ing^ sneezing, and hiceau% 
modifications of the respiratcjry act. They are |ir^sidf«i 
by the respiratory center. 

The rhythmical alternation of expiratory and in^im 
woKicments is not due entirely to reflex action. The anic 
of carbonic acid in the blood modifies thi> action of Ibet 
spiratory center as well as 8en8f)ry imi)res8ions carried \f\ 
by means of nerves. This point has been previously tone 
upon. 

The course of the respiratory tract of nerre.^ will 
spinal cord has been made a subject of investigalinn by 
Vulpinn, Brown- S6quard, and others. The views of tl 
observers are somewhat contradictory. It la probable 
they run in the gray substance of the cord rather than in 
lateral columns, as Schiff was led to infer. 



CARDIAC CENTERS OF MEDULLA. 808 

i Long after the reflex excitability of the spinal cord has 
^f ceased, and even after all voluntary or conscious actions have 
been abolished, the respiratory center retains its activity. 
^ This is admirably demonstrated in the administration of anaes- 
^ thetics, which, when pushed to their fullest extent in animals, 
^ paralyze the brain and spinal cord before the respiratory cen- 
ters succumb. 
J-, The CARDIAC CENTERS withiu the substance of the medulla 
seem to be connected with nances which have opposite func- 
^ tions, one accelerating the pulse and the other inhibiting or 

xestraining the action of the heart. 

^ The rhythmical action of the heart is in no way connected 

1 with the centers of the medulla, as that organ will continue to 

\ beat long after it is completely severed from its connections 

with the brain or spinal cord. It seems to be controlled by 

; the ganglia of the heart itself (Bidder and Hemak's ganglia). 

The medulla appears to act simply as a governor of the heart's 

action. 

The inhibitory nerves connected with the cardio-inhibi- 
tory center pass from the medulla to the heart chiefly by 
means of the vagus ; hence, section of the vagus causes an 
acceleration of the heart's action, because it is no longer re- 
strained by these fibers. Powerful irritation of the sensory 
nerves of the stomach or intestine, the nostrils, or the larynx 
causes a stimulation of these fibers which may arrest the 
action of the heart. This may help to explain the fatal re- 
salts of a blow received upon the epigastric region, or the 
shock of a large draught of cold water or of an irritant poison 
upon the sensory nerves of the stomach (Ferrier). 

The acceleratory nerves connected with the cardio-accel- 
eratory center pass down the cervical region of the spinal 
cord, and escai)e to enter the inferior cenical or first dorsal 
ganglion of the sympathetic. From these ganglia they are 
prolonged to the heart, upon either side, as filaments of the 
cardiac nerves. Tliey can be reflexly excited by a stimulus 
applied to the sensory nerves distributed to the muscular 
system. Ferrier suggests that this fact may help to explain 



THE BBAJ.s. 



the rapidity of the heart's action during aclive msi 
exercise. 

The existence of a vasckmotor cbnter within the ha 
medulla, as has been proven to exist in animalss, is < 
by pathological obsen^ation. Subjective eensations of heili 
cold in the limbs have been fnnnd to exist in connectioti 
a lesion of the upper half of the medulla. The area' 
pied by this center in man therefore corre^pondjsi to tfctfl 
animals (aa determined by Foster), viz^^ slightly abc»?f ! 
calamus scriptorius. 

The vasomotor center vrirhin the sabstnuce of the i 
controls the innervation of blood-vessels. It is 
vrith afferent as well as efferent fibers. The fonoer 
rather to excite or depress the activity of rhij* cf>nter, and i 
in a reflex way to cause contmction or dilatation of the 1)1 
vessels. 

The vaso-motor nerves pass, by means of the snbsl 
the spinal cord, to various ganglia of the sympathetic sri 
and thence to the coats of the arteries. Tfiey tend tai 
tain a state of tonic contraction of the arterial walls, 
has been termed by physiologists ^* arterial t^jnv^,^ It 
been found that, when the spinal cord is divided 
the level of the medulla, this arterial tonu.«? is destroyiJ.1 
dilatation of the arteries immediately taking plac^, Ai 
tion of the sympathetic nerve or of cerebro-spinal 
which convey its fibers to certain blooil-vessels produr 
similar result, in regions more or less circumscribed ac 
to the nerve trunk vvliich is severed. 

The ** arterial tonus" is controlled, however, in part by tfc^ 
spinal cord, irrespective of the medulla oblongata, Thifl^bci 
was first pointed out by Vnlpian, who found that, after »• 
tion of the spinal cord below the medulla, a complelu de^itm^ 
tion of the cord or a division of the anterior s[itaal 
roots increased the dilatation of the blood-vessels. 

The vasomotor center of the medulla is stiniiihited byi 
rifation cf ami mnmrif nerre of the body, as is il rml 

by the general contraction of th(* blood •ve'isr 1m w 




VASO-MOTOR CENTER OF MEDULLA. 806 

It is somewhat remarkable, however, that along with this 
general excitation there appears to be a local diminution of 
the "arterial tonus," so that the blood-vessels of the part 
which is directly irritated become dilated and the skin mark- 
edly reddened. 

The activity of the vaso-motor center of the medulla ap- 
pears to be decreased when one of the branches of the pneu- 
mogastric nerve, which is sent to the heart, is irritated. This 
is described in a subsequent chapter as tlie ^^ depressor nerve?^ 
It tends to greatly diminish the blood-pressure by causing a 
oessation of the arterial tonus. Ferrier is inclined to believe 
that a distended state of the ventricles, when associated with 
a labored heart's action, creates a stimulation of this nerve 
and thus brings relief by inducing a dilated condition of the 
▼eesels and a diminution of the tension. 

The relations of the force of the heart-beat to the blood- 
pressure within the arteries seem to be governed by the vaso- 
motor center of the medulla and the nerve fibers associated 
with it. As the arteries contract, the blood-pressure necessa- 
rily rises and is then apparently compensated by a slowing 
of the action of the heart. On the other hand, when the 
arteries become excessively dilated, the blood-pressure falls 
and the heart is thrown into a state of increased activity. 

Again, the vaso-motor center and the center of respira- 
tion apparently exhibit reciprocal relaiions. During each 
inspiration, the pulse becomes somewhat accelerated; and, 
daring expiration, it is diminished in frequency. These 
oscillations are now believed to be independent of variations 
in the blood-pressure which are produced by the tendency 
toward a vacuum in the chest as the diaphragm descends. 

Perrier thus summarizes the reflex functions of the me- 
dulla : ** The medulla oblongata is thus a coordinating center 
of reflex actions essential to the maintenance of life. If all 
the centers above the medulla be removed, life may continue, 
the respiratory movements may go on with their accustomed 
rhythm, the heart may continue to beat, and the circulation be 
maintained ; the animal may swallow if food be introduced 



S06 



THE BBAnn 



into the mouth, may react to impressions made on its jensstjl 
nerves, withdrawing its limbs or making an irregnliLr^nsI 
if pinched, or even utter a cry as if in pain, and y 
merely a non-sentient, non-iutelligent, reflex m6€h2Liii.^u. 



DIAGNOSTIC SYMPTOMS OF LESIONS OF THE MEPHiA 
OBLONGATA. 

The size of this ganglion almost precludes the existew 
lesions, even if small, which do not inflnencTe to a grvsttr 
less extent the nerve nuclei contained within it. 

An implication of the cranial nei-ve-rt3ot.s (Figs, 'i^i hl. 
may cause disturbances of respiration, cirrnlnfiiin tibonatii 
deglutition, and articulation. 

The sensory and motor tracts to the extremltiea inaf 
simultaneously involved, and thus amesthesia i f) and paralj 
of motion may occur upon the side of the body oppii^ 
the lesion. The fillet tract may be also affected bv the l 
in which case evidences of unilateral ataxia wiU be devdi 
in the extremities. Finally, the lower part of the fan* 
be rendered paretic. 

Of the above-mentioned symptoms, aphonia and tlwii 
pairmeni of the respiratory and eirculaiory spmptonuw 
particularly diagnostic of raednllary lesions. 

The symptoms of Duchenne^^ disease ar^ i 
when chronic progressive degeneration of the n 
medulla exists. 

Suddenly deteloped lesions of the medulla ar^ liable 
cause instantaneous death. 

Diabetes and albuminuria may be excited by 1 
the medulla. 

When the pnenmogastric nerves are implicatcHi, dysj 
irregularity of the action of the heart, and ffasiric ar h 
tinal derangeinenis are encountered. 

In a few instances, tumors and foci of softening In the me- 
dulla have been known to exist and ci^eale no sj^mptonis oft 
diagnostic character. 




SYMPTOMS OF LESIOSS OF MEDULLA. 807 

Dysphasia^ and the loss of the power of protrusion of the 
tongue^ point to an implication of the hypoglossal and glosso- 
pharyngeal nuclei. 

A lesion of one anterior pyramid would cause a paralysis 
of motion in the opposite arm and leg. 

A lesion of both anterior pyramids^ or one in the median 
line of the medulla, so low as to involve the decussation of 
the '* crossed pyramidal tracts," would cause a paralysis of 
motion in both arms and both legs. 

A lesion of the lemniscus or fillet tracts in any part of its 
course, would create a unilateral loss of coordination of the 
upper and lower extremities of the opposite side. 

A lesion which involves the vaso-motor center of either 
side in the medulla would cause a general unilateral redness, 
abnormal heat, and profuse sweating on the same side of the 
body as the lesion. 

THE VENTRICLES OF THE BRAIN. 

The method of development of the brain teaches us that 
the cavities found within its substance are the evidences of its 
early tubular formation. The simplest forms of brains show 
that the primitive medullary tube becomes constricted in such 
a way as to form three vesicles, which go to form the cere- 
brum, the corpora quadrigemina, and the medulla oblongata 
of the human brain. In a general way, it may be said that 
the anterior vesicle subsequently develops, in the human 
subject, into the cerebral hemis])heres, the basal ganglia, the 
ol&ctory lobes, and the lateral and third ventricles.* The 
middle vesicle yields the cms of each hemisphere, as far as 
the pons Varolii and the aqueduct of Sylvius, or the commu- 
nicating passage between the third and fourth ventricles. The 
third vesicle forms the medulla oblongjita, the cavity of the 
fourth ventricle, the cerebellum, and the p<ms Varolii. The so- 
called "fifth ventricle" of descriptive anatomists can not prop 
erly be said to form a part of the primitive tube (Wilder). 

I Wilder appliei the term " ecduM ^ to the Tcntricular caviticB. 



808 



THE BBAI' 



The expansion of the anterior vesicle into the 

hemispheres, with its component ganglia and con 
fibers, causes each hemisphere, the cori3Us cullosutn, tl 
date nuclensof the corpus striatum, the fornix, and thet^* 
mus to assume an arch-like form, whose buttresses app 
each other in the region of the tloor of the emnjal cavity, 

Although the ventricles originally appear a> * 
ties in the process of development, they soon l>e* 
as to configuration by the development of adjacent struct 
In the fully foimed brain of the human subject the 
canal of the cord and its continuation into the mesenceii 
(the iter or '"aqueduct of Sylvius") remain tubular.. 
other expansions of the primitive tube ore more or 1 
fied, 

Pathologiciil changes are not infrequently observed 1 
ventricles, their size being often increased. In old ordeitk^ 
tated subjects the posterior corn ua of the lateral veniridesii* 
rendered funnel-shaped by the gravitation of the ceretn^^ 
spinal fluid, provided that a long- continued conlinemeal »o 
bed has been required. Flower has observed an ublitenit)* 
(more or less complete) of the hippocampus major from ite 
cause, accompanied by changes in the occipital lot>e8* 

The Lateral Ventricles.— These are two lar^ro carili* 
in the substance of the cerebrum, one in each hemispbAm 
They lie on a higher plane than the third ventricle, heiif 
roofed in by the corpus callosum. On the floor of each mif 
be seen the caudate nucleus of the cor])us striatum, the imt^ 
rior tubercle of the thalamus, the tffinia senucinnilanH s^fo- 
rating these ganglia, a portion of the fornix, and a plesra&^i 
vessels derived from the pia mater^ calle<l the **chorx>id pfc 
us/* Each lateral ventricle is lined with a delicate laj 
called the '^ ependf/jna^'*— that is, covered with cilia ia 
foBtus. From the central or main cavity of the latenil vent 
cle of each side three prolongations, called **corniia»'* are 
be observed. These are name<l from before backnurdt 
anterior, the middle or descending, and the posterior. Tte* 
lateral ventricles are separated from each uthtr by 




SM 



BHAiy: 



anterior pillars of the fornix (Fig. 07^ know^ as th^ 
minn of Monro, ^ In chrome hydrocejihaltLs when *fc 
tricles are excessively distended by lliiid. these ot • ' 
greatly enlarged, and may occasionally a<linit the 
linger. 

The anterior horn of eaeh lateral ventricle is produre:^ 
the development of the caudate nucleus. It cur^eii aro^fldii 
anterior extremity, and projects into the frontal lolie. 

The middle or descending Jiorn t^kes an irre^ilariy cmi 
conrse — compared by some anatomists to that of a lana^ 
—around the optic thalamus^ and extends intu the teapiP* 
sphenoidal lobe as far as its tip. On its floor may l*e fern 
eminence known as the ^^ hippocamptis major^^'^ whtrfa t 
nates in two or three finger-like processes, called lh^**j 
hippocampL'*^ The sharp edge of the fornix and a fold tjX 
choroid plexus may also be discerned here. 

The posterior horn is small and extends into the ocd] 
lobe. It contains, as in the case of the middle hom^ an 
tical elevation, called the ** hippocaviptis minor j^ BUti itd 
tated extremity, the '^pes accessorius.^ 

The ''calcarina" and ''collateral fissures** of the 
of the cerebrum are anatomically associated with the hi] 
campal eminences, as has been mentioned to a previous 

It may, perhaps, help the reader, in forming a proper 
ception of the relations of the Ten tricles to each other 
adjacent structures, to compare them to chambers in dUTi 
stories of a house* From such a homely simile the two laii 
and fifth ventricles might be compared to the attic c 
the third ventricle would be a chamber on the floor hel 
the fourth ventricle a room on a floor still lower down. 
lateral ventricle lies above the lecel of the basal ganfflia^ 
these ganglia appear to a slight extent upon its floor 
thu*d ventricle lies in the mesial plane of the brain, 
the optic thalamic mid extends dowJiward as Jar as the 
of the cerebrttm. Finally, the fourth ventricle lies in 
region of the medulla oblongata^ entirely below all rda 
with the cerebral hemispheres. 



RELATIONS OF THE VENTRICLES. 



811 



C5T Now, all of these cavities communicate and f onn in reality 

taa continuous cavity, with constrictions in caliber here and 

^there, and large expansions in other places. The cerebro- 




GmiaI of spinal oofd. 



spinal fluid is thus enabled to flow continuously from below 
upward till it fills the lateral ventricles, as well as the third 
and fourth, and to be forced out again when an excess of blood 
in the cerebral vessels demands a decrease of the intra- ven- 
tricular pressure. This subject will be more fully discussed 
in connection with the membranes of the spinal cord. 

The lateral ventricles are best exposed by separating the 
oeiebral hemispheres from each other, and then dividing the 
corpus callosum, upon either side of the median line, at the 
bottom of the great longitudinal fissure. The more important 
stroctures ui>on the floor of each can then be studied, and the 
position and general direction of the horns i>erceived. The 
middle and i)osterior horns can be subsequently laid open and 
studied separately. 



aiii 



THE BRAIN. 



The Third Ventricle.— In order to expose thh 
from above, the body of the fornix must be divided upm 
floor of the lateral ventricles and turned backward. 1! 
be done carefully, a vascular curtain roof (tha wki 
^'mlum mlrrpQgitum'^\ formed by the pia mater, wiH 
exposed. This will have to be divided also, before the ci^ 
of the ventricle is laid bare. 



AnHTulercle* 



peduncle of 
pinml gla^ 



Th 



sup. 



lamina } 
cinerea ) 



ThAnJ^ 



.10 



n 



12. 



15. 



<*-* I 



Tin. GT. — A diagram dmgmtd &y Ut0 ofOhor to §how lft# kmae ^nirfmm ^ Um% 
mut^ with the tubular graif maUtr rtmoiwly §koiHn^ tkt Ami wa 
arranpemmt of nnghboring potU. 

Th. Bup.^ superior part of thalarona ; Th. rat, mferior pftrt of «nric 
mbauru ; 1, section of opttc comtuissure; 2, inf undibttlin i 
anterior commiasuro of third Ycntnde; 4, miU^rior erua i 
dicans (in itti miliary tubercle); fi, bundle of Vieq d'Arrr ; 7 
cerebri; §, pora« Varolii; JU, posterior conimi.'<«tiru ; 11, c< ir 

aqueduct of Sylvius; 18, fourth ventHcle; H, third vcntnc . 
oompareii with Fig. 3^ in which the gmv lining of the ventricle ia inlact. 

This cavity is a narrow chink between the optic rl 
It is bridged across by three bands, called the anierior^ 
die, and posterior eommhntnres of the ventricle. The 
die or soft commissure is composed of grrtv tty.tt..*^ 



THE THIRD AND FOURTH VENTRI0LE8. 318 

jWiites the thaJami. It is often torn across in removing the 

-4min. 

. » 

If Posteriorly, the third ventricle unites with the fourth by 
...means of a narrow tubular canal, the " aqueduct of Sylvius " 
.(iter e tertio ad quartum ventriculum). This canal passes be- 
^.^neath the corpora quadrigemina, and may be regarded as a 
homologue of the central canal of the spinal cord, which has 
been exi)anded in the region of the fourth ventricle, in order 
to allow of the many nuclei of origin of the cranial nerves 
found in its floor. Anteriorly, the third ventricle communi- 
cates with the lateral ventricle of each hemisphere by the 
foramina of Monro. 

The third ventricle, the aqueduct of Sylvius, and the 
fourth ventricle are lined with a continuation of the gray 
matter that surrounds the central canal of the spinal cord, the 
00-called " central tvhular gray substance.^^ 

The relation of the third ventricle to the pillars of the for- 
nix, the lamina cinerea, and the structures that form the inter- 
peduncular space at the base of the cerebrum, are made very 
apparent in the preceding cut. 

The gray substance that lines the third ventricle has been 
described in connection with the thalamus, to which the reader 
is referred for information respecting it. 

The Pottrth Ventricle.— This cavity is properly regard- 
ed as an exjmnsion of the central canal of the spinal cord. It 
communicates with the third ventricle above, and the central 
canal of the cord and the subarachnoidean space below. The 
latter communication takes place through the " foramen of 
Magendie.^ It allows of the entrance and escape of cerebro- 
spinal fluid. The importance of this as a means of equalizing 
pressure upon the brain substance (when the vascular supply 
is increased or diminished) will be considered in detail in con- 
nection with the spinal meninges. 

The fourth ventricle lies below the level of the cerebral 
hemispheres. Its gray matter ccmtaina the nuclei of origin of 
the more important cranial nerves. These have been discussed 
in connection with the architecture of the medulla. Its roof 



S14 



THE BBAIX. 



is formed by the under surface of the cerebelluoi audi 
called *' valve of Vieussens," 



THE COMMISSUBES OF THE BRAIK 

In connection with the ventricle!?, the corpus call^ififfl 
lomix have been mentioned. They deserve further 
ation, as they have not been separalely described in \ 
pages. 

The CoRprs Callosfm.— This commis^uml band his 
discussed to some extent in those pages that treat of 
missural fibers of the cerebral hemispheres. It is al 
inches long by three quarters of an inch in breadtli^ sod 
at the bottom of the great longitudinal fissure. It is the 
commissural band between the hemispheres, and f(in»rti 
roof of the lateral ventricle of each, Aiif<?riorly, it cine 
downward to reach the base of the brain, and ijosterioriy* 
dips downward to form the "spleuiumr* The anterior bai 
is termed the ''genu " or ** anterior flexure '^ of the calktfUi^ 
The splenium reaches as far as the transverse fisstu^of ihi 
cerebrum, and bears intimate relationship with the pM 
gland and optic lobes. The so-caUed ** pedunclt^s of tte«t 
losum '' reach to the anterior perforated spaces at the lofit^t 
the cerebrum. Fibers of the callosum can !»** r?--!..*.! iq 
following parts : 

1. The white substance of the cerebral hemisphei 

2. The gyrus fomicatus, 

3. The fornix. 

4. The occipital lobe, 
6, The temporchsphenoidal lobe, along the d 

horn of the lateral ventricle. 

The fibers of the cmllosum are both longitudinal and ixtm 
verse. They serve to unite the component parts of the oew- 
bral hemispheres. The transverse fibers prol>ably assist h 
uniting homologous parts of each hemisphem. The fund 
of the longitudinal fibers is not well understood. 

The corpus callosum is sometimes defective or 




CORPUS CALL08UM AND FORNIX. 815 

KJ^When so, the septum lucidam and the fornix are also, as a 
rule, defective. The mental condition of subjects with a de- 
fective corpus callosum, according to the researches of Knox, 
is impaired in proportion to the imperfections found in it and 
B^the other commissural systems. Idiocy and imbecility have 
occurred as a consequence of this form of congenital deformity 
i.of the brain. The anterior commissure appears to be rela- 
. tlvely laige in those animals that have the corpus callosum 
imi>erfectly developed. It is possible that this band may 
.^ take the place of the corpus callosum in those rare cases 
" where that body is rudimentary or absent in man. Ward 
reports a remarkable observation ('' London Medical Gazette," 
ICarch, 1846), where the brain of a child of about one year of 
J age separated into two equal halves when it was removed 
\ from the skull, on account of the absence of all transverse 
commissural systems in the cerebrum and pons. 

The Fornix. — The arched fibers of this structure serve ap- 
parently to unite the*tip of each temporo-sphenoidal lobe with 
the thalamus of the corresponding hemisphere, and, by their 
fusion in the mesial plane, to join the two hemispheres with 
each other. Each lateral half of the fornix presents an an- 
terior pillar (which passes to the base of the brain and then 
doubles upon itself in order to unite with the thalamus (Fig. 
67), and a posterior pillar (which enters the middle or descend- 
ing horn of the lateral ventricle as a flattened ribbon-like 
tMUid, called the ^^ corpus fimbriatum"). This band termi- 
nates in the so-called ''corpus dentatum" of the descending 
horn. 

The arched fibers of each lateral half of the fornix become 
united with those of its fellow in the mesial line, thus forming 
the so-called '* body of the fornix." 

The body extends, anteriorly, from thie point of com- 
mencement of the anterior pillars of each side to that of the 
posterior piUars. It helps to form the roof of the third ven- 
tricle, lying above and in close contact with the reflection of 
the pia mater called the '* velum interpositum." It becomes 
fused posteriorly with the corpus callosum. The shape of 



316 



TMt liHAjy 



the body of the fornix Is triangular, the apex poindif In] 
ward* Its upper surface appaam npon the fltK>rof tliei 
cavity of the hiteral ventricle. In order to expi*!^^ \\»i 
ventricle of the cerebrum from above, it is necessary todinki 
the body of the fornix close to the anterior pillai^^ll 
turn it backward. The velum interpositnni mth its 
then conies into view. This membrane has to be also i%*liMfnl| 
before the ventricular cavity is seen. 

Commissures of the Third Vextricle. — ^The /wfewtl 
commissi/re of the thuxl ventricle has been considered in f^\ 
nection with the tegmentum cruris, and the anterhr ^ 
missure will be discussed in connection with the olfl 
nerves. The middle commissure is an integral part uf i 
thalami, which it serves to unite. 



THE MEMBRANES OF TITE BRAIN. 

The brain has three coverings, called, from wilboal i 
ward, the dura mater, the arachnoid, and the pia wv "^^ 
exterior, or rf//ra, is essentially protective in fiiiK: 
though it serves some other purposes, such as the tonm^ 
of venous channels, the support of certain parts, the dchj 
ment of the bones, etc. The arachnoid is a Hhm - 
brane, and is strurtunilly related tn the lymph * ...,....%) 
are all serous membranes. The pia is a vascular niembai 
and serves to nourish the parts with which it comes iac* 
tact. It will be necessary to consider each of these iim» 
branes separately. 

The DruA.— This is a dense fibrous membrane, clnodyi^ 
herent to the base of the skull and along most of the craawl 
sutures. It is loosely attached, however, U^ the convea 
the skull, save at the sutnrps. Small vessels paas fr 
exterior surface into the diploe, or middle layer of the I 
skull-cap. ItvS inner surface is smooth, and id Hneil w!tk 
pavement epithelium. It is in inflation to the so-eallecl **! 
duml space.'' Around the margins of the cranial fommtl 
the jietrosal ridges, and the crista-golli i>roce^s, the di 




THE CEREBRAL SINUSES. 317 

jiparticnlarly firm in its attachments. The '* sella turcica," 
tchat holds the pituitary body, is covered over by a process of 
Jthis membrane, which binds the pituitary body firmly in 
j>lace and conceals it from view. 

Processes of the Dura. — The dui-a assists to form three 
-jirocesses, called the cerebral falx, the cerebellar falx, and 
the tentorium. The falces of the cerebrum and cerebellum 
prevent lateral oscillation of the cerebral and cerebellar 
hemispheres, while the tentorium supports the posterior part 
of the cerebrum and prevents it from injuring the cerebellum 
by its weight. 

The Cerebral Sinuses. —Along the upper and lower bor- 
ders of the falx cerebri the two reduplicated layers of the 
dnra assist to form the superior and inferior longitudinal si- 
nuses. Where it joins the tentorium, the straight sinus is 
formed. The attachment of the tentorium to the skull forms 
the lateral sinuses, by splitting of the dura into two layers. 

The occipital sinuses run along the sides of the falx cere- 
belli. At the base of the skull we encounter the transverse 
and circular sinuses, both of which cross the median line, and 
also three pairs of sinuses, viz., the superior petrosal, the in- 
ferior petrosal, and the cavernous. 

There are some clinical suggestions of value that may be 
made in connection with the dura. Inflammatory affections 
of that membrane may induce thrombosis of the cerebral si- 
nuses, although that condition can occur also from extension 
of inflammation from other parts by means of the communi- 
cating veins, and as the result of pressure exerted ui)on them 
by intracranial lesions. The vessels of the dura may be the 
seat of extravasation of blood, and suppuration between the 
dura and the skull may follow traumatism. The nerves of 
the dura cause a headache, when that membrane is the seat 
of disease, or is pressed upcm ; as, for example, in the case of 
a cerebral tumor. Encephaloid cancer seems to occur most 
frequently in the dura about the foramen magnum. In this 
rase, the symptoms would be closely allied to those of a le- 
aion of the medulla. The communication between the cavem- 

28 



318 



THE BR.Uy, 



Oils sinus and the facial veins by means of the orbit explains 
the liability of patients siiEfering from a facial erysii^elas to 
a complicating meningitis. Leeching the nose will relieve 
headarhe, if congestive in type, because the longitudinal si- 
nuses communicate vrith the veins of the nose. Depletion 
back of the ears may also be employed to deplete the lateral 
sinus through the mastoid vein. The liability of suijpuration 
of the middle ear to a complicating meningitis is well I'ecog- 
ni^ed, and it is to be explained by the thinness of the bone 
between the dura and the tympanic cavity. As the sinuses 
of the brain receive tribntaiies from without chietiy through 
the sutures, the operation of trephining should never be per- 
formed over a suture if it can be avoided. Scalp- wounds are 
especially liable to become complicated by meningeal symp- 
toms from the venous anastomosis that exists between the ex- 
terior and the interior of the skulL The escape of cerebro- 
spinal fluid from the ear, in case of fracture of the base of 
the skull, is a valuable sign that the dura is lacerated in the 
internal auditory canal, and the tyuipauic cavity also in- 
volved. Displacement of the cerebro- spinal fluid from the 
subarachnoide^n space at the base of the skull by tumors of 
the dura or skull, the occurrence of meningeal hiemorrhage, 
severe concussion, etc, may tend to explain the occurrence of 
vertigo, nystagmus, noises in the ears, and some forms of pa- 
ralysis. This would be particularly the case if an excess of 
fluid were crowded into the cerebellar fossa. 

The Arachxoid.— Between the dura and the pia there 
may be demonstrated a delicate non- vascular membrane of 
the fibrous type, called *'the arachnoid/' It is continuous 
with the membrane, filling the same relative position within 
the spinal canal, known as the ''spinal arachnoid." It can 
be easily demonstrated by means of a blowpi])e, the injected 
air lifting it £ix>ra the pia. It forms sheaths for the cmoial 
nerves, embraces the basilar artery, bridges over the more im- 
portant sulci of the brain, cr>vers the exposed portion of the 
corpus callosum, and forms the limiting membrane for the 
IjTiiph-spaces of the more important vessels of the cranium. 



THE ARACHNOID AND PI A MATER. 319 

Between the arachnoid and the dura is a space, called 
;be ^^stbbdural space,^^ and between it and the pia is another 
ipace, known as the '' subarac/tnoldean space.^^ The latter 
JB traversed by a delicate network of fibers, that subdivide it 
.nto compartments. The subdural space is lined with an en- 
iothelinm. Both spaces are filled with a fluid that is similar 
to that which enters the ventricles by means of the foramen 
of Magendie. The normal quantity of this fluid that is found 
outside of the brain varies from a few drachms to about two 
ounces. Hilton compares this fluid at the base of the brain 
to a water-bed for protection against transmitted violence, as 
when a subject falls and strikes up<m the feet. The effect of 
any lesion that tends to decrease the cubical contents of the 
oranial cavity must be to displace this fluid. But, since the 
fluid is not evenly distributed over the base of the skull, 
some regions are more exempt from this displacement than 
otihers. Again, lesions of the character described may pre- 
vent the escape of the cei-ebro-spinal fluid through the aque- 
duct of Sylvius, and thus disturb the beautifully adjusted 
relationship between the amount of fluid within the ventricles 
and the circulatory appai-atus. Buret attributes the loss of 
eonsciausness that accompanies sudden lesions of the basal 
gpsiglin. or the white substance of the cerebral hemispheres to 
a zapid displacement of the cerebro-spinal fluid. Blachez 
nports a case where a rupture of the basilar artery filled the 
entire area of the base of the brain with blood (Allen). 

Thb Pia. — ^This is a fibro- vascular structure that lies in 
dfieot contact with the cortex of the brain. It is continuous 
wtth the pia of the spinal cord, but differs from it in that it 
ie more vascular and does not form ligaments. In the skull 
it eonsiBts of two layers, the outer being a receptacle of large 
Tanfinlnr trunks and the inner for the smaller twigs that enter 
die oortex. The inner layer is continuous with the neuroglia. 
nie pia sends prolongations into the ventricles of the brain, 
chiefly by means of the transvei-se fissure that lies between 
the cerebrum and the cerebellum. Allen states that it is so 
closely adapted to the walls of the fissure by which it enters 



»8f» 



THE HRAIlfT 



the Tentrirles as Xa resist the pressiirt» of the mrrtnn-ii 
flttid, and it thus prevents its escape from the ren- 

The prolongations of the pia within the sul>!<taii'^ 
brain constitute the parts known as the *M*c4um IntfrNl 
turn'' and the choroid plexuses. 

The relnm irderposUum has a triangular form aiid 
immediately beneath the fornix, and forms the ci 
roof of the third ventricle. Its base corresiKindi* to t\^ 
verse fissure, and its apex lies between Ihe foramifuif ' 
It incloses the pineal gland, and overlar>s the opti' 
TiBi'o large veins can be seen within its substanct* that 
into the straight vein of tlalen. It is rlo^ Intfri^^^t pn*lii! 
of the pia. 

The superior choroid plexuses are formed Intm thr 
eral margins of the velum interpositum and appear ia 
lateral ventricles. In each hemisphere the ch'^^-^^-i v\ 
the ventricle is prolonged into the middle or d» 
lying npon its floor. The vascular loojis that comp<^ 
plexus are covereti ^vith a layer of pavement er \m. 

In the third ventricle, two prolongations f, >., 
can be demonstrated. These am sometimes pn 1 
the fourth ventricle. 

The inferior clioroid plexus lies upon the fliior 4 * 
fourth ventricle (the posterior surface of the mednlbV ^ 
consists of a median tuft of vessels that envelops the indf 
surface of the worm of the cerebellum, and two lateral ]«> 
cesses that run out into the angles of the ventricle. H* 
plexus of vessels is generally derived directly from f^ '" 
which penetrates into the fourth ventricle tlLTough ' 
called ** inferior transverse fissure." This is sltnatM «l ttl^ 
line of junction of the under surface of the cert*1>ellitia vk 
the medulla. In this region, the amchnoid membmor ^ 
comes perfomted, forming the so-called ^' forumen of 
die,** through which the cerebro -spinal fluid i^aehes iht 
tricular cavities of the brain. 

The pia is supplied with nervoM from the thi 
seventh, eighth, and eleventh cranial nerves and 



ly. 



Mfiiiii wm 



THE CEREBRAL CIRCULATION. 321 

j^ympathetic system. Its blood-vessels are derived from the 
^./ertebral and internal carotid arteries. 

THE BLOOD-VESSELS OF THE BRAIN. 

The vessels of the brain are of great interest to the sur- 
''geon, because they have a direct bearing upon the pathology 
^and symptomatology of injuries of the head. To the gen- 
^^eral practitioner also the vessels of the encephalon furnish 
"^lany suggestions of value respecting those diseases that 
*«ttack the brain substance or the meninges. It is not out of 
^ place, therefore, to call attention to the more important facts 
^that have been published by those observers who have de- 
voted special care to the investigation of the anatomy of the 
veBsels of the brain and the peculiarities of its circulation. 
■ The blood is sent to the brain and its coverings chiefly by 
' means of two large trunks upon either side, the vertebral and 
' internal carotid.* The vertebi-als enter the skull by means of 
the foramen magnum and unite to form the basilar. The 
carotids enter farther forward, by means of the carotid canals 
in the petrous portion of each temporal bone. The branches 
that derive blood from the vertebrals are called, when col- 
lectively considered, the posterior or '"^vertebral systeifi." 
Those that spring from the carotids are called the anterior or 
** carotid system.^^ 

The "vertebral system" is distributed to the posterior 
portions of the cerebrum, the cerebral peduncle, the cere- 
bellum, pons, medulla, corpora quadrigemina, and the pos- 
terior part of tbe thalamus. 

The ** carotid system" is distributed to all the important 
parts of the cerebrum lying anterior to the cei-ebnd peduncle 
in the region of its base, the frontal lobes, the anterior and 
outer parts of the temporo-sphenoidal lobes, the insula, the 
two nuclei of the cori)us striatum, and the anterior portion of 
the thalamus. 

' The eorerlnffi of the bnUn derive blood from other BourcoH m well ; chiefly from 
IIm iDteriMl maiUUry, aioendiiig phArjmgeal, and occipital arteries. 



3M 



THE BEAIJi\ 



It will be necessary to consider the seixirate bnuirfie* 
the internal carotid, vertebral, and basilar arteries, in ^i 
to give the reader a clear conception of the aread ol ta 
tissue that are nourished by each. 

The mxERNAL CAROTID ARTERY, OH escaping from 
bony canal and entering the cavity of the skaU, rnmn ste 
upward and backward and gives oflF the following bi 
1, the ophthalmic ; 2, the anterior choroid ; 3, the 
cerebral ; 4, the middle cerebral ; and^ 5^ the posterior <* 
municating. 

The ophthalmic artery passes directly into th 
distributes its blood by many branches to the evf •aixi 
appendages. This fact enables the neurologist to defeni 
often, by means of the ophthalmoscope, the condition of 
cerebral vessels, because similar changes may be d 
the blood-vessels of the retina. 

The anterior choroid artery passes backward to the la 
verse fissure of the brain and assists in supplying the i 
sels of the choroid plexus. It lies in relation with iht 
treraity of the temporo-sphenoidal lobe, which concfdi 
from view for a part of its course. 

The anterior cerebral artery winds around the edge of 
optic chiasm and meets its fellow about one twelfth uf 
inch in front of the chiasm, where the two become jnli 
by a short branch, the anterior communicating artery, ft 
this point the two vessels run side by side, foUowin; 
curve of the corpus callosum from its beak to its postd 
extremity. This vessel supplies the optic rhiasm, the 
cinerea, the anterior portirm of the caudate nuel 
corpus callosum and the adjacent fornix, and the too" 
tions upon the inner surface of the hemisphere of the 
side, as far as the cuneus. The importance of the rel 
this vessel to the edge of the optic chiasm, as a factor 
production of that rare condition known as *'bi*tein 
hemianopsia" has been shown in a i)aper by Prot 
Kmipp, of this city. This condition is discussed hiler 
the volume. 



■Ma 



THE CEREBRAL CIRCULATION. 823 

I The middle cerebral artery is especially important, be- 
iCaiise it is now known to supply the so-called' '' motor area" 
.of the cerebral cortex. On leaving the internal carotid trunk, 
it crosses the anterior perforated space and enters the Syl- 
vian fissure. Here it gives oflf its main branches, which are 
nsaally four in number. All along its upper surface, how- 
ever, small arterial twigs are given oflf in the Sylvian fissure 
and in the neighborhood of the anterior perforated space. 
Tliese enter the substance of the brain and supply the cau- 
date and lenticular nuclei of the corpus striatum and the 
internal and external capsule. Its main branches take dif- 
ferent directions. One runs forward into the convolutions of 
the frontal lobe, one backward as far as the extremity of the 
horizontal limb of the Sylvian fissure, and two pass upward 
on either side of Rolando's fissure as far as the upper frontal 
and parietal gyri, that lie adjacent to the great longitudinal 
fissure. Thus it appears that the basal ganglion which are 
connected with motion derive their blood-supply from this ves- 
sel, as do also the island of Reil (the insula) and the convolu- 
tions that bound the fissure of Rolando and the Sylvian 
fissure. Embolism or thrombosis of the main trunk causes a 
hemiplegia of the opposite side of the body and motor 
apliasia, because the motor gyri and Broca's center of articu- 
late speech are deprived of blood. Should some one of its 
branches alone be occluded and the main trunk escai)e, these 
symptoms would be modified. The middle cerebral artery of 
the left side is the most common seat of embolism, because 
that artery is the terminal branch of a direct line of vessels 
arising from the arch of the aorta in such a way as to favor 
the entrance of floating particles in the blood into the mouth 
of the left common carotid artery. 

The posterior communicating artery connects the internal 
carotid with the posterior cerebral, and thus establishes the 
vascular circle at the base of the brain known as the '' circle 
of Willis." It gives oflf branches that supply the tuber 
cineream, the corpora mamillaria, the optic tracts, and the 
inner surface of the thalamus (Westbrook). 



THE BiiJJN. 



ThovEUTEBRAL ARTERIES of either sitle tmite toformt 
basilar. This tessel gives off the i>osterior c* 
at its anterior extremity, and thus as.'dstd tol.*.,. * 
of Willis. Along irs side.s, transverse branches are 
off. One of these, the auditory artery, supplies tir 
mechanism. 

The posterior cere^bral artery SLTises from the am 
tremity of the basilar and passes outwaxd and bie 
around the crus cerebri to reach the temporal and « 
lobes of the cerebrum. It follows the coui'se of the cal 
fissui*e (Westbrook). As it crosses the i>o8terior [ler 
space, small arterial twigs escape and enter the sub^tai^j 
the brain to supply the thalamus. A posietior 
branch is sometimes given off. This assists to form the \ 
interpositum and the choroid plexus, and giires off 
to the pineal gland and optic lobes. The main trunk j 
posterior cerebral artery supplies the eras cerebri, optic 
and geniculate bodies. 

The basal ganglia of the cerebrum derive their vj 
supply from twigs that arise from the vessels compc^sjiigil 
circle of Willis. Buret has observed the circular outJlue^ 
these ganglionic twigs. In a diagram designed by W« 
brook/ the basal gtmglia have been projected^ as it 
upon the surface of the cerebrum. The outer limit d 
ganglionic masses constitutes almost a perfeet circle 
quote the author of the cut, ''The diagram was obtained 
making a horizontal section of a cerebrum, low enough to > 
the lenticular nucleus, and then perforating the brain m\ 
styles so as to mark out the limits of the ganglia* 

As regards the distribution of arteries within the br 
substance, some pmctical discoverie.s liave been made. D« 
fuuDd that injections of individual ti*unks distributed 
cerebnil cortex passed over to a slight extent into 
plied by other vessels. He drew the conclusion ttom 
fact that a collateral circulation did exist between Fe?»eb( 
large size, not only at the base of the brain but also upon 

* ** Anaals of Anatomy mad Sui^gQi;^*** vol Vu 



THE CEREBRAL CIRCULATION. 323 

^fSnifaoe of the cerebral hemispheres. The vessels that run 

^fOver the surface of the hemispheres in the meshes of the pia 

^jigive off arterial twigs that everywhere dip into the cortex 

^ and penetrate its layers. These are subsequently prolonged 

-.J into the medullary substance of the hemispheres. It seems 

probable that the nutrient vessels of the cortex do not anasto- 

, mose with each other or with those that enter the brain sub- 

^, stance from the region of its base. Westbrook claims, as a 

zesalt of special researches, that a portion of the centrum 

. ovale of the hemispheres is destitute of vessels. 

The vessels of the ventricles are derived from the choroid 
, plexuses and the velum interpositum. Some twigs are given 
off from the latter of these sources to the thalami and the 
commissures of the third ventricle, and also to the caudate 
nuclei of the corpora striata. According to Duret, these 
sometimes anastomose with the branches of the middle cere- 
brals given off in the Sylvian fissures. 

The choroid plexuses do not appear to nourish the brain 
sabstance or its ganglia, but are destined rather to assist in 
the secretion of the ventricular fluid. They derive blood 
from the anterior and posterior choroid vessels. 



THE CRAOTAL NERVES. 

THEIR ANATOMY, PHYSIOLOQY, AND CLINICAL VALUE. 



THE CRANIAL JS^ERVES. 

THEIR ANATOMY, PHYSIOLOGY, AND CLINICAL VALUE. 



THE CRANIAL NEEYES. 



In the previous chapter many points pertaining to the 
superficial and deep attachments of the cranial nerves have 
been incidentally mentioned whenever different regions of the 
brain from which tliey arise have been considered. The nu- 
clei of origin of some of the nerves have been discussed in 
detail. It seems to me advisable, however, to call attention 
again to some scattered hints, which have been dropped re- 
specting these nerves, before they are individually considered 
from a physiological and clinical standpoint. 

The nerves which arise from the brain are arranged as 
twelve pairs (according to Soemmering), which, from before 
backward, are called the olfactory, optic, motor-oculi, troch- 
learis, trigeminus, abducens, facial, auditory, glosso-pharyn- 
geal, pneumogastric, spinal accessory, and hypoglossal. All 
of these, excepting the ninth, tenth, and eleventh pairs, are 
confined in their distribution to the head; while the other 
three have a distribution to the stnictures of the neck and 
trunk. 

Willis has divided the cranial nerves into nine pairs, 
grouping the seventh and eighth nerves as one pair, and the 
ninth, tenth, and eleventh as one pair. 

The OLFACTORY TRACT AND BULB must b(» H^gjirded in the 
light of a constituent part of the brain rather than as a true 
nerve. This is demonstrated by its method of development, 
as well as by certain i)eculiarities in its structure. During 
foetal life the olfactory lohe or tract consists of a diverticu- 



330 



THE CRANIAL NEBVBS. 



lum from the hollow globe of the cerebral beioisiihere. oBdnl 
cavity then comnmnicates with the latenil ventrici**. Ibe^f 
tical layer is continuoTis superiorly ^ith that of tli*^ rv^ ci^ 
the brain. 

The olfactory bulb forms a cap which embrace?! tiie |i 
longation of the brain substance. In its int-erior, 
masses—the so-called ** glomeruli'' of the sf rat urn yl 
sum—SLTe found. These are peculiar to this region. 



I"v 



iJT 



^m\ 



Tin 



Fio. 68« — The ban of the ihtll and ikf anmiat HcrvM. 

t nerrcB are indicated by Roman numomlB: 1, ntUchmiaiit of the teatorina; %i 
toroica ; 8, carotid artery. 



Each olfactory nerve fiber appears to be wonnd iiito i 
knot, as it were, by the aid of nerve cells that are iiisertf?d b_ 
its course* The cortical substance of the olfactory tiart 
lobe presents, moreover, peculiarities in respect to the 
which eumiKJse it. These are in marked contrast to tl 
which compose the cerebml cortex. 



DEEP ORIGIN OF OLFACTORY FIBERS. 331 

gr The olfactory nerve has three i)eduncles or roots by means 
^ of which its fibers find their deep origins within the brain 
.;■ Bubstance. The external or long root passes along the front 
border of the anterior perforated space, and enters the tem- 
. I)oro-sphenoidal lobe. The middle or gray root arises from 
^. the cortical gray matter covering the anterior perforated 
si>ace. The internal root passes into the substance of the 
.. frontal lobe. 

The view is held, from some results obtained by Gud- 
den's method, that the olfactory sense is presided over by 
a center or nucleus which is situated in the substance of 
the temporO'SphenoidaZ lobe^ and that decussating fibers can 
be proven to pass between the olfactory tracts and also be- 
tween the centers of smell of each hemisphere. The diagram 
introduced (Fig. 69) will help to illustrate in a rough way the 
conclusions advanced by late observers. 

When the optic thalamus was under consideration, the 
opinion of Luys, that a center of smell could also be demon- 
strated within the substance of that ganglion, was commented 
upon. Some pathological facts, ad well as clinical experi- 
mentation (to which that author refers), appear to lend cre- 
dence to the view that the optic thalamus is associated, to a 
greater or less extent, with the special senses of smell, sight, 
and hearing. Its anatomical connections with this special 
sense are, however, a subject of pure conjecture as yet. Gud- 
den's method of research does not sustain the opinion of 
Luys. 

The late investigations of Flechsig have led him to the 
conclusion that the olfactory tracts can be traced backward as 
three bundles. One of these passes to the base of the frontal 
lobe, and probably terminates in the gyrus fomicatus; one 
. goes to the cortex of the gyrus uncinatus ; and one can be 
traced to the internal cajpsule of the cerebrum, by means of 
the anterior jwrf orated lamina. Ganser and Gudden (by 
means of the latter^s method of observing the atrophic changes 
that follow the extirpation of certain parts in the newly -bom 
rabbit) seem to have arrived at the conclusion that the ^'olfac- 



332 



THE CRANIAL KERVE8. 



tory portion '' of the anterior commissure of th^ brain coniMfa 
the two bulbs of the olfeetory nenres, and the so-called "t» 
poral portion " of the anterior commissure connects the t» | 
I>oral lobes of the two hemispheres. 







Oifkctory 
Centre 



Oi£MfSt4>ry 
Cantjro 



Fig. CO. — A dioijram (ksiffnul hu (he author to illustrate the probable denuta^'ion r '' tJ' 
^fibrrs of tlvc olfactory traeU, 

O. B., olfactory bin>>: O. T., olfactory tracts; 1,2,8, internal, middle, and fxtcni 
roots of sumo ; C. S., corpus striatum of each hemisphere of the cerebrum; a, fben 
connectincT the olfactory tract.s ; 6, fibers connecting the centers of smell* «-^, W 

rior commissure, with its two sets of fibers. 



The fact that the so-called anterior commissure of the 
brain consists of two strands (the temi)oral and olfactory 
fasciculi of Ganser) is not new. It is only the verification of 
tlie view that the olfactory apparatus can be proven to have 
an anatomical relationship with the anterior commissnre thai 
deserves special notice. In man and the monkey tribe, the 
temporal fasciculus is much larger than the olfactorj-. In the 
lower mammals (particularly in the rabbit, henlgehog, and 
mole), the olfactory strand seems to be developed in excess of 
the temponil. 

The fibers of the optk^ nkuvp: have been already consid- 
ered at some length when the cori)ora quadrigemina were 



DEEP ORIGIN OF OPTIC FIBERS. 



333 



•• under discussion. The reader is referred, therefore, to pre- 
'- vioas i)ages for information, which it is unnecessary to repeat 
^ ' here. The admirable diagrams designed by Munk to illus- 
trate his views respecting the areas of vision within the cortex 
of the occipital lobes will possibly prove of value, in connec- 
tion with others which have been designed by the author to 
show the general relations of the optic fibers to different parts 
V of the brain (Figs. 42, 43, 44, and 73). 




FiGR. 70 and 'JX.— The vimuoI tradn, (Munk.) 

A, Tirail Area of right occipital lobe (dotted); a, same of left 8ide (lined); R,r, retinn 
(right and left); B, areait of hearing, contiguou(« to the visual an'os; Ch, optic 
cfaiaaiD. Thid figure may be contrasted with Fig. 43. 

The optic nerves will be separately described in subse- 
quent pages, and many points of clinical interest will be 
mentioned in connection ^ith them. The deep origin of 
the optic fibers is as yet a matter of dispute among authors 
of note. 

84 



S84 



THE CIUmAL JfJ^JSrjSSL 




The sujyenoT corpara quadriffemina^ the pnlThmr ^i fM 
optic thalamus^ and the external ffeniculai^ bodies aut » 
questionably parts of the optic apparatus. Tf '' i 

ably connected also to some extent with the \. . .n : - 

Certain convolutions of the cerebral cortex (probttbly tJiMe^ 
the occipital lobes) are concerned, moreover. In the oausdm 
I>erception of retinal impressions (see puffe ISO)* The tm^ 
bellum is supposed also to receive afferent lil^^ 
organ of sight* 

Munk believes that in the dog three distinct viaii 
in the retina correspond to three ** visual spheres^ in 
tex of the occipital lobe of the brain. The exiemai 
each retina is connected with the external part of the < 
visual area of the corresponding cerebrxil hemiJiiphere ; 
the central and internal portions are connected wit 
sponding parts of the cortical visual area of the op| 
bral hemisphere. 

In connection with experiments, made to deti 
arrangement of the optic nerve libers in the chiasm 
their relation to the various ganglia of the Ir * 
claims to have demonstrated that a band of fiber 
in the optic tract and doeely intermingled vnth it^ 
do not degenerate when the eyeballs of a young 
extirpated. He applies the term ^Hf\feri€^ cerebt 
musure^ to thi^ band^ and bdierea that it serves as \ 
commissure between the opdc thalamic He found tl 
remained unchanged even after the opdc lobes and lh<?| 
nienlate bodies were d»troyed : hence he concludm 
is in no wise Msodated with the visual sense. 

Respecting the question of decu^ation ^ tkt 
Jlher^ ll» snme ohmrw has arriTed at the foUowtog 
dushuis: 

1. Tliat a compfeie dwQSsatioa takes place in Uiei 
^ Ike binl ^leiiM. 

Sl That xht OtfCMMlioB ts only partial in the higher i 
SMilia. althiMM:h Ihe pi\>pcirtioa of the deeossating fiben^ 
dit no»4^<^i!WtHini b sab|ec« to rarialians* 





ARRAKQEMENT OF OPTIO FIBERS, 336 

3. The direct bundle does not occupy the same relative 
position in the optic tract in nil mammalia. 

4. Tliat semi -decussation exists in all animals possessing 
binocular vision. Total decussation accompanies monocular 
vision only, 

6- That there does not exist any ^' inter-retinal bundle," 
as claimed by some observers. 

6, That three sets of fibers exist in the optic system of 
mammals: (a) The optic libera, which are both crossed and 
direct ; (fi) the fibei"s of the inferior cerebral commissure ; (c) 
certain ^^hemispheric fibers,'^ n^hose course and temiinations 
are not, as yet, definitely determined. 




Fm. 72. — 71^* normal ttisual fiM 

The field is marked off in deg^efl» flo that a drawing of the vienal field of an? individual 
patient by incuDS of a perimeter may be compared, when dwmed abnormal. 



Ganser has lately published a confirmation of Gudden's 
experiments and conclusions dniwn from the rtibbit, by a 
similar set of experiments made upon cat^s. His deductions 
in reference to the cortical and retinal distribution of the 
optic fibers seem to coincide with the physiological deduc- 
tions of Munk. Both Ganser and Gudden seem to agree that 
no connection can be proven to exist between the inferior 
[ corpora quadrigemina or the internal corpora geniculata and 
the optic apparatus. 




THE CRAmJtL KBRVE- 



Flechsig has lately published the results of reiseaftb 
made by him in reference to the optic libera by the de 
tive method. He excludes (as do Gudden and Gansen ft 
cori)as genieulatum internum and the j K>sten or corpus qu 
rigeminum from the optic apparatus. He claims that «ii 
of the optic fibers turn Imckward upon their own conisl 
I'eaeh the radiating fibers of the external geniculate bodyi 
reach the visual area of the cerebml cortex by passing toi 
outer side of the posterior o^jmu of the lateral ventricle, 
places the cortical area of \ision m the cuneu-i and 
ocnpUal lobp, 

A band of fil>ers that crosses in the substance of the ( 
cerebri has been called by Gudden the ''^Irau.'^rerjff pfdnn 
ctilar tfftet^- It extends to the optic lobe of eitbi^ ad^ 
and then disappears. It seems prolmble thai; it in fuortiot' 
ally, as well as anatomically, I'elated to the appaiatoa u( 
%*isioa, because the later investigations of Guddeo IukI 
ti> demonstrate that its fibers have a dii^ect connection «i4 
the risual area of the cortex and the primary c^iitei>» <-* 
%ision. Wilder, in his work on *• Anatomical Technok^,' 
has suggested the term '^cimbta^" for this tract, Mirru^n I 
he does not appear to recognize its association \ 
vmm] mechanism, 

Wernicke has demuu.sti'ated thiit a tract of iil>ers passp* 
from the pulvinar ^a part of the optic thalamus) to tbec^r 
lex of the occipital lobe, and that this tract Ib a din^ 
rontinuation of the fibers of the optic ttact. ft 
the oci^ipital lobe by passing: beneath the ** angular 
Perrler's and Daltons exi)eiiments upon that convoli 
probably affected vision by causing injury to the tr 
Wernicke. 

The MoTouM)cuu and troohleab kxbves have their <W[ 
origin apimrently from a pray nucleus (whicli, acconlini: * 
si>me authors, is common to both nerves) within the irrij 
matter surrounding the aqueduct of Sylvius. This nurii*Q3 b 
in direct cHmimunicattnn with both the corpora qnadrtgemiiBi 
and the lenticular nucleus of the corpus striatum. The on* 



tSm 





OMIQIN OF THIRD AND FOURTH NERVEK 



^37 



^c 



i\ 



pens of the fourth nerve seems to be composed of larger 
^IIs than that of the third nerve, however, and to occupy the 
^vel defined by the line 
}t separation bet'^een the 
anterior and jxjsterior cor- 
pora quadrigemina. 

Some authors deF:rribe 
an additional nucleus for 

the TROCHLEAR NERVE in 

the locus cGpmleus. It 
s appai-ently proven that 
he tibere of the fourth 
lerve decussate with those 
uf its fellow after passing 
backward from its nurle- 
us and piercing the root 

I of the aqueduct of Syl- 
frius. They then traverse 
the cms cerebri and es- 
pape at its superior and 
external border. 
The mwleus qf origin 
(Fig. 45) of the thinl era- 
^pjal n\:tYy^ of each side 
Hpeems to he capable of 
Hjiubdivision into groups of 
Hcells which preside over 
"movement^of sp«?cial mus* 

cles of the orbit, 
H Thuts we may clinical- 
~ly recogni7je the existence 
^of a sfiecial nucleus for 
Brifiua] ** accommodation"; 
for pupillary movements ; 

for the internal rectus, the superior rectus, the levator 
jiebrm, the inferior rectns, the inferior oblique^ and the 
^r ubiique muscles. 



brain, (Wt'niicke.) 

«♦ f.» fiiicliHiM candntti)' ' " ' r,». ,*?♦•«* lenticulA* 
rin; f. rt., iitil*m>r ; f, /^, Ixitty 

of Luy* ; r. r., cxtn U' ; e.ff.f.^^i' 

tcrrml ^cniciilnto body ; c, i.^ cUufttrum ; i., 
Ifilflintl of Ulrl ; p. A, pO!»l«rior eornu ; e. p., 
p»-itiirior ifiiiii / ** I corpora qUBjd- 

rigettiinn uij( , riJiftriiJC fij^iuro; 

trtf optic fitwi- i-» '" 1 ifiji tU k»bo. 




338 



THE CRAyjAL y^EttVES. 



C.q. 



4*^isr. 



\ 



Jn,/V 



v'^^a: 



the oriffih 
Tlie uection i 



This fact probably explains how the existence of ''a- 
terTuU ophthalmoplegia ^ and other distinct forms of ortW | 

paralysis may «^^ i 
from oi^nir l^fikc- 
in the rp^ou iif ik { 
tegTnennjDi. 

The TElGHMOilj 

TTERVK resemhlei ^ 
spinal xierTe« in p»j 
sessing both e 

tor and j- ^^• 

Theanal<'^> ^ ,t^j 
ened, moreortT, 
the deTelopment -^l 
the f^nglion of Gi?- 
ser upon the wemxi 
root The deep Bm 
of tliis nenre deotid 
a detailed dertJy^ 
tion, becanse Hief 
take their origin from several nuclei (shown in Pig, 55), 

1, Some fibers join the trigeminal nuclei of the mcdiilli. 
The sensory nucleus is situated as high as the level nf ike 
point of escape of the nerve from the pons Varolii and it 
analogous, in the opinion of some authors of note, to 
posterior horn of the gray matter of the spinal cord- It eri 
tends along the outer part of the floor of the fourth ventricfc,] 

2, The so-called ^"^ ascending root of the nerre^ is 
ated with the posterior columns of the spinal cord as lawt 
the middle of the cervical region. Its fibers are fonnd to pi» 
through these columns from their origin in the posi^ri^ 
horns to reach the tubercle of Rolando in the nieduUa. Tli# 
fibers of the ascending root of rhe trigeminus aie associaM 
with the sensory portion of that nerve, 

3, The fibers of the so-called ^^d^seendinff root, of (hi 
nerte^^ apparently arise (1) from the cerebellum ; (2) fn^ra tlif 
locus coeruleus ; (3) from a collection of cells in the latenl 



Aj/ /^ autlvor to UluttrnU 
>j the fourth eraniai nfrt*c. 

vrl with the line of dividbn 
between the auteriur and itosteHor quadrigemioal 
bodies. IV. n^ oudeus of the iroclikftr ttcrre; 
4th N., fibcii» of the trochlear oerve; S.^ aque- 
duct of Sjlvluii^; C, (f.y corpora qu&drigemma. 
Kote the decus^AtioD of the fibers in the grej 
mftttcr which aurrounds the aqueduct of Sylvius, 



i 



DEEP ORIGIN OF FACIAL FIBERS. 



wall of the aqueduct of Sylvius ; and (4) from a large-celled 
motor root, in the region of the corpora quadrigemina. The 
descending root of the trigeminus is associated chiefly, if not 
exclusively, with the motor fibers of the nerve. 

The ABDUCENS NERVE arfses from a nucleus within the 
medulla composed of large cells and situated near to the junc- 
tion of the medulla and pons at the bottom of a groove in the 
floor of the fourth ventricle. A communication probably ex- 
ists between this nucleus and that of the motor-oculi nerve of 
fhe opposite side. 

The FACIAL NERVE arises from a nucleus which appears to 
be a continuation of that of the abducens, but lying deeper 
in the substance of the medulla, and also from a nucleus {in- 
ferioT facial nucleus) in the substance of the i)ons. Some 

fibers of the nerve de- 



^maji 



\-"-<j 



scend in the crus cere- 
bri ; probably from the 
lenticular nucleus of 
the corpus striatum of 
the opi)osite cerebral 
hemisphere. The i)e- 
culiar course of the 
facial fibers in the me- 
dulla is shown in Fig. 
65. Gowers denies the 
statement, which was 
once accepted, that the 
facial nerve arises in 
part from the nucleus 
of the abducens nerve. 
The fibers of the facial 
nerve form a distinct 
loop, by doubling upon 
themselves, before es- 
caping from the me- 
dulla. The relation of facial paralysis to lesions of the i)onS' 
has been discussed on page 291. 




aOLf 

Fiflw 76. — SeeHon of the medulla ai tit upper part, 

m, m,/., anterior median flMure; p. m./., posterior 
median fissure; 0, olivary body; «. p.^ sub- 
stantia gelatinota ; /. r., reticular formation ; 
P, anterior pyramid; Va, ascending root of 
fifth nenre; o and a, two bundles of audi- 
tory nerre inolosing r. 6., the rcstiform body ; 
YIII a, ft., VIII fi. n., anterior and posterior nu- 
clei of tlie auditory nerve; n./.t.^ nucleus of 
the funiculus tereles; XII N., nucleus of the 
hypoglossal nerve. 



ZM 



TEE OE AXIAL KBR% Ji> 



The AUDITORY KEBVB aiises from four nuclei wlihrnlk 
8iib«tance of the mednlla. 

A small fasciculiiH eacapes from the meclnlla betweetlb 
facial and auditory nerves, called the ^""partio intermi^i 
WrisbergJ^' This is now considenxi an in no way ivhtfii^ 
the sense of hearing, but rather to that of taafe, Altboogii 
passes, along with the auditory nerve^ into the intemil airiS 
tory canal, it subsequently joins the facial nerve and jir* 
ably helps t^ foiTn the chorda- tympani branch of that nem. 

The nuclei of the auditory nerve lie on a lerel with iki 
broadest part of the fourth ventricle. They are tenn^ 
•* anterior median^'' the ** posterior median/' the "aiilffi* 
lateml," and the "posterior lateral." They have been alueid;^ 
described in connection with the medulla. Some fibeiBol 
auditory nerve have been traced to the superior vermifi 
pn>cess of the cerebellum (page 232). 

Figs. 55 and 7o will show the relative situation of the ft 
acoustic nuclei within the medulla. Some of the fibers of tfe 
auditory ner^e decussate. 

The NINTH or GLosso-pHARYNGEiX jrKKVE arises ts^m% 
nucleus within the substance of the medulla that is not we^ 
mt^ed by a distinc't boundary from that of the pnetimogaistricL 
Its situation and extent are shown in the drawing of 
(Fig. 55). 

The TENTH or PNEiTMoOASTRio KERTEarises &om a nudeof 
within the medulla situated in its lower half in the floor o( 
the fourth ventricle, and also from a nucleus in the vJciiuifj 
of the olivary bmly. The latter is not shown in the d! 
mutic drawings of Erb. The nerve also derives fillers ol 
origin (see page 213) from the trineural bundle (Spttikac 
As the nerve emerges from between the lateral column 
the rtvstiforni body of the medulla, its roots^ betweeii twrf^ 
^^ and fiftt»en in number, lie beneath those of the glosso-pharTB> j 
^^ geal nerve. These roots join to form a flattened fiiseicaliiifl 
W that crosses the ttocculus, in company with the glo€80-p]iat7V*fl 
^H geal nerve to nuich the jugular foramen, " 

^H The ELKVENTU or SPINAL ACCESSORY NERVE 18 f Omed bf 



ptncL 




■H ORIGIN OF ELEVENTH AND TWELFTH NERVES. 341 

li^fcwb divisions, the medullary and the spinal. The former arises 
faom a nucleus that lies within the medulla close to the cen- 
^tzal canal of the cord and is a continuation downward of the 
g^imcleus of the vagus. The spinal filaments spring from a 
- , continuation of that nucleus in the gray substance of the 
cord, as low down as the level of the escape of the sixth or 
.^.seventh pair of cervical nerves. The spinal filaments escape 
' from the lateral column of the cord, between the anterior and 
po6terior nerve roots of the spinal nerves. The medullary 
. portion of the nerve receives accessory fibers from the hypo- 
glossal nucleus, the solitary bundle, and the raphe. 

The TWELFTH or HYPOGLOSSAL NERVE arises from a 
nuclear column (about three quarters of an inch in length) 
! that is composed of large branching multipolar nerve cells. 
Its lower end is situated in front of and close to the cen- 
tral canal, in the region of the level of decussation of the 
pjrramidal tracts. In the fourth ventricle this nucleus forms 
a prominence near the median line, slightly above the cala- 
mus scriptorius. The filaments of the nerve x)ass through 
the inner side of the olivary body, and emerge in the furrow 
between the anterior pyramid and the olivary body. They 
are then collected into two bundles that join with each other 
to form the nerve trunk before they reach the anterior condy- 
loid foramen. 

We are now prepared to consider the sei)arate cranial 
nerves and their branches of distribution. 



THE OLFACTORY NERVE. 

The first cranial nerve, or nerve of smell, consists (1) of 
three roots ; (2) an olfactory process ; (3) a bulb ; and (4) ter- 
minal branches, which are distributed to the cavities of the 
nose. 

The three roots are called the external^ middle^ and i'n- 
ternal.^ 

' The deep origiiif of this neire hare been discossed in preceding pages, as well at 
Ibt probable altiialion of the cortical centers of smell. 



ui 



TBE CRAmAL KBMVMa. 



All three of the roots join to form a band, which m \ 
in form (the olfactory process or tract), which pa 



Turi 



Fig. 76.— ^ooi^ «//Af ct^mOal norm, (HfradiltM.) 

T, First pair; olfactory* 
XL S<K'ond pair; optic. 

III. Third pair; motor oeuli oommuniB. 

IV. Fourth pair; pAtbetieus, 
Y« Fifth pair; nerre of masticatioti *nd iHfBcUl, 

VI. SiTcth pair ; motor ocuU cxtarftus. 

ymII"^"!*?^ ' Seveoth pair. 
VIIL Auditory, \ *^ 

IX, Glosso- pharyngeal, 1 

X. Pneumog:aatric, > Eighth pair. 

XI. Spinal accessory^ \ 

XII. Kinth pair; siibliagual. 

Tb« numben 1 to 16 refer to braiicli«fl which will be deserltietl bMwfl 

ong the floor of the brain in a deep siilcns till it expuL^ 
into the terminal enlargement, known as the '* olfactory \m\hJ\ 
or *' ganglion/' Thia terminal enhirgeraent lies upon li 
upper surface of the cribriform plate of the ethmmd 
tlirough the numerous foramina of which its brujiches escape ■ 
as small, thread*like tilaments; which subsequently f oroi ■ 
plexus upon the surface of the Schneideriui, or pitoltiiff, ■ 
membrane of the nose* 



STRUCTUBE OF OLFACTOMY FILAMEM8. 



343 




Fw. tt.— Ol/actOTjf ^a Hfflu , I Hi rictif eld, ) 

f i^/a^ori/ ffanfffion and nnve* ; 2, branch uf ih rvo; 3^ ^phcno-palaliiie gati> 

glion ; 4, 7« branebe«< of the great palatine dxm i^riur palatine HDrve; d, mid- 

dle piiliitifjt' hcrvti; 8, 0, braocfaea from the s|iii»iio^ji«latbe ganglion; 10, 11, 1:^» 
Vidtan nerve and iu branches; IS, external carotid branch from the Biipcrior cervical 
gaugliun. 

_The filaments of the olfactory nerve are described by 
irs, Todd and Bo\%Tnan ' as differing in their structnra 

the orrlinary filaments found 
the other cranial nerves, in that 
ley ronfain no white substanre of 
?hwaan, and are nucleated and tine- ■ ^ 
gmnular in tjexture* This absence 1 \ 
the white substance, found in 
"other ner^^es, renders it difficult to 
trare their course in the Schneiderian 
membnme; which difficulty is still 
farther enhanced by the existing nu- 
clei, which resemble those of the tis- 
fines thniugh which they pass. 

The limit of distribution of the 



7 



Fro. IS. 'f 

thrift > ■'/ 

oltictory nerves seems to be confined i, fioin tht^ froti— a, epithriui 
U^ the sui>enor thn^e fuurrlis of the 



septum of the nose, the sui)erior tiir- 
biaated b<me, the upper half of the 
middle turl filiated bon«% and the mof 

rbfriologioal AoAtomj/ 



A. olfactorjT crlU. i. Small 
hraniih of the? olfactorjr nerre 
of th^ ftvg, Mpaniting al one 
end into a brunh of rarkoM 
tibrllit. 8. OlfacUir; oeU ol 
thc> thccp. 



344 



THE CRANIAL NERVES, 



of the nasal cavities. These regions seem to be defined by a 
browo-colored tesselated epithelium.* 

Odorous particles, present in the inspired air, as they pass 
thnjugh the lower ohamliers of the nares, are diffused into 
the upper nasal chambers, and, falling iqion the olfactory 
epithelium," jiroduce sensory impulses which are tmnsmitted 
to the l>rain and give rise to the sensutiuns of smell. 

Forced inspiration, or sniffing, increases the upward dif- 
fusion of inspii'ed air, and thus a more complete contact of 
the odorous particles is insured. 

It seems that, for the development of smell, the odorous 
I^articles must be transmitted to the nasal mucous meml>rane 
in a gaseous medium, as the simultaneous contact of fluids 
destroys all appreciation of odor," 

Animals with a very acute sense of smell have a modilied 
arrangement of the turbinated bones, to afford a larger ex- 
panse of surface than exists in man. 

It has been asserted by some physiologists that the olfac-" 
tory nerve is not the only nerve of smell, and Magendie 
claimed that animals could perceive the odor of some sub- 
stances after the olfactory bulbs had been removed. He used 
ammonia, however, as a test in his experiments, which is 
hardly a test of smell, as it is a powerful stimulant to the tif th 
nerve. 

Bernard ' i*eports cases of absence of the olfactory bulbs 
in man, where smell existed dmlng life, Prevost,* how^ever, 
claims that section of the olfactory bulbs entirely desti'oys the 
sense of smell. Injury to the fifth nerve may also destroy 
smelly even where the olfactory ner\'e remains intact ; but this 
effect is hardly a proof that the nerve is in any way related to 
that special sense, since the effet*t is proltably due to an altered 
condition of the nasal mnvons memhrane^ which i>revents it^ 
performing its natural function. The loss of smell may, 
therefore, be of some diagnostic value, if assr^ciated with other 
symptoms referable to impairment of the fifth cranial nerve. 



1 Max Schttltse. 



* Mich. Foster, " Toxt^Book of Physiology." 

* " ArchiTOB de ed. phys. et rnit," 1871, 



THE PERCEPTIONS OF ODOR. 



845 



It seems necessary, in all animals which live in (lie air, 
that all iwlonius niaterials must enter the nostril to lie jier- 
ceived, and, fiirthenriore, that the membmne of the nose nmst 
' be in a proper condition of moisture ; henee, by breathing 
through the month, the most disagreeable of odors may usn- 
ally be unperceived, and the blunted sensibility of tlie power 
of .smell, which occnrs in catanii, may jiluusibly be exj)lained 
as the result of a deticient secretion in the early stage of the 
attack, and of excessive secretion later on in the disease. 
The cnrious effects of section or injiiry of the liftli cranial 
nen^e upon the sense of smell may justly be attributed %<\ the 
alteration in the amount of secretion of the lining mcmluiine 
of the nose, since this nerve exerts a marked intluent*^ u]K>n 
the secretions of the tissues supplied by it. 




KlO. 79. — IntovmJ hratirhcit of the of/€tetor>i Vfter Sappcy*) 

1, internal bi nnt'lit'M of the olfnctory bulb, raruifvb^p in the mut'oue mcmhraDC eoTt'rinj» 
the w?ptum «if tUt^ nfljittl fosfa? ^ 2, internal braneh of the etbmoitlal dkision of the 
nnsal nerve ; 3^ iiAt"f>-pflilatini" nerves ; 4^ t\, 6^ caveniou? plexnH ; 7, superior or 
aficending Itranches of this ph-xue ; 8, int«^mal carorid branch from thp stipeHor tw* 
vical ^aticrlkm; % ^, filaments eonnectlntt thi;* branch with the external carotid 
timncb ; 10^ orip^n of tbiB branrh ; 11» panplion of the fj^loH*i>phar7iij;enl ; 12^ J^ig^i- 
I 'in of tbe pneumos:ni4tn€; 1*?, anai^tomoric tilamt'ur^ extentiing from the 

1. to the two preeedinp tiervcfl ; 14. mm^tonjosL-i of the ppintil nect?>'!iory 
w.... ,.., [inieuinogastrie ; ir», OlnTm^cit cMmnccting: the sympiithotie with the hypo- 
glossal; I, olfactori- ; II, fiptk ; HI, motur oenli ; IV^ pfttbeticus ; V^ trigt'«iiim» ; 
VI, tbduceii**; VII, facial; VIII, nuiliton; IX, glo9j*o-phnrTTigeal ; X, pnciimog«». 
trie; XI, spinal aceoj'nory ; Xll^ bypo-glo^sjib 

Tlie act of sneezinf/, by whicli a foreible blast of air is 
driven thrcmgh the nostrils, is c»ften mi effort on the part of 
Natnre to get rid of some irritating substance ; and thus. 



TBS CBAyiAL XBMVES 



through the agenoy of the fifth nerve, is the nose Dudej 
portal qf the Tt^iratory apparatus^ where eognkaocct 
quality of the air breathed is constantly taken, and wh 
foreign or injurious matters are at once detecredr wsd < 
expelled. 

A marked peculiarity of the olfactory nerve ii> hHuhJ 
the fact that no form of irritation of its fibers exdUsi 
muscular action through other nerves ; ' neither is ii ctfiikl 
of the sensation of pain, since section of the nerve, or fraib| 
destruction of the olfactory ganglia, seems to create iind(iai| 
distress in animals, and the nose retains its normal 
ness until the fifth nerve is also divided. 

The olfactory nerve, however, may be the 8oqi«« of 4 
variety of marked reflex action. Manj" cases are rrrcfWl 
where /a eW my and wviitlng have been produced by<»i«| 
odors; while, for some unexplained reason^ mental 
tions cluster around sensations of smell more stronilT \ 
any other form of impression received from without* 

The importance of the sense of smell among rkuij -^ 
lower animals, in guiding them to their food, or b 
them warning of danger, and also in excitiog the liexual I 
lags, is well known. Among the savage tribes, whrise 
are moi*e cultivated than those of civilized nations, the 
is almost as acute as in the lower mammalia^ It is aasf*rti!<l t? 
Humboldt that the Peruvian Indians, in the middle irf it 
nighty can thus distinguish the different races, whether 
pean, American, Indian, or Negro. 

The agreeable or disagreeable character assi^ed tx> 
particular odor is by no means constant amon^ diffenmt in* 
viduals. Many of the lower animals pass their whtile 
in the midst of odors which are to man (in a civilized ecu 
tion) in the highest degree revolting, and will even refit« 
touch food until it is far advanced in putridity.' 

' Ckirpenter, *' PrindplM of PhyBiologj.'* Th< ftct of wmMh^ mmj poiriMf 1 
sidered m an exception to this statemeot, 

* Micli. Fo«tcr, '*Teit-Book of Phjwiology/' ISSO; TodJ ftiuf Bowmaa. 
Atmtomy/' 

• Carpenter, ** Prindplci* of Humui Pbj^ology/* 



it 

if 

t 
r 



"B5 ABNORMALITIES OF THE OLFACTORY SENSE. 847 

■iiii It is difficult to say when effluvia have been completely 
^i^iemoved from the nasal passages, since it is not unlikely that 
^lOdoTous particles' (supposing such to exist) are often ab- 
i^jBorbed, or possibly dissolved by the mucous secretion. It 
frequently happens, in regard to odors and savors, that habit 
^^makes that agreeable, and even strongly relished, which was 
^^ at first avoided ; the taste of an epicure for game that has 
.^ acquired thefumet^ for assafcBtida, garlic, etc., is an instance 
. of this. A case is reported, where, in a state of hypnotism, a 
youth had his sense of smeU so remarkably heightened as to 
be able to assign, without the least hesitation, a glove placed 
in his hand to its right owner, in the midst of about thirty 
persons, the boy himself being blindfolded ; ' and modified 
forms of this excessive development of this power of smeU 
az6 by no means rare. 

The word " taste '' is often used when the word " smeU " 
ahonld be employed. We speak of tasting odoriferous sub- 
stances, such as onions, wines, etc., when in reality we only 
smell them as we hold them in the mouth. This is proved by 
the &ct that the so-called taste of these things is lost when 
the nose is held or the nasal membrane rendered inert by a 
catarrh.' 

CLINICAL POINTS AFFORDED BY THE OLFACTOBY NEBVE. 

The nerves of smeU may become the seat of disease, or may 
simply manifest the presence of disease in other parts. The 
two conditions, which are clinically recognized as indicative of 
existing disease, are hypersesthesia and ansesthesia — not of 
the sensibility of the part, in its generally accepted sense, but 
an increase or decrease of the acuteness of the olfactory sense.' 

' GAipenter, op. cU, 

^ FoUer, op. cU, 

* Aooording to Althaiu, if the mucous membrtne of the nose be irritated with very 
•trong galfanic currentfl, the taate of p^totphorui is produced ; but no i>crception of odors 
li peroL>i?ed, altlioagfa pain, fcrtigo, and senMitions of light may be created. It is cus- 
tomaiy, therefore, to use other means for the purpostc of testing the acuteness of this 
•fiecUl ■enae, and the moat sucoeasfui method consiMts of uial&ing the patient smell differ- 
ent odori, Ofling the noatrils alternately, and avoiding all things, as tests, which would create 
an irritation of the filamenta of the fifth nerve, such as ammonia, acetic acid, snuff, etc. 
(Heneo the defect in llagendie*s experiments mentioned on page 344.) It is advisable 



TEE CRA.VIAL 



To the former cjondition, the term ^"^ hf/perasmia^* fai 
while the latter is called 'Uinosmia.^^ 

The condition of lij^erosmia Ls often i>eroeh'ed, JiSftU^' 
pomry excitation, in patients recovering fix»m some i>futi8 
diseaae which ha8 exhausted their nervous |Kiwer, andii 
in the hysterical and insane/ Should the preaenoe ol« 
natural odors, or a marked increase of the sose^tibiliJTt 
udors, exist in the insane, it may indicate the exi5iii!«i^< 
some type of neoplasm involving the frontal lobes at tfaetit 
of the cerebrum, localized flisease (softening, as a ni^ 
olfactory bulbs, or adhesion of the olfactory bulbs tu uic - 
mater ; since all of these conditions have been found at 
siea, where such symptoms existed during life, "ihs^ 
reports a curious case, where such a Babjeet was Ifcibk* i 
epileptic attacks, and where the attacks were a^sociati^ 
abnoimal sensations of taste ; the autopsy showed a 
of the left olfactory bulb. 

The abolition of the sense of smell is a sympt<im of 
fn»quency, as well as importance, than the excitation irf 
special sense. In rare cases, as in one i't?i)orted by Ll 
the absence of the power of smell may be a congeniuil d< 
Anosmia may be develoi>ed, as a temporary conditiaii^ duiiif 
an attack of acute catarrhal inflammation of the nitres, wtei 
alters the character of the membrane, or, in chronic catmik 
by the effect upon the natural moisture of the mucous 
of the nose. It may be present in " Bellas ijaralynis,''' 
the facial nen e no Icmirer affoixls motor power to the mu! 
which (Ulate the nostril, and thus the entrance of air to 
upper nasal chamber is obstructed. Anosmia may be oiwj d 



laM. 
otJI 




Id itfii <Mkw« whidi ^ft both •grse^ble and di«a^;Ti?e«bIfl ; heoee ootogn*, €«aipiboc 
•tCL, 4m the" (Hic kiAml^ and TAlerimn^ i^^ftaffpMda, turpentine. 0ulphuret«d liji|jcn|ww 
ibe Olber ItAtiil^ Arm ctinimcial? Finplojed. It is aUo ouotntnanr Ut jiliioe 
•ueb M e€>tfi^\ mine, [him*r\ snd cheese, v^ifhin ihr mmtih^ m% Ihmt ibo 
tbs nose am jH^nvlvir tbifro, Htn«» the odoKferoai partidcs p«*«« v(»«rmx4 hj 
libftTfux, r«tb<»r %^ ftu fma^nsrj tojtte, bowerer, than aj triM^ olfiMlqr^ 

* F>««v)''"*^l^ fHlotM of the mm% pleaaant character, fuob ■« tboM of flbwvni, 
Q«nsl(n faifitifij;, nauMi^a, headache, or eren cofirulsiofii^* ^n tb{a almm of 
odors naiiAe^iintir to olben niaj be tolerated, aiid, |)OS9ibtj^ pncferred bj 

* For ttf« aTvuptoma of tbia aHedJoo, tm ptgM of tliU Tolaine deicripOv^ of lbs 




1, THE NERVE OF VISION. 349 

jpthe manifesta^tions of tumor at the base of the brain ; of ab- 

aoess of the pituitary body (as rei)orted by Oppert) ; of syphi- 

B-Utic thickening of the i)eriosteum and mucous lining of the 

j^noee; of lesions resulting in paralysis of the fifth cranial 

-J, nenre, for some unexplained reason ; of hysteria ; and, finally, 

jjj, of certain types of insanity. A partial loss of smell has been 

I,, known to follow typhoid fever and meningitis, in which case 

the sense is usually regained. Chronic rheumatism, chronic 

^ tliiiiitis, and traumatism, have also proven exciting causes of 

a temx)orary but serious loss of the sense of smell.' 



THE OPTIC NERVE. 

The second cranial or optic nerve presents for examination 
from before backward : 1, the optic nerve proi)er ; 2, the op- 
tic conmiissure ; and 3, the optic tract. 

The optic tracts of either side extend from their point of 
apparent origin in the anterior corpora quadrigemina^ where 
tbey receive fibers from the optic thalamus and the external 
geniculate bodies,' to the optic commissure, to reach which 
point, each is compelled to pass around the eras cerebri. In 
their passage around the crus, each tract receives a few fibers 
of attachment at its anterior margin ; and, after leaving the 
crus, just before the optic chiasm is formed, each receives 
additional fibers from the lamina cinerea and the tuber 
einereum 

The optic commissure or chiasm is formed by the junc- 
tion of the two optic tracts, and from it the two optic nerves 
diverge to pass to their distribution in the retina of either 
eye. The construction of the optic chiasm is of interest both 
from an anatomical and a physiological standpoint. In it, 
four sets of fibers may be demonstrated, called, respectively, 

' In almost all caaes, where anosmia affoctii both sides of the nasal cavity, the sense 
of taate It alto impaired. Ail aromatic forms of food and wines have a distorted flavor. 
It it daimed bj Ogle that the pigment in the olfactory mucous membrane has some effect 
apoa the tente of tmelL 

' Phytiologioal exporiment teems to point to the occipital cortex as intimately con- 
B0eC«d with the deep fibcrt of the optic nerve, as mentioned in the preceding section. 



mT 



TSB OBANIAL KEBVES, 



^17 



I /I 



Fi^. 



%ti f 



tlie inteT'Cerehml fibers, which are situated at the p^i-l 
rior portion of the commissiUB, and coanect the two hdi 

spheres of the cerebram ; line • | 
ter'T€Hn4il fibers {i)^ which arpii 
ated in the anterior portion tih\ 
chiasm, and connect the retiai<t| 
one eye with that of tli 
langiUidinal fiders^ vv 
the external side of each o( tk\ 
optic tracts, and cod' 
ina with the c^^n^biiiJ 
of the stime side ; ;: 
the deeussatinff fibent^ i 
thjuugh the center of 
chiasm, and 8er\*e to 
retina of ea<?h eye mi., 
site cei^bral hemisphere. 

Tlie optic nerve pn^iier 
from the anterior part lif the 
coiumissure and enters (T-^* -'^^- 
foraraen, in company with 
thalmic artery^ being finntvfin 
by a tubular process of Axmi ; 
which, as the nerve enters 
bit, subdivides and fortn* Ixiti 
sheath of the nerve and the 
OS ten m of the orbit. The ma^ 
pierces the sclemtic and choroid coats of the eye, about mt 
tenth of an inch to the inner side of the lixis of the ey<v a»i 
then divides into numerous small fibrils, w^hich appmr '*• 
spread themselves out fr<)m the papilla of the letiiia mm^ 
what like the spokes of a wheel. 

In the accompanying diagram,* which \b not giTen as na 
accurate representation of the parts, but rather a^ an ai 
memory, and to render plain what words alone micrbt ro^^^ 
obscure, the fibers of the optic nerve are seen to enter thi- ^ 

• After Wetter, of 



1, infimdibuliim ; 2, w>'pm tinnt- 
tim / Jt^ cnrp'irii albicintii ; 
4, rtrrftr^i^ ftriinne^fi ; 5, tuber 
niinularc ; rt, opfit tree's and 
nrrvci^ <hrvu3at*nif at tfu com* 
missure^ or chia/im ; 7^ motnr 
oeuli eijmiiitmb; B^ (mtheticiLf; 
Di tilth nerre ; U\ motor ricttli 
fxteinits : 11, fneial norre; It, 
aulitorr ncrvo ; 1^, nerve of 
Wriiib<*rg ; 11, glo^^cKpharyri- 
gieal nenr .* ; 1 5, pncumogasiric ; 
lA, spinal iiccessoi^; 17, sub- 
ItogUAl n'rrc. 




DISTRIBUTION OF OPTIC FIBERS. 



851 



at the point designated by the letter P, which is called 

le papilla, since, at this point, the retina is slightly mised 

^uva the i^maining portion. This papilla is not in the exact 

Iter of the retina, since tliat point is reserved for the macula 

ecu, in the center of the so-called '' yellow spot of Sommer- 

where the most exact vision of extenial objects is ob- 




HL — Digram 0f the dtcuMftthn at 
tgAt opiU eomin iifuiv. { X fl i>r ¥\ i at . ) 

dotted lLQi<0 #ibofr the four dinn?- 
tloDJ of the libcr&. 



Fto. fttj. — A diagram in show the cottrfit of 
the ojdic/ibtri in the retina. (After Wubcr.) 

p, the papilfa, where th«? optic nerve enter > 

n^ the macula hUi^. 



ined ; but it is placed to the inner side of the center, and 
irly on the name level wirh the yellow spot. It will be seen 
It those nerve Hl)ers which are distributed aronnd the ydlmo 
of Somnierlng are directed outward in a nearly stmight 
le frr»ni the pajnlla, as are also those which supply the part 
itemal to the papilla ; Imt that, in order to avoid crossing 
ae yellow spot, the fibers are compelled to \ms^ in a nior** 
less curved direction to the other parts of the retina, 
rhereas, If the papilla were in the exact center, the fibers 
%f the *)ptlr nerv^e would probably have l^een stniighf, and 
aiTungtMl as the radii of a circle. Tins arrangement of thp 
optic fibers differs from that described by some of the text 
books on physiology^ ime of which, to my knowledge, states 
bat they ar^ aminged aa a plexns, and tliat the frequent 
1cm gives a i>ecnliar "net-like'^ api)6anmce to the 



ii^ 




352 



THE CRANIAL NERVES. 



optic fibers.' Probably the fact that the nerve fibers loaej 
their sheaths as soon as they enter the retina^ and thus, 
unless they l>e previously stained, afford some difficulty in 
tracing them, explains the eiTor in description. 

REFLEX ACTS EXCrTED BY THE OPTIC NERVB. 

The optic nerve differs fiT^m the olfacttiry nerve in one im- 
portant resf>ect, viz., in its power of conveying impressions 
which create reflex muscular movements.' The motions of the 
iris are always influenced by the amount of light which enters 
the eye, and which thus affects the optic nerve filaments. 
When the optic nerve is divided, the pupil imrnediately con- 
tracts, unless the third cranial ner^'e, W'hich controls its move* 
ments, is also severed, when the iris fails to be so affectM/ 
In rare causes of disease, wdiere the sight of one eye has been 
destroyed by some lesion of the rjptic nenre, the pupil of the 
affected eye will be found to move in unison with the unin- 
jured eye ; but this effect is to be attributed to a motor impulse 
created by the influence of light upon the retina of the normal 
organ. In some cases also, w^here the tissue of the cerebral 
hemispheres has undergone changes whicli render the percep* 
tion of objects impossible, the pupil may still be seen to re- 
spond to the variations of the quantity of light which enters 
the chamber of the eye ; thus showing that the optic Jierm 
alone is required to create the reflex act upon the pupil 
through the third nerve, irrespective of the brain. 

In addition to the power of the optic nerve to cause 
changes in the pupil, there is still nnotlier fonn of reflex act 
which deseiTes notice, viz., its power of producing rontra<*ti*>n 
of the orbicularis palpebrarum ihuscle. This is pe received 
w^hen an excessive quantity of light renders the effect ui>on 



' Carpenter, op. ci£. 

* Carpeater^ op, cU, (It is a question \t fainting and vomiting can not b«? otUiii justly 
regarded as reflex musculnr acts, dependent upon the seni^ations perceived through the 
u! factory nerve,) 

• Doubtle.^5 on account of the fiimultaneoua diyisbn of syropathetic nerrc fibers^ which 
arc probtibly deriv<xl from the fifth x^rre ; th«fle accompany the optic nerre and Uiuscon- 
tml the diluting fibci-s oi the iris. 



DECUSSATION OF OPTIC FIBERS. 353 

. the retina one of pain, or when objects to be perceived are 

brought into too close proximity to the eye. Thus, in photo- 

'phobia, the peculiar half-closed condition of the eye is not 

purely a voluntary act, as the eye is, at the same time, rolled 

^"' upward and inward to a much greater extent than can be per- 

fonned in response to a merely voluntary effort. 
' The act of sneezing may often be excited by the visual 
r; sense, when a sudden exposure of the eyes to a strong light 
% occurs. That this reflex phenomenon is due to the excitation 
y of the optic, and not to the olfactory nerve, is proven by the 
; fact that, unless the light he seen, the attack of sneezing does 
; not take place. 

DECUSSATION OF THE OPTIC FIBERS. 

The object of the decussation of the fibers of the optic 
nerve has been explained by WoUaston,* Mayo,' and others, 
as an arrangement on the part of Nature to have the fibers, 
which spring from each optic ganglion, distributed to the cor- 
responding side of each retina ; the rigid optic ganglion be- 
ing thus associated with the outer portion of the retina of the 
right eye and the inner portion of the left eye^ while the left 
ganglion is distributed to the outer portion of the left eye 
and the inner portion of the right eye. If this be demon- 
strated as true, each optic ganglion must perceive objects on 
the side opposite to it ; since the images of things seen by the 
retina must fall upon the outer side of the left eye, when 
placed upon the right side of the eye, and vice versa." 

A similar decussation of ner\'e fibers is known to exist in 
both the posterior horns of the spimil cord and also in the 
anterior i)yramidH of the medulla oblongata ; and the same 
arrangement in the optic nen^es, which are known to be of 
the greatest value in preser\'ing a harmony of motion through- 
out the body, may be for the object of bringing the visual im- 
pressions into a more direct and proper accord with the motor 

1 " PhilcM. Trans.,** 1824. 

* Soe Carpenter*! '* PhjHiolo^.** 

' See beAring of this arrangement on diagnotfis of cranial tumors, later on in this 



8M THE CRANIAL NBBVBSL 

apparatus. In support of this view, it is found that in i 
invertebrate animals, where the optic fibers do not den 
sate, no decussation of fibers exists in the general mfl 
system. 

In some animals, where the two eyes have an entiivlyd 
f erent field of vision, the decussation of the fibers from ea 
optic ganglion is found to be complete," the longimdiml^ 
being absent, and the whole of the fibers from each gangB 




OPTIC MCRVC . 



.OPHTHAU4IO 

ARTCinr. 




Fig. SS,^JUiation of nerve and arUrif m the cpHe/aramm. 

I 



MCMVC. 



l.2.3.4.5.ClllAKr ARIXRICS. 
Fig. 84. — Rehtiong of optic neitfc to tends in the m-bit 

passing into the opposite eye. This arrangement can be i 
ceived in almost all of the bird species " and in some of 

osseous fishes. 

RELATIONS OF OPTIC NERVE IN THE ORBFr. 

The relations of the optic nen^e to blood-vessels mav b 
often a bearing upon vision. It passes throngh the op 

' Tho decussation of the fib?rs of the optic nerve seems also to be influcocvd lin 
by tho extent of the field of vision which can be covered bif both rvr» simaluneov 
The bundle of decussatinj!^ fibers differs, in its relative size, from the bundle of ooc 
cussating fibers, in diflferent animals, who possess a stereoscopic porception of oh^ 
(their vision being binocular): and the extent of the field of binocular vision seem 
explain this fact. It is said that certain birds (as the hawlc, for example) have an »: 
tional power of vision afforded them by means of two maculs luteop in each ratiiu; 
that, having two spots of distinct vision in each eye, the eye can the more r««dilv foi 
suddenly upon any object 

« Solly, ** The Human Brain " (Am. edition). 



r. RESULTS OF DEFECTIVE VISIOK 365 

Lj; foramen in company with the ophthalmic artery, and is siir- 
y^ Tonnded, for the balance of its length, by the ciliary arteries, 
^; which lie in close relation with it. It is also pierced by the 
arteria centralis retinoid which is thus enabled to reach the 
. papilla of the retina, and, from that point, to ramify through- 
out that membrane. 

It can be readily understood, therefore, how any vascular 
,' growth within the orbit would be liable to press upon the 
fibers of the optic nerve, or to create sympathetic changes in 
the vessels of the retina itself ; while, as an anatomical fact, 
the enormous collateral circulation which exists on account 
of the frequent anastomosis in this region, renders such vas- 
cular growths within the orbit by no means uncommon. 

ANATOMICAL DEFECTS OF VISION AND THEIR CONSEQUENCES. 

A ray of light falling upon the retina strikes the expansion 
of the fibers of the optic nerve, and creates what may be called 
a sensation of light. What this sensation is, it is not within 
the province of this work to discuss, nor is it possible, from 
our present enlightenment, to explain how the brain trans- 
forms impressions, received from the fibers of the different 
nerves of special sense, into an actual recognition of either 
smell, sight, taste, or hearing. This should not deter us, how- 
ever, from carefully studying all the mechanical ingenuity 
which Nature has shown in the arrangement of certain parts, 
or from attempting to interpret her aims and purposes when 
any such subject of inquiry seems to be presente<l. 

There are certain practical points i)ertaining to the mechan- 
ism of visicm concerning which every physician should be in- 
telligent ; since a recognition of existing optical defects and 
their bearings upon health will often enable the medical a<l- 
viser to guide aright those consulting him, when other\^'ise 
serious consequences might follow the very lack of this i)r.K'- 
tical knowledge. 

The most common optical defects * are, undoubtedly, 7///- 
peropUiy or far-sightedness; myopia^ or near-sightedness; 

> Bowman and Todd, *' rhj^iological Anatomy." 



356 



TEE CRANIAL NERVES, 



and aHigiiiatism^ causing imperfect perception of objects in 
certain meridians of vision. 



FiGv 85. — Diagram tfi Uhtstraie congenitat or acquired drfed* in the antero-potterior diam^ 
0ter of the et/e. The blaek line rt-preseots tho n^mtal line of the eye. No, 1 repre- 
sents the h/peropic eye ; 2, the mtfopie eye ; 3, the optic nerve. 

The first of these condilions indicates, as a rule, a cnngeni- 
tal or acquired drmhiution m the antero-posti^ior mtls of the 
eye. Thus, as age advances, the eye either naturally be- 
comes flattened, or the ability to accommodate for distance be- 
comes impaired, and visicm necessarily Ijecomes presbyopic ; 
but, in many cases, children are bom with this defomnty, 
which often goes too long unrecognized. Were Nature not 
able to compensate for this abnomiality by means of the cili- 
ary muscle, which, by altering the shape 'of the crystalline 
lens of the eye, is enabled to increase its convexity, and thus 
artificially to focus near objects, such cases would lie imme- 
diately made known by the inability of the patient to read 
or even to see near objects with distinctness. But such causes 
go on fi'om year to year, struggling, \^ith the aid of this mus- 
cle, to see, and thus wearing out their vital energy ; trying 
to excel in their studies, only to fail from the fatigue wWch 
attempts at study bring about, which they themselves or their 
parents can not explain, and which often causes them to in- 
cur bodily chastisement ; and seeking, as a relief, ont-of-door 
amusements, in wliich they usually excel, since little muscu- 
lar effort is required to perceive objects at a distance. 

* Foster, Volckcrs, Hensen^ and Hock claitD that the increasicd eonvexltj of the lens 
i» due to the reUxfttion of the auspensorj ligament, thus allowing the lens to bulge for- 
ward from its own elasticity. 



RESULTS OF DEFECTIVE VISION. 357 

How cruel and injurious to health must be compulsory 
education to such a one, till, by the aid of property adjusted 
glasses, reading becomes a pleasure ; study no longer a bur- 
den, but a joy ; and nervous headache, throbbing in the orbit, 
double vision, and other e\idences of nervous prostration, are 
numbered as among the things of the past I ' 

On the other hand, myopic patients can not see objects at 
a distance, since their eyes are too convex ; but only when 
placed close to the eyes are the beauties of outline fully per- 
ceived, and distinct vision rendered possible. Out-of-door 
exercise is, to children of this type, a burden and a disap- 
pointment, since they can not enjoy Nature in her most beau- 
tiful aspects, nor indulge in sports without danger, which to 
the healthy child, with perfect vision, is harmless. Such 
children seek enjoyment in books, the contents of which can 
be seen by them and easily read ; the flields are discarded for 
the parlor ; the enforced retirement is wrongly construed by 
the i)arents and physician as an indication of precocity and a 
taste above that of the romping child ; the health is imper- 
iled, the intellect weakening by undue strain, and the mind 
made one of ideals rather than of realities, since pictures and 
book representations are to them Nature in her true aspects.* 

Astigm^itisvi is a condition due to the fact that either the 
surfaces of the cornea or of the crystalline lens are not of the 
same curvature^ but are more convex in some portions than 
in others, or in the i)erpendicular meridian than in the hori- 
zontal. This abnormality of contour causes a distortion of 
the image of objects in the field of vision. If black lines, of 
equal width, be drawn parallel with each other, and several 
placed perpendicularly on one portion of a i)age and several 
horizontally cm another portion of the same page, such an eye 
will see one or the other set either less distinctly as to outline, 
or one set will appear darker than the other. 

Almost all eyes are slightly astigmatic^ and generally with 
the greatest convexity in the vertical meridian. And the same 
irregularity in lenses can be demonstrated by attempting to 

' Bee article by Dr. Loring, "^ Harpcr> Mig.,** August, 1879. 



358 



THE CRANIAL KERV 



focus light from a liiminons point, when the image 
found to be radiated, instead of a perfect cirele, astti 
be fi^om a perfect lens. 

In choosing spectacles, for the purpose of correcting •Wf] 
of the eye, it is of great conseqaence not to make jum^l 
compensation; for this has a tendency to incrMaae theMesi 
besides occasioning gi^at fatigue in the employment 4 A | 
sight. 

Prom observations previously made as to the mechajte] 
of the action of the ciliary muscle upon the lewnk ' 
vision is accommodated for near objects in case tl. 
normal, it may be understood why all power of acn » 
tion of vision is lost after the operation for cataracL 

A TEST FOB MYOPIA klSTD HYPEROPIA. 

B F P T Z Dl 
D I. T Z F P E 

P F Z T L 

The normal eye should read letters of this kind and ia 
at twenty feet. Vision is then said to be normal. 1* 
can not do this at twenty, but can at ten feet, then vi?iiMn i* 
ten twentieths, or one half of the normal, and so on, 4 

To test the eyes, place the letters at twenty tt^i dill 
tance, in a good light. Try first one eye, and tlien lli^ 
other. 

Any eye which can not read the letters fluently* at this i 
tance deviates from the normal standard, and shoald ham { 
thorough examination. 

To test for the defect which has l»een uienTiunecl in 
foregoing remarks as astiinnatism, place thedmuin^ ^ 



TESTS FOR DEFECTIVE VIST OK 



'6M 



tg parallel lines arranged vertically and horizontally, at lif- 
or twenty feet, and be sure to test each eye separately* 



A TEST FOR ASTIGMATISM. 



liese lines should appear eq!ially distinrt ; that is, those 
running %^ertieally should look a.s black and clearly defined as 
those which run horizontally, and vice versa. It however, 

Piere is any difference between them as to shade of color or 
istinctness of outline, the eye is astipnatic, and the greater 
le difforencv, the greater the degree. Such an eye as this 
n^qulres peculiar glasses, which can only be determined by a 

fc^eful examination, and which have to be selected to fit each 
g^ It may be that a person is not astigmatic for vertical or 
llzontal lines, biit is for those running obliquely. To test 
this, turn the drawing so that what ai*e onlinarily the vertical 
ltii6$i shall run obliquely, say, at an angle of forty-five da- 
ps. 
If, now. this were all. It would be a simple matter for the 



ii^ 




360 



TEE CBANIAL NERVES, 



parent or teacher to determine just what childi*en needed a 

cai'eful examination, but, onfortunately, there are a large 
number oi rhililren who, as has J>een already ex]>lained, have 
a deticiency of optical i>ower, but who can, nevertheless, neu- 
tralize this deficiency by an effort, so that they can see at as , 
great a distance and as cleai'ly as those who have normal eyes. 
These are those who most suffer from headache, and from all 
the ills of a nerv^ous natnre which have been detaUed in the 
foregoing remarks. The only satisfactory way out of the dif- 
ficulty would apjiear to be, that every child should have the 
optical condition of the eye and the amount of vision deter- 
mined, l>efore school life begins, by some competent pei^son 
tmined in the methods of making these examinations. 



CHANGES IN THE PUPIL. 

The pupil of the ej^e may be seen to dilate when distant 
objects are to be i^erceived, and to contract when near objects 
are inspected, since, by so doing, the amotmt of light which 
enters the eye is regulated, and the distinctness of the image 
is thus increased. 

Initation of the optic nerve, by an exce^ssive quantity of 
light, also creates contraction of the pupil ; while the same 
condition may be the result of simply turning the eyeball 
inward/ 

In the early stages of anaesthesia* from chloroform, in 
alcoholic excitement, in poisoning from morphia, physostig- 
min, and some other drugs, and, finally, in deep slumber^ the 
pupils are found to be contravted. 

Dilataiion of the pupil may be dependent upon a dim 
light, an att^erapt to view distant objects, emotional excite- 
ment, the latter stages of anaesthesia from cldorofonn, an<l 
fi^om belladonna poisoniug and that of drugs of similar 
action ; while it may also occur in all conditions creating an 

^ r iDiij iK^re saj tbat ^* flm&ll and imeqiml pupils in a person of middle af^e, from 
twenty-five to sixty, should lead to iia inquirj into the poB^iblc cJtwtcace of one of thre<? 
morbid state-s, vii, : pRralytic dementia (or general paralysis), sclerosis of the posterior col- 
umns, and cardiac or aortic disease (iatni'thoracic diacAse)," (E. C, Seguln.) 

" Mich. Foster, '* Tcii-Book of Phyaology," 



? VISUAL SENSATIONS. 861 

t excess of aqueous humor within the eye, and during dyspnoea 
^ and excessive muscular exertion. 

The mechanism of the action of the pupil will be more 
? properly considered under the description of the third nerve, 
• ipvhich furnishes it with motor i)ower. 

VISUAL SENSATIONS AND THBIB MODIFICATIONS. 

Shadows thrown uj)on the retina are perceived as specks in 
the vision, the so-called musc(Z volitantes^ They may arise 
from tears upon the cornea, a temporary unevenness of the 
cornea after the eyelid has been pressing upon it, imperfec- 
tions of the lens or its capsule, and from shadows produced 
by the margin of the iris, esi)ecially if it be imperfect. 

They are distinguished chiefly by their almost continual 
change in i)osition, when the head is moved up and down, 
and by a tendency to entire disapi)earance when an eflfort is 
made to fix the vision upon them. 

That i)oint on the retina, the papilla^ where the optic nerve 
pierces it, is called the "blind si)ot,'' since no sensations of 
light can be perceived in that locality.* 

In that i)ortion of the retina, the "macula lutea," where 
the images to be perceived by the optic nerve faU most direct- 
ly, and where most of our visual perceptions are therefore 
gained, a markedly yellow pigment exists, which tends to 
absorb some of the greenish-blue rays of light ; hence what 
we perceive as white in color is, in reality, more or less yellow. 

When pressure is forcibly exerted upon the eyeball, the 
whole retina speedily becomes insensible to light. This fact 
haa been explained as the result of a loss of the conductive 
power of the nerve structures. Exner," however, endeavors to 
use this fact as. the basis of an argument to prove that the 
sensation of light is the result of some substance (as yet un- 
determined) within the retina, whose production is tempora- 
rUy arrested by any pressure upon the ej'^e which is suffi- 
ciently forcible to occlude the vessels of the retina, and thus 
to interfere with its nutrition. 

« BownMui, •« Pbyi. Anal*' • Uelmholtz, " Phys. Optik.'* « Op. ciL 



862 THE € RACIAL NERVES. 

THE PKKCEPTION^ OF COLOR. 

The subject of color blindness^ which is to-day assuming 

great iinp<jrtance, natumlly suggests to the inquiring mind — 
by what anatomical armngement are the optic nerve hbers 



^^ 



•/A 



m 



mM^^ 



Fio. 8ft. — Crjf9falHne Ims, mttenor view. (BabuchiiL) 

informed, through the aid of the coats of the retina, of the 
perception i)y that membrane of the color of images ? 

That the retinjB of animals possessed color was first noticed 
by Krohn, as early as 1839 ; but the matter was not regarded as 
of any physiologi(?al importance until Boll, in 1876, announced 
that the retina of all vertebra ted animals possessed a puri>lish 
cnhjr, whi*"h faded in the light, but which darkness restored. 
He concluded that the color must be largely concerned in the 
act of vision.' 

The subsequent experiments of Kiihne upon tliis subject 
seem to have partially verified this discovery, but exactly what 

* A very interesting article, by my friend Dr. Ayres^ of this city, appeared in the ** New 
York Mod. Jour." (Dccerabcr, 1880)^ in wbich the physiologieal action of the vimal puijtle 
wiiB diiCU8»ed ; it» function Is here srated to be n pho^o-ehcmiml one, desif^ed to aeci^rti- 
mc^d^ maion to dijfetetti tttprtea of Htfht, since it U CApable of chiDging and rf«gaiiiiiig lt» 
original color when circumptanees dcroand it (an intenaity^f light or axi approach to 
ikrkneu ctuaing rapid effects upou it). 



THE VISUAL PURPLE, 



868 



fancrioB is may yet be considered a subject of investiga- 
loti. A prominent author says of this matter; ''It is very 
ipting to connect this visual purple with color vision ; but 






P flO, 87«— A. I'ertiraf nrHion o/ th« retina. 
<n.M tiller) 



B. dmttertioH of thv nnU and cohia n/ 
the retina teilh tJu nervous eleincnU. 
(S<ipiX7.) 

1, 1, Inrrr nf rod* mnd conefi; 2. itwln; S, eone«; 4^ 4, 6, 6, exlernAl granule Infer: 
*i, nlo U?cr (cone-fiber plcxtua); H, tut^^rnnl i^ninule lay^r; », 10^ fim-tv 

U s Uvcri n, Uvor of norvc celb; 12, 12, 12, 12, \\, II, filnra of tlir 

; 4, ft» «♦ Podft, ftido view ; 1, 1, 8, 8, ecll» nf 

«^: 9» wll, c*itinecii>fl lijr a fikinent with gnh. 

ifl with e(?llfl of th*' i^ninute InyiTS; 11, 3^1, 

111 un<l internal pmnnie lnyeni (12 1* not la 

% Ii>, 2u, 'i2^ liS, 24, 2fl, 20, A rod and it cone, c*rti- 



1. 1, •> **» rtMliii An<t ittn***, 

J- 
Ah 

Hn! ri^urvi , 14, J 



frniit v|»^« 



tiectod wttb the Ci.^ 



r :inuli' Uvfr*, wlUi the ncnrc ce|l&» &nd with the ncrvu 



enow that our color vision is most exact in the form cen^ 
raff 8^ where the retina consists of cones alone, whlc»h are des- 
Itute of this visual purple/*' 



Mleh. FcMief, <{p. fit. 



TBE VHAJMA.L J^^Ml/cA 



While no positive statements can as yet be made as to I 
function of that layer of the retina known as **ib^f«id»l 
cones of Jacob," still authorities seem inclined loaitiik^t 
the cones^ luther than to the rods, the power i>f juamfitl 
color. It is known that these cones are absent in tl« 
of nocturnal animals ; while, in the eyes of birds and f^f(it| 
globules containing color are found mrhin the cone.^ tel 
over, the *' fovea centralis'* in the human eye is destitute #| 
rods. 

To explain our perception of color, the hyjjotheewwBftfcl 
made by Young that there existed in the retina thepoi««^| 
perceiving three distmci color sensafio/ijf^ wliich, b«ii|C{i» 
of the spectrum, could, by a proper admixture of c^alaui pv] 
portions of each, produce white ; he further suppooied tkj 
there existed three distinct sets qf nerreJlAers^ «- ^ 
sensitive to a i>rimary color sensation, viz., to v.^, 
of a certain length, Hebnholtz has done mtieh to I 
theory to notice, so that the theory is known now as i 
*' Young' Helmholtz theory,'- mther than by the name erf 
originator of the hypothesis alone. The fact that rht? 
ciiref ul microscopical examinations of the retina fail lo ^ 
cover the existence of sets of fibers, which differ in thein 
tomictd construction, seems to place this theory rather on 
basis of a jjretty hypothesis than that of an acknowl 
fact 

Hering and Aubert ' have discarded the Yonn^-Helml 
theory, however, and have attempted to explain the 
tion of c^olor by a process of diHimieffrali^n^ in om? art 
coloi*s, and, In another, by a process of assimilaJioH iA \ 
property of the retina, which is denominated ** m^nal iwl^ 
stance.'^ 

All persons vary much in their power of di^* ' r 
and appreciating color;' but only those can properly it .-^ 
to be ** color blind ^ who regard colors as similar whirli 
most people would be glaringly distinct Thus, red and i 



■in. ff^ 




COLOR VISION. 



865 




366 THE CRANIAL NERVES, 

are commonly mistaken for each other ; whUe purjik d 
blue, red and brown, and brown and green, are often dett^r: 
from one another with difficnlty, if at all. ' 

APPARENT VISION OP OBJECTS NOT REALLY SEEN. 

Any stimulation of the optic nerve or of the retina, if sii 
ciently intense, may give rise to certain sensations, which J^ 
mistaken for actual vision. As examples of this fact, a 1! * 
in the eye or on the back of the skull will often make tt 
injured person "see stars" or have jBashes of light appaMi; 
cross the field of vision. 

Foster' mentions a case, where, by a voluntary ctnupr*- 
sion of tlie eyeball by the orbicularis pwilpebrarum miiN>. 
gorgeous visions of flowers and landscapes could be proilutv: 

EFFECT OF OPTIC NERVE ON COORDINATION. 

The optic nerve may become a means of vertiiro, wl-: 
objects are caused to pass rapidly before the field of visi-i 
as in viewing a waterfall, being rapidly whirled, etc. TLi- 
subject, however, will be more fully considered, with ]-in- 
of interest i)ertaining to the auditory nerve, since Menie>' 
malady is more often dependent upon disease of the acono' 
apparatus. 

Goltz ' has shown, by experiments upon birds whose h^il- 
were artificially secured in an abnormal position, that thevs: 
once become incapable of orderly flight, thus further confirm- 
ing the apparent connection between the special sense of sk*' 
and those muscular movements which require the exercis*^ of 
th(* power of coordination. 

EFFIHT OF TUE OITK^ XEKVE OX THE LACIIRtMAL APPARAir?. 

The contraction of the orbicularis muscle tends to prv^* 
the tears, which the lachrymal canals contain, onwanl towar: 
tht* na.sil duct: and they dilate to receive a fi-esh quantiry 
during tlie ivhixation of this muscle. Thus the act of itini 

* Taylor*s " Scientific Memoirs.'* * Op. ciL 

' I*tiuger*s *' Archiv," 187:J, as <iuotcd by Foster. 



NERVES OF LACHRYMAL APPARATUS. 3C7 

ing^ which usually precedes any special attempt to see with 
distinctness, l)y calling the orbiculaiis palpebrarum muscle 
into play, assists in cleansing the eye of any excess of tears. 
It has been stated l)y Demtschenko,* that, during the closure 
of the eyelid, a peculiar arrangement of the muscular fibers 
tends to keep the lachi'jnnal canals open, and thus to act as 
an aid to the orbicularis muscle in its mechanical effect. In 




Fio. 89. — Tjtehriimnl and Mrif^minn glands. (pAppcy.) 

1,1, internal wall of the orbit ; '-i, 2, internal portion of tlio orbioulariB palpebrarum ; 3, 
8, attnchnient of this niusele to the orbit ; -1, orifiec for the passjipe of the nasal 
Artery ; B, muscle of Homer ; i\, 0, posterior surfaee of the eyeliils, with the Meil)o- 
niian f;land> ; 7, 7, H, N, 1), «.», lo, luchrmal gland and ducts; 11, II, openIn<;8 of the 
lachrymal ducts. 

addition to this anatomical device, the alternating pressure 
of the Umdo oculi upon the lachrymal sac tends to act as a 
pump, and thus to draw the tears from the globe of the eye.' 
The How of tears, while constant in a state of health, may 
Ih? greatly incn.»as«Ml by a retlex act. Such exciting caiist^s as 
a stimiilati(m of the nasiil mucous mnubnine, the (M»njnnc- 
tiva, tlie optic nerve, and the tongue, and, more forcibly, the 
i^flfect of the emotions, are commonly ]>erceived. It is said 
that venous conyestioa ^z/* ///^^ //r^/r/ is fiMnpu^ntly manifestt»d 
by an excessive j)rodii(*tion of tears." The different efferent 

» HofTman und Schwald's •* B<Ticht," 1H7.'^. 

• Darlinff and Rinney, '* EK-t-ntials of Auatomv," 1S80. 

• Mich. Fo!«ter, op. «'. 



THE CRANIAL NEBVE8. 

nerves, which exert a controlling influence upon the lachry- 
mal apparatus in response to the exciting causes above men- 
tioned, include the lachrymal and orbital bixmches of the fifth 
cranial nen'e and filaments of the cemcal sjnn pathetic' 

Many of the facts pertaining to the optic nerve may, by 
the skillful physician, be made useful in his daOy practice as 
guides to diagnosis • while others are given as exiilanations 
of many phenomena which often occa- 
sion alarm to those not familiar with the 
mechanism of their production. 



-.9 CLINICAL POINTS AFFORDED BY MEANS OF 
THE OPTIC NERVE. 

The optic nen^e has of late acquired 
an importance to the oculist, w*hich is 
based upon the physiological distribution 
of the nerve, but which has to the spe- 
cialist more than a theoretical value, 

jp'io, 90.— y.'- . V t:v»- since, by means of the knowledge af- 

TndnJdcJDlopfZi forded, the diagnosis of the existence of 
Jiort^"fSft''*T*?'^ ^' ^^^^^^^ f'Umors pressing upon the nerve^ 
1, wdia of the ladiryruai «r of locfd pffssuTe frnm } fiflammatoTfj 
PBBPiige^ Roiooth'HDd exudutions, may be not onlv positively 
of the lachrymal sac, made out, but the cxact Situation of the 

pre«entinfc delicate . , 

folds of the mucous pressure often detemimed. 
lar fold biionpng to The hypothescs of \\ ollaston and 
the nai^iLi mucou"* mem* Unyo have been so far confirmed hy later 
investigators, that it may now be quite 
positively stated that an exaet lateral Jialfol each retina de- 
rives its power of vision from one optic tract, and the other 
half from the opposite tract. It has been proven that the 
noji-decussaling JWers of each optic tract supply the sense of 
vision to the outer or temporal side of each retina, and that 
the €leeussating fibers of each optic tract supply the inner or 
nasal side of each retina. When, therefore, the optic ti-act 
of either side is pressed upon, so as to affect the entii^ thick- 

* See expeiime&tfl of Hepzeaatein, Wolferz, Reich, and others. 



VAEIETIES OF HEMIANOPSIA. 

ness of the nerve, and thus to interfere with the action of all 
the fibers which that tract contains, the temporal side of the 
retina of that eye which corresponds to the optic tract affected 
and the nasal side of the retina of the opposite eye will be 
rendered blind, or will be impaired in exact proportion to the 
pressure exerted upon the optic tract. Blindness of the lat- 
eral half of the retina of either eye is termed ''hemiopia" or 
**hemianoi)sia''; and this condition may affect, 1, both eyes 
similarly ; 2, both eyes diametrically. 

When either eye is alone affected with blindness, it indi- 
cates, as a rule, that the optic nerve is pressed ujMm, or other- 
wise impaired, at a point situated hi front of the optic 
chiasm; since, if the optic tmct were the seat of the existing 
trouble, both eyes would l)e affected, as it would be almost 
impossible for the pressure to aft'ect the non-decussating 
fibers, and still leave the decussating fibers of the tract unin- 
jnred, or vice versa. With this as a starting-point in the 
diagnosis, we determine which half of the eye is blind, know- 
ing that, if the nasal side be the (me where vision is lost, the 
pressure must be on the inner side of the nerve, and, if the 
outer or temporal side be blind, that the outer side of the 
nerve is the seat of the disease which is causing the pressure. 
Should both sides of one eye be rendered blind, and no locjil 
cause within the eye be found to exist, then the existence 
of pressure anterior to the optic chiasm, of such a character 
that the entire ncTve is destroyed or impaired, may safely be 
diagnosed. 

Total blindness of one eye is fi-equent evidence of glioma 
or sarcoma within the orbit, as they are the two forms of 
tumors which most fivquently affect that ivgion ; and the 
diagnosis of the pres<mce of this cause will probably be con- 
firmed, in case it exists, by symptoms ref(M*:il)le to paralysis of 
some of the muscles of the eye, since the same i)ressure will 
be also likely to affect either the third, fourth, or sixth nerves. 

The most common forai of *" hemianopsia ■' ' met with, as 

' A Kynonyni for hanio/nn in its pcncrally nocoptoM scnsr, l>i]t si lu'ttiT tt'rm, Hincc it 
means blindness of bslf of the retina, wliilc thu foniier nivanii only lialf vision. 



370 THE CRAXIAL NERVES, 

the result of the pressure of cranial tumors, is where thtt* 
poral half of one eye and the nasal half of the opyHis^it*: 
are ren^lered blind. This clinical fact is supported l»y it- 
anatomical distribution of the fibers of the optic traoi, wU \ 
as before stated, supply the temporal half of the eye* f' 
same side and the nasiil half of the eye of the side oii"-: 
When this condition is met, we know that the optk tin i 
the extension of its fibers backward as far as iLe (*»-iv:'r- 
cortex (Fig. 43), must be involved ui>on the side correspniiii: 
to the eye which is blind in its temporal or outer half [Viz. '1 

In those uncommon cases where the inner or nasal Jr^[f ■ 
each retina is deprived of sight, the existence of x>iv>>iirv. 
the anterior or posterior portions of the optic chiasm may'- 
diagnosed, since the decussating fibers of each optic tr ' 
cross each other at these points only ; and the nasal sil*' - 
each eye being affected proves that the decussating fih^r^: 
each tract must be simultaneously pressed upon, without a2; 
disturbance of the non-decussating fibera. 

In those cases where the outer or temporal sides of h-**- 
retiiia? exhibit evidences of pressure from some caus^ witbh. 
the cranium, the explanation of the mechanism of its ]jn»lu' 
tiou has, uutil c>f late, been involved in obscurity; but it > 
now explained by a curious anatomical relation between r'> 
iuternal carotid arteries (as they assist to form ''the cin'lf ■:' 
Willis-') and the optic nerve.* It will be observed, b y ivfe: 
t^nce to the plates of your anatomy, that the anterior co/hn'- 
niratuirf arlt rj/ ]>asses underneath the optic nerves an<l is 
fnmt of the chiasm, vrhile the main trunks of the can»ti.i 
arteries are adjacent to the chiasm, and curl outwanl fn»ni 
nearly its central point toward its outer edge. Now, in -^ml^* 
(frf/i/tr/'d/ion of the vessels, the atheromatous changes in th** 
arterial coats tend to desti'oy the elasticity of the vessels, anJ 
to either shorten them, or to render them less elastic, an-l 
thus, in this regiim, the arti^ies a(*t as a gatheiing-strin.' 
around the optic (*hiasm, and, by pi-essing uix)n the outer p»r 
tiou of each tract, the mm-th^cussating fibers of each tract a^ 

* An explanation original, I I'clieve, with Professor II. Knapp, of thi< citv. 



CAUSES OF HEMIANOPSIA. 



371 



^, impaired, while the decussating fibers of each tract are not 
. injured, thus accounting for the blindness of the temporal 
. half of each retina.* 




B.A. 



Ao. 91. — A, Xon-d*r%u»aiing fibers of tlie optic tract (colored red on chart); B, Decus- 
Moling fibers of optic tract (colored blue on chart) ; C, Opiie Chiasm ; D, Jieiin i 
(showing nerve distribution to each half); K, Oj4k Nerves; h\ Optic Tracts; 
a' — b', region where pressure may produce " hemianopsia " or " total amaui-osis " of 
one eye; k' — d', region where pn^ssure will result in "hemianopsia" of opposite 
halrefl of the retina of both eyes ; c'— c', region where the constriction of the ves- 
sels of the "circle of Willis" will produce "hemianopsia" of temporal half of the 
retina of both eyes; b' or C, special localities where "hemianopsia" of iJie nasal 
half of the retina of both eyes will ensue from pressure ; C c', b c', region which 
must be entirely destroyed by pressure to produce total blijulnen of both eyes. 

K you will compare Fig. 91 with a preceding diagram 
(Pig. 43), it will enable you, perliaps, to better understand 
the mechanical explanations of the various conditions which 
may result from pressure upon the optic tracts, or upon the 
optic nerves, if in front of the chiasm. You will perceive that 
the non-decussating fibers of each tract, wliich I have colored 
red,' if traced to their distribution, sui)i)ly the outer half of 
the eye of the same side, while the decussating fibers of each 
tract, which I have colored blue,' pass to the inner or nasal 
ride of the opposite eye. You can, therefore, see the reason 

' It might be possible for two tumors, each so situated as to affect the outer side only 
of each optic tract, to produce this condition ; but the prolnibility of such a condition 
erer esbciog in toy special case would be extremely small. 

' Shaded dark in figure, but colored for class demonstration. 

' Kol colored In plate, but reprcwnted by decussating; lines. The presence of color 
for damomt ration to large classes is oftentimes of great assistance. 



372 



THE CEAXIAL XEEVES. 



for the following snramnry of the gnides afforded by partial 
blindness of the retina, in making a diagnosis of the situation 
of cranial tumors : 

1. Total bliiulness of one eye indicates pressure between 
the chiasm and the eye affected, which has destroyed the 
conducting power of both the decussating and non-decussat- 
ing fdiers of the nerve. 

% Total blindness of both eyes seldom occurs in tumor ; * 
but, if it be dependent upon a tumor, it must affect the 
chiasm itself, and have completely destroyed it, 

3. A loss of vision in the nasal half of both eyes indicates 
the existence of a lesion, either in front of or beliind the optic 
chiasm, whicli affects only the decussating fibers of each tract. 

4. A loss of vision in the ua-sal half of one eye and the te^m- 
pond half of tlie other, indicates a lesion of the ojdic tracts or 
its extension backward to the cerebral cortex (Fig. 43), upon 
the side where the temporal half of the retina is destroyed, 
or a cortical lesion of the occipital lobe (probably the cuneus). 

5. A lf)ss iA vision in the temporal half of both eyes indi- 
cates senile degeneratmn of the vessels fonniug the ''circle of 
Willis," which are creating pressure upon the outer side of 
each of the optic tracts. 

The optic nei-ve may be the guide to many diseased comii- 
tions of parts more or less distant. The condition of hyper- 
msthesia of the retina (to which membrane its tenninal fila- 
ments are distributed) may be indicative of congestive diseases 
of the bniin ; of the development of cerel>ral tumors ; and of 
certain mental diseases (as prominently sho^^n in ecstasy, 
hypochondria, etc. \ It also occurs in hysteria, chorea, chronic 
alcoholism, narcotism, the inhalations of certain toxic gases, 
etc. It may frequently l>e the evidence of some local condi- 
tion of the oi>tic apparatus ; hence we meet it in cases of 
congestive and inflammatory conditions of the retina; also 
where an excessive amount of application of vision has been 
demanded, in disease and atrophy of the nerve itself, and ui 
slight compression of the nerve from local causes. 

' Thifl ooDditioD la more oommoalj doe to atrophy of the optic neire und to glauooma. 



rj AMBLYOPIA AND AMAUROSIS. 378 

MB^ When the optic nerve filaments become ancesfhetic^ sight 

^jiA impaired in the exact ratio of the loss of sensibility ; hence 

we speak of the condition of ^' amhlyopia^^^ when the sight is 

^, partly destroyed by this condition, and of " amaurosis " when 

kfthe sight is entirely destroyed. 

. ^ We may consider a loss of sensibility of the optic nerve 

filaments as a symptom of the gravest import, since it indi- 

.^cates either some disease of the brain or some advanced 

^ changes of the nerve itself. The brain conditions which are 

r most liable to produce this condition are as follows : neuro- 

^*. letinitis, which may follow cerebral haemorrhage, cerebral 

~. softening, Bright' s disease, lead poisoning, and syphilis; the 

' various forms of ataxia ; cerebral tumors ; chronic eflfiision 

Into the ventricles ; and hysterical cerebral disorders. 

The local conditions which may result in optic anaesthesia 
: Include inflammation of the retina and the adjoining struc- 
tures ; haemorrhage into the retina ; retinal tumors ; the com- 
pression of glaucoma ; pressure of tumors, in the orbit or 
(Hianium, upon the optic tracts ; thickening of the meninges 
in the vicinity of the optic chiasm ; and traumatism. 

Atrophy and sclerosis of the corpora geniculata may result 
in amaurosis'; lesions of the cerebellum* maybe accompanied 
by symptoms referalJe to the optic apparatus (probably on 
account of the pressure created upon adjoining regions of the 
encephalon) ; and an increase of intra-cranial pressure, from 
any cause, may produce retinal changes. 

THE THIRD OR "MOTOR OCULI" NERVE. 

This nerve has its apparent origin from the inner border of 
the cru8 cerebri. The deep origin of the nerve has l)eon dis- 
cussed in preceding pages, which treat of the? crus cerebri ; 
and also in the introductory pages of this section, to which 
the reader is referred. 

The course of this nerve, after it escapes from the brain, 
is of importance, from the relations which it has with impor- 

* See pegc 872 of this volume. ' See page 235 of this volume. 



374 



TBE CRANIAL NERVES. 



tant structiu^es, and from the ijhy^iulogical phenoraemi pro- 
duced by it. It piercer the dura mater opposite to the aii> 

teriof cUnoid process, in order 
to T^acli the outer wall of the 
cavernous sinus, where it lies 
LO close relation with the fourth 
cmnial neiTe, and the ophthiil- 
mie branch of the fifth cranial 
nerv€\ beiug above thcan both, 
and also with the cavernous 
sinus, which lies internal to it. 
It is in this region that the 
neiTe is joined by filaments 
from the cavernous plexus of 
the sympathetic system. 

The nerve now passes from 
the cavity of the cmniuni by 
means of the sjjfienaklal Jis- 
sure^ having, however, di\ided 
into two branches, before its 
escai>e, called the superior and 
inferior. 

In the sphenoidal fissure, 
these two branches are placed 
between the two heads of the external reetus musch of the 
eyeball, and fi-om this point they pass onward to their re- 
spective distributions, viz., the superior branch to the levator 
palpebrae and the superior rectus muscles, and the inferior 
branch to the inferior oblique^ the inferior rectus, and the in- 
ternal rectus muscles, and, by a small filament, funiishing the 
motrjr root to the ciliary or lenticuhir ganglion of the orbit. 

The third cranial nexTe thus supplies aU of the muscles of 
t?ie eye but two, viz., the superior oblique and the external 
rectus muscles, which derive theh motor power, respectively, 
from the fomih and the sixth nerves. It also supplies 
filaments to the ophthalmic ganglion (which is also chilled 
the ciliary, and the lenticular ganglion), which filaments 



Fio. d'Z,^Di»tribuii<m of the motor ocuii 
communvi. (Uirschlcld.) 

1, trunk of the motor otndi {^mmnnh : 2, 
mtpcrior hratit^h ; U, jUammls w/ne/i 
(hiH f/rnttch jtrwiiW to the mijfttsrior rectuA 
and tfie laffUor paffwhri fupeinorU ; 4, 
branch to ike intcrinxl rrcffitn ; 5* branch 
to the in/erf or rectus ; % hraneh to the 
inferior oblique ntusdc ; 7t branch (o 
the Icniicuiar ifantffion ; 8, motor oculi 
exleruiiA; y^ filaments of tlie niutor 
i>euli cstrmus anastomo^iDgf »itli ihti 
Bjmpatlietic ; 10^ ciliari^ nervts. 



TEE MOTOR OCULI NERVE, 375 

subsequently distributed to the ciliary muscle and the 



iris. 



It is now claimed that the fibers of the third nerve, which 
pass to the aqueduct of Syhius, decussate ; and it is to this 



^'-^<K^ 



1 — 



.\. 



"-^-. 



PiG^ 95. — Cillarff mmde ; magnified 10 dianietera. {Sappey,) 

1,1, ccyfttalliuc luns ; 2, hyaloid meiDbrane ; 8, ^dc of Ziim ; 4, im ; 5, B, one of the 
ciliary procease** ; C, 6, radiaiinp: tilxTs of tbt^ ciliary niui*tlc ; T, tieotion of thts ciicu- 
lar portion of the ciHai^ musek* ; 6, vcdous [tU-xui- of the ciliary process; y, U\ 
*dcrotic onat ; 11,12, coruoa ; 13, epitlielial lavcr of tlae comt.u ; 14, iiienjbraoe of 
Dc'secTnet; Kl, ilgameutiim iiiJis pcctiiiutiuii ; Hi, cpiihcliurn of the Uifmbrunc of 
Detcemet; 17, union of tht- sclomtle coat with the turiRa ; IS, st'ction of the cauiil 
of Schlemm. 

anatomical arrangement of its fibers of origin that the effect of 
the pupil of one eye xipon the condition of the pupil of the 
opposite eye is occasionaUy observed in disease, and that the 
muscles of the two eyes, as well as the iris^ are thus enabled to 
work in perfect harmony with each other. As an exami>le of 
this, it is occasionally observed that, when nmaurosis affects 
one eye, the pupil of the diseased organ will not respond to 
the effect of light upon the retina of that side, but, when the 



370 



THE CBAyiAZ SSBVSA 



light creates a movement of the iris of the nniin !i-! 
the pupil of the opposite side also i^sponds, tUiii* ^h.f^ 
^that reflex action is possible between the two ere^ 

MECHANJNM UF THE < uXtBACTIOK OF TlJ L Vl I'll, 

The mechanism of the reflex act, by which the dM 
nerve is enabled to so affect the contraction of iW p^ 
as to have its varying size correspond exactly to At 
qnirements of the retina, as regards the amouot erf Hi 



Fio. 94. — Choroid coai ^f tht ^^ ami ihf ciliary iktvoiu (fW|HHj} 

I, optic nerve ; 2, 2, 2, 2, a, 8, 3, 4, sclrToiic tni^t, diriMoJ iintl tumftd Imc^ I» 

choroid; 5, 5, 5, 5» the oornfii, divided into four purUon^ «.nd tstuM l«ci.^ 
canal of Schlemtu ; 7, i-vterrml 8urfiit?e of the choroid, trmrcr&<H| by tbc ciikrt w£ 
and one of the lotij? dUrtrv nrtories ; 8, ccntial ve9**el into «rhicli open th» vm ^ 
cosn ; 9, 9, 10, 10, choroid iionc ; 11,11, cilinrv nerve* ; 12, long oliftiy atust; IV 
13, UJ, anterior ciliary drtcHe*; 14, iris ; 15^ 1 5, vascular cirrle of tL« ixU ; 11, 

necessary for perfect vision at all times and under all ditl 

stances, is a subject of interest to those who study 

from the standpoint of its physiological 1 

nerve, when a person comes fnjm dai 

receives, on account of the dilated conditlim of tim^ 

an excess of light which at once compels the eye to 

tarily close* nntil the pupil shall become contrarted 



' A reflex net produced ihrough the optic oi^^rvc upon the oHiictilail« 

Duscle. 




DISTRIBUTION OF THE THIBD NERVE. 



377 



^nsation of oTOr-stimulatiou created in the optic nerve by 

le glare of light entering the dilated pupil is carried back- 

cl to the brain, and, probably in the region of the aque- 

luct of Sylvius, creates a retlex act wliich sends motor Im- 

iuJHe» rJong the fibers of the third nerve to the iris, by means 

the branch to the ciliary ganglion. Thus it happens that, 

rhen the eye is again ojjened, the sensation of distress in the 

>tic nerve is no longer present, and the pupil is found to be 

mtmrted in a dh'ect proportion to the amount of light whi<*h 

the time exists. 

SABONS FOR THE PECrUAa DISTRIBUTION OF THE THIRD XEEVE. 

The distribution of the third cmnial nerve may suggest 
the inquiring mind the following questions : ''Why does 



•Jv 



:>^>i 



tft«— >iteii» o/ eiliary nervn^—XenrM 0/ t/tt m». ( After Sftppcf .) 
^ cborold ; BJHb ; 1, I, 1, 1, liUarr ticrvet c)hJ4tit^ «i llidr tcnitin»l extremitv toto two 

1 ^ foniied bj Uiu ntaA^tomcmid ; 8, 3, ncrFi;* of 



latnfi^ use ihret* urrst^s tu control the mnv^-nipnts of the six 

^ular mu^clcjs, when she could have tised one nerve to accom- 

>lbh the effect i Why are the internal rectus, the inferior 

>bUque, and the inferior rectus supplied from on© nerve 

to the exclnsion of the external rectus, and the supe- 



376 



TUB CBAXIAL NEI^V£.^. 



light creates a movement of the iris of the tmimrain-l 
the pupil of the opposite side also i-esi>onds, Ihus *hu»^J 
that reflex action is possil^le between thr* Twd ev-ps. 

MECHANISM OF TUE COXTIlACTlo:^ OV THE PtPIU 

The mechaTxism of the reflex act, bj which rlw* ti 
nerve is enabled to so aflfect the contrartion of tte pip*] 
as to have its varying size correspond exactly ro tbi^j 
quirements of the retina, as regards the amoani of Mj 



ICL. 



f^t 



'■^ 



.'M 



!>tf:n 



\iiMM 



^^t^ 11 



T^6 



Fig. H.— rAo/'o«</ coat ^ the #|^ a«// /A/ tfiWiirjir h^tvm. (8«fipi^.l 

If opirc norvc ; 2, 2, 2, 2^ 3, 3, 3, 4, Hcbrotic coat^ divided and Itirminj tmv\ 

choroid; 5« 5, 5, 0, the comffi^ divided m%o four poitiun^ umi urm,. 
citniil of Sehleiutn ; 1^ extevntd ^mfstce of the chi>rt 
and one of the lon^ cilmry artfries; 8» wniral v***- 
cosft ; 0, 9, 10, 1*>, choniid Kom; ; 1 1, M, ctliary nt'rvc* i i J 
13, in, anterior ciliary arteries ; H, im ; 15, 15, vamniUr 

necessary for perfect vision at all times and under all cir* 
stances, Is a subject of interest to those who study amUiwy 
from the standpoint of its physiological bean- 
nene, when a jjerson comes from dorkneiss lun* i 
receives, on accoont of the dilated condition of il 

excess of light which at once compels the eye to mm 
tarily close* until the pupil shall hecomi* contract^HL 

' A rcflfis act produced ihrou^b the optie none upoo the wtiieiiltH« 
muscle. 




DISTRIBUTION OF TEE THIRD NEBVE. 



377 



tion of over-stimulation created in the optic nervt? by 
the glai'e of lijGfht entering the dilated pupil is carried back- 
to the brain^ and, probably in the region of the aque- 
uct of Syhdiis, creates a retlex act which sends motor im- 
ulses along the fibers of the thiid nerv e to the iris, by means 
of the branch to the ciliary ganglion. Thus it happens that, 
lien the eye is again opened, the senjsation of distress in the 
ptic nerve is no longer pi^esent, and the pupil is found to be 
ontracted in a diiect proportion to the amount of light which 
the time eadsts. 




IBASON8 FOR THE PECCLIAE DISTRIBUTION OF THE THIRD XERVE, 

The distribution of the third cranial nerve may suggest 
the inquiring mind the following questions; '* Why does 






''m 



Fio, W. — fHfmM o/dliftrjf n«rrf$,—Xenfri of tht km. ( After Supper,) 

ll^; B, lri« ; I, 1» I, 1, olUftrr oenrrs tllndttif? at their tenTtiimi cxtrt'iriitr into two 
ornwre bnmcbt^ vhh h anadtomoft? ro form adreular plcxut* ftuirotmdmg (he irrcalcr 
dreiimfitfciioc of (lie in-*; 2^ 2, pk\u*j fonuctJ bj l)iU ojiaitotnosin ; 3, 3^ nrrve» of 
th^ idi oriKinatlng from iliiii pK tu8, 

Nature use thrw nervt^s to control the movements of the ^ix 
loeular muftcles, when she could have u.Hed one nerve to acconi- 
IpUwh the effect} Why are the int^niHl rectus, the inferior 
jlique, and the Inferior rectus supplied from one nerve 

nourro, to the exduslcm of the external rectus, and the supe- 



THE OE AXIAL XERVES, 



nor oblique muscles ? Furtliermoi-e, why is the iris supplied 
witb TieiTe power froDi the third nen^f , aed not also from the 
fourth nerve or the sixth nerve V 

As was stated in the intniKluetory lecture of this course, 
when touching upon the distribution of nen-es in general, Na- 
ture often indicates, by the distriliution of the nerves, some 
valuable hints as to the physiology of the parts supplied 
by each nerve filament ; and such qtiestions, as are presup- 
posed above, will, if constantly asked by the student of anat- 
omy, often enable him, by close study, to gain not only 
information of a most practical kind, but it will also greatly 
assist him to retain in his memory w^hat would otherwise 
escape, and rentier tins line of study a source of unceasing 
pleasure and interest. 

It is evident, when a glance at the distribution of the mo- 
tor oculi nerve is taken, that it is essentially the nerm of 
accommodation of vision for objects of variable distances 
from the retina. By its contml over the internal muscles of 
the orbit, the eyes can be moved in unison in their endeavor 
to focus objects simultaneously ujion each retina, and thus to 
gain a perception of the solidity of objects, which can not be 
afforded by one eye alone. It is a fact, w^hich perhaps the 
reader has never thought of, thnt the two external recti mus- 
cles, or the two superior ol>bque muscles, are seldom called 
into simidtaneous action, since they both tend to cause 
the eye to roll outward, and thus oppose the natural move- 
ment of the two eyes, one of which usually moves inward 
while the other moves outward, in order to favor the percep- 
ti(m of the same objects by the retina of each eye* For this 
reason alone, it would lie impossible that these two muscles 
of each orl)it should be supplied from the same nerve as 
the other muscles, since they could not possil>ly act in har- 
mony %vith each other. Again, the superior oljlique and the 
external I'ectiis muscles are seldom called into simultaneous 
action except in oblique movements of the eye, and their 
actions are so dissimilar that they have often to act l>oth warh 
and without the aid of the other; hence two neiTes (the 



ACCOMMODATION OF VISION. 



379 




jTsOurth and sixth) are famished so that each muscle can 

^^bave its own source of nerve supply. 

The distribution of the third nerve to the iris affords a still 

>.more beautiful example of the con- 

^.r.stant efforts of Nature to bring all 

. ..parts into a harmony with each oth- 

.. er, and by the simplest means at 

., her control. It has been mentioned, 

: . in connection with the optic nerve, 
that the pupil contracts as the eye 
is drawn inward, and also in at- 
tempts to focus near objects upon 
the retina. Now, the third nei-ve 
is the neiTe by which not only is 
the eye drawn inward, but it is 
also the nerve by which the ciliary 
muscle of the eye is enabled to 
afFect the convexity of the crystal- 
line lens of the eye, and thus to 
act as an adjuster of the focal dis- 
tance of objects whose images fall 
upon the retina. How important 

it is, therefore, that the pupil which is so essentml to the 
proper performance of vision, since it controls the quantity 
of light admitted to the retina, should be placed under the 
same nervous control as the muscles of accommodation of 
vision ! 

MECHAXISM OF THE DILATATION OF THE PUPIL. 

The pupil is made to dilate by means of muscular iibei-s, 
which radiate from the margin of the pupil toward the cir- 
cumference of the iris. It is probable that these lil)ers are 
under the control of the sympat/ietic system ot nerves.* If 
so, it must be observed that the sympathetic nerves have 
an effect up<m the iris directly opposite to that which it 
exercises upon the bl()o<l-vessels, since, when it is stimu- 

' Experiments of Julius Budge, 1851, aud Augiiiitii:> Waller, "Gazette Medieale de 
Pkris.** DiaooTcred by Petit, 1827. 



Fig. 96. — Ciliary nerves^ course 
and terminatioii,. (After Sappey.) 

1, optic nerve, covered by its exter- 
nal or ligamentous envelope; 
2, optic nerve, covered only by 
its proper envelope (neurilem'- 
ma); 3, 3, sclerotic, or fibrous 
envelope of the eyeball : 4, 4, 
xnA ; 6, pupil ; 6, 6, ciliary 
nerves penetrating the scle- 
rotic ; 7, 7, nerves passing be- 
tween sclerotic and choroid ; 8, 
8, plexus resulting from their 
anastomoses ; 9, 9, raniitications 
extending from this plexus into 
the iris. 



380 



TEE CRANIAL SERVES, 



lated, tile pupils are dilated, while the blood-vessels are con- 
tracted. 

Mosso ' has endeavored to show a relation between the tur- 
gescence of the vessels of the iris and the extent of dilatation 
of the pupil which exists at the same time, and thus to avoid 



piQ, 97. — SeHioii oftht lent^ etc.^ ahoming the mechanism of aeeommodaiion. (Fick.) 

Tlie li^ft fiide of tlve Bja^'ire {F^ shows tlie lens adapted to Tision at infinite diitimoea ; the 
Hpht aide of tlic iv^nw {N) shows the lens adapted to the vision of near ohjecu, the 
etJiiirf muscle bdng eoatructud and the ^uapcuHorj ligatnetit of tbt^ Lena coiiBequentlj 
relaxed* 

the apparent inconsistency in the effect of the sympathetic 
system upon the same tyi>e of muscular structure. 

Oehl* and others claim that the sympathetic fibers, which 
act in antagoninm to those of the third nerve ui>on the iris, 
are not derived from the ophthalmic ganglion^ but accompany 
the ophthalmic bi-anch of the fifth cmnial nerve^ and enter the 
eye with the long ciliary nerves ; and that, when these sympa- 
thetic filaments are divided, stimulation uf the main sjTUpa- 
thetic cords no longer causes dihitation of the pupil. He thus 
ascribes to the ^tk cranial nerve the power of dilating the 
pupil, anil regards the Gasserian ganglion as the source from 
wliicli tlds power is derived fi'om the sympathetic system. 

The exjieriments of OeM were made upon dogs and rabbits^ 
and have been confirmed by Rosenthal, Hensen, Volckera, 
and Vulpian. The effect of these fibers of the fifth nerve is 
thought by these observers to be dependent upon a vaso- 
motorial influence upon the blood supply of the iris. 



^ Cl Mosso, Turin, 1876. 



» Ocale imd Melsaner's '* Bericbt,*' IS02, 



THE MOVEMENTS OF THE EYEBALL. 



881 



Slight QsciUatioiis of the pupil may be observed to occur 
synchronously with the action of the heart, and others, ^Iho, 
witli tlie respiratory movements. These oscillations have been 
by some considered as an evidence that the movements of the 
pupil were the result of altemtions in its vascularity, the iris 
rrmtnicting when its vessels are filled, and dilating when its 
vessels are empty ; but the physiological fact that the move- 
ments of contraction and dilatation of the pupil are noticed in 
the Idoodless eye seems to point to some other agency than 
simply an alteration in the blood supply.' 



MOTIONS OF THE EYEBALL. 

Since the third nerve is distributed to all of the muscles 
of the eyeball but two, the motions of the eye are largely 
controlled by it ; wliile accommodation of msioii is also pro- 
duced by its distribution to the ciEary muscle. Some prac- 
tical facts may be here noted respecting the movements of 
the eyeball, which have not only a genenil interest, but a 
diagnostic value. 

The eye is virtually a ball placed in a socket, the orbit 

' ** The impairment of tritie reflei action (* pupillary reflex *) was first inteUipently 
studii7d in 1869, bj Dr. Argyll RoberUon^ of Edinburgh. His observations hftve ^inct' 
beftQ ftbuodautly verified by muueroua observers^ and (w eibauMtive paper on the subject 
baa been published by Professor W, Erb^ of Lf-'ipsic, iti X\m * Archives of Medicine/ Oc- 
tober, 1880. llobei'tsoHf and others after hini, out iced tbal tbe pupils of tabetic patientH 
did not dilate in the aliadow and eoutmet in the lightf as do tionna! pupiln^ and they fur- 
ther observed that during the effort of accommodation there occurred a Dornial pupillary 
t>oQtrajction. In other wordd^ the reflex irig movements wure ftboli>hed, while ttti associa- 
ted qua^i- vol notary movements were preserved. These phenomena may be obseived in 
almoistt all patiemta eufTcTing from posterior j^pinul Hckrosi.-^, and I am in tbe Imbit of call- 
ing the Attention of atudents to tbe symptom. In two of the patients now under my care 
this condition is not present^ but there have been eases of abnormal BclerosU in which all 
the symptoms appeared in a most irregular manner.*' (E. C. Segnin^ " Med, Kceord,'^ 188L) 

"The pupils in a suspected case of posterior-spinal sclerosis are to bo tested in the fol- 
lowing numner: the patient is placed, seated or standing, facing a brightly illuminated 
window, and told to keep hi:* look fixed on some distant object, such as a house or tree. 
By akemately closing and opening the lids, or, better, by shading the eyes with onc*s 
ha.nd momeuturity^ it is easy to see if the pupils change diameter. It is of the utmont 
impprtanoe that the pattcnt^s intelligent assistance be secured, in order tliat bie? garc shall 
remain adjusted for distance. In a given case the absence of reaction to tight having 
been noted, we next htild up one finger or a small object within a foot of the patient^a 
face, and bid him look at it. At once the pupils contract, and do so in proportion to the 
aecommodative effort and the coincident convergence. When the patient looks at the dis- 
tant object, and relatively or absolutely relaxes Ids accommodation, the pupiU dilate again." 
27 



382 



TEE CRANIAL NERVES. 



and the globe forming a ball-and-socket joint. In its socket 
joint, the eye is capable of a variety of movements ; but it can 
not, by any voluntary effort, be moved out of its socket. By 
disease, however, the position of the eyeball within the cavity 



f / 



fy' ; 



2 4 



Fro- 98 — Mmdm of the e^SalL (Sappev.) 

If Attacbmcnt of the tendon ccmnected with the inferior rectus, internal rectiia, and ex- 
ternal rectus; a, external rectuj^» divided and tumet? downw»rd to expose llie inferior 
reetua; 3, internal rectus ; 4, inferior recrus; r», ?iiperi<ir reetus ; ti^ superior oblique; 
7, pttlleT and reflected portion of the superior ublkpie ; W, inferior oblique; 9, levator 
pnlpebnc superions ; U\ 10, middle portion of the levator palpebnr superioiis; 1 1, op- 
tic nerve. 



of the orbit may be materially altered. By pressure on the 
nerves distributed to its muscles, pamlysis of those individual 
muscles may result which are supjilied by the affected nerve, 
and the eye may thus be deflected from its normal position 
by the other muscles, whose motor pow*er is unimpaired. The 
anatomical fact, that the muscles which move the eyeball de- 
rive theii' motor jyower from three sources, viz. : the third, 
fourth, and sixth cranial nen^es, may often be made a means 
of deteiTninuig tlie situation of abnormal conditions within 
the orbit or cranial cavity, by a thorough familiarity with the 
points of origin of each of these nerves, and the relations 
which each bears to tlie surrounding parts throughout the 
whole length of its coui'se. 



THE MOVEMENTS OF THE EYEBALL, 



383 



It has been 8ho\ni by Bonders that, though we can move 
the eye in almost every pt»ssible variety of inclination, we can 
not, by a mlimtary effort, rotate the eyeball around its longi- 
tudinal visual axis. The arrangement of the muscles of the 
eyebaU would seem to permit of such a movement, but we 
can not by any direct effort of will bring it about by itself, 
although we can occasionally produce it unconsciously when 
we endeavor to move the eyeballs in ceitain special directions. 

During movements of the head, the eyes, if directed toward 
an object, may be kept stationary upon that object, in spite of 
such movements of the head," veiy much aB the needle of the 
ship's compass remains stationary when the ship is turned. 
By this wonderful coordination of movement sfeadmess of 
sion is insui^d, which would be otherwise impossible.* 



A TABLE SHOWING THE ACTION OF THE OCL^LAR MUSCLBS. 

Toelsmteth^f^je. J Recto b superior. 



Straight movements. 



Oblique movementSi 



f Obliquiis inferior. 

J Hue t us inferior. 

r Obliqiius superior. 

KectiiB internua, 

RectuR extern 09. 

£ Kerlus superior. 

To ei^oat^ and atlduet tbe eye ) Rectus iutemua. 

' Obliqous inferior. 
Rectus inferior. 
Reetua internum, 
i Obliquus superior, 
^ Rectus (Superior. 

To elevate and t^duet the eye. } Rectus externos, 

( Obliquos inferior* 
t Rectus iuferior. 

To depress and ahdvei the eye ) Rectus extemus. 

( ObliipJU{ii superior. 



To deprtn the eye 

To adduet toward the nasal side. . . 
To addtiet toward the malar side, . 



To depress and addmt the eye* , 



Ib the accompanying table,' in whieb the various motions 
of the eye are enumerfited, and the combinations of muscles 
necessary to produce each of these individual motions are 
shown, it will be perceived that in the straight deflections of 

* An effect due chieflj to the actien of the oblique muscles of tbe eje, 
•Mich, Foster, "Tent-Book of Physiology.** 

• Alter Mich. Foster, cp. di. 



884 



THE CRAmAL NERVES, 



the globe of the eye never more than two muscles are required 
to produce them, and often only one ; whOe, in the oblique 
detlectiijns oi the globe, three muscles are always compelled 
to work in unison. It may furthennore be stated that, to 
counterbalance the action of either of the oblique muscles of 
the eye, two muscleB are always reqiiked. Suppose, for ex- 
ample, that the superior oblique muBcle of the orl>it was para- 
lyzed from pressure upon the fourth nerve, the eye would 
then be dmvra dowmwanl and outward only by the combined 
action of the external and inferior recti muscles, although 
that is the dii^ect line of action of the muscle i:)aralyzed ; while, 
if that muscle should contmct, and thus displace the eye 
downward and outward, the antagonistic muscles would be 
the superior and internal recti muscles, since the former 
would tend to draw the eye upward and inward, while the 
latter would also assist in drawing the eye inward. 

The ability to move either of the eyes independently of the 
other is possessed by very few individuals, although, in rare 
cases, such a power is present. The movements of the eye 
have been so arranged by Nature that the objects seen shall 
affect the corresponding portions of each of the two retinae, in 
order to insui e single vision ; and, for that reason, the two 
eyes will be perceived to move exactly alike, each passing 
simultaneously to the left or to the right, upward or down- 
ward. 

It is evident, therefore, when we throw into action the 
rectus internus of one eye, that we use the rectus extemus of 
the opposite eye, and vice versa, in case the object to be fo- 
cused upon the retinae lies away from the median line of the 
head ; but, if it lies in the direct line of vision, but so close to 
the face as to require a muscular effort to focus it upon the 
i-etina?, then the two internal recti muscles are called into 
simultaneous action. Finally, in case the object to be per- 
ceived lies at a distance from the eyes, it becomes necessary 
for the eyes to be brought into nearly a condUion ofpaTaUel' 
wm^ to accomplish which the two external recti muscles are 
called into simultaneous action. 



CENTER FOR OCULAR MOVEMENTS. 



385 



5 Such a complex coordination of movement as the various 
\r. positions of the eyes demand would seem to indicate that a 
p? special arrangement had been made within the component 
*. parts of the brain to provide for its control, and thus insure 




KBXt 



rstm> Kini 



Fie. 99. — Diagram thmoing the axes of rotation of the eyebaU, (After Pick.) 

Hie hla/ck linen indicate the direction of the power applied by each of the six ocular mus- 
cles. The dotted line* indicate the axis of rotation of the eyeball. The axis of rota- 
tion for the rectus eztemuK and rectus intemus muscles, being perpendicular lo the 
page^ con not be shown in the diagram. 

that harmony which is absolutely required. The experiments 
of Adamiik * tend to designate the tubercula quadrigemina as 
provided with distinct centers, which control certain move- 
ments of the eyes. Thus, he finds in the nates (the upi)er 
X)ortion of the tuberciilaquadrigemina) a common center' for 
both eyes, stimulation of the right side producing movements 
of both eyes to the left, of the left side, movements to the 
right ; while stimulation of the middle line, behind, causes a 

> Quoted by Flint, Foster, and others. 

* For details ooooemiDg subdi? isions of the nuclei of origin of the third nerre, OOD- 
mII a pntkNis pa^e of thit Tolume. 



886 



THE CRANIAL NERVES. 



dowBward movement of both eyes, with a eonvergence of the 
axes, andj if made in front, an npward movement with a return 
to parallelism, both of which effects are accompanied by the 
movements of the pupil naturally associated with them* 

The third nerve has a decided importance in affording ns 
one means of determining the distance of objects from the 
retinae which perceive them, \iz., the muscular sense. It has 
been previously stated that, in order to perceive near objects, 
the internal recti and the ciliary muscles of either eye are 
called into simultaneous action, and w*e soon learn to uncon- 
sciously estimate the amount of muscular i:>ower required to 
properly adjust the eye for distinct vision, and thus to use 
the third nerve, as well as the optic nerve^ as a guide to the ac- 
curate determination of distance. 



ALTERATION OF THE POSITION OF THE HEAD FBOM PABALYSI8 OF 
THE OCULAR MUSCLES, 

It is a fact weU known among oculists, and one which 
often helps them materially in diagnosis, that the defects 
of vision, occasioned by impairment in the power of some of 
the muscles, which control the eyeball, cause the patients un- 
consciously to assume a position of the head which tends to 
assist them in the use of the affected eye. So diagnostic are 
some of the attitudes assumed by this class of afflicted i>eople, 
that the condition which exists may be told at a glance, as 
the patient enters a room, by one thoroughly familiar ^dth 
the diseases of this important organ. The explanation of tliis 
tendency, on the pari of this class of patients, lies in the fact 
that any loss of power in the ocular muscles immediat*?ly 
shows itself in the perception of every object, as it were, 
doubled ; and it is to overcome these double images that 
patients almost instantaneously discover their ability to get 
rid of the annoyance by some special attitude, which, of 
course, depends upon the muscle which is weakened or para- 
lyzed. 

It will be necessary, in order to make you clearly under- 
stand the mechanism of this peculiarity^ that the separate 



5 ABNORMAL ATTITUDE FROM OCULAR PARESIS. 387 

.. action of the six muscles which directly act upon the globe of 
^ the eye be considered. 

p The action of each of the ocular muscles may be given, 
,. then, as follows, with the proviso that many of the motions 
,^ of the eye are not the result of the contraction of any single 
J muscle, but often of a number acting either in unison or sue- 
; oessively. 

[. The superior obliqtte muscle turns the eye downward and 
outward. 

The inferior oblique muscle turns the eye upward and 
outward. 

The superior rectus muscle turns the eye upward and 
inward. 

The inferior rectus muscle turns the eye downward and 
inward. 

The internal rectus muscle turns the eye directly inward. 
The external rectus muscle turns the eye directly outward. 
This statement as to the above muscles reveals nothing 
which would not be immediately suggested by the insertion 
of each, with the exception of the superior and inferior recti 
muscles, which, besides the action which their situation 
would naturally suggest^ tend also to draw the eyeball in- 
wardj on account of the obliquity of the axis of the orbit and 
the same obliquity of the muscles, since they arise at the apex 
of the orbit. The action of the oblique muscles is, as any one 
&miliar with their origin and insertion would naturally sur- 
mise, to control the oblique movements of the eyeball. 

Now, as soon as any one of these six muscles l)ec()mes 
pressed upon and weakened by the presence of tumors, in- 
flammatory exudation, syphilis, or other causes, the patient 
at once perceives double images^ and, in order to get his eye 
into such a relative positicm with that of the healthy side as 
to enable them both to focus upon the same object in a natu- 
ral manner, the patient soon learns to so move liis head as to 
compel the two eyes to look in parallel directions. 

A very simple rule can be suggested by which you may be 
enabled, not only to tell in what dii-ecticm a patient would move 



388 



THE CRANIAL NERVES, 



hifl head in case any special muscle be rendered weak or utter- 
ly useless, but also to diagnose the muscle affected, when you 
look at the patient, mtliout any knowledge of his history. 
The rule may be thus stated : In paresis of any of the ocu- 
lar muscles^ the head is so deflected froni its no^rmal post- 
tlon that the cMu is carried in a direction corresponding to 
the action of the affected mnscl^\ 

Thus, in paresis of the external rectus,* the chin would be 
earned outward toward the injured muscle; while, in paresis 
of the internal rectus muscle, the head would be turned away 
from the side on which the muscle fails to act. In case the 
superior oblique muscle is impaired, the chin would be carried 
downward and outward ; %vMle, in the case of the inferior 
oblique muscle, the chin would have to be moved upward 
and laitward to benefit the vision of the patient. The supe- 
rior and inferior recti muscles, when impaired by disease or 
other causes, would likewise create a deflection of the head in 
a line corresponding to that of theu' respective actions^ 



CLINICAL POINTS OF INTEREST PERTAINING TQ TUB THIED NEBVB. 

Paresis of the external and internal recti muscles causes, in 
addition to the facts already described, aoother point of very 
great value in diagnosis, viz.^ an alteration in the appareid 
size of the objects seen from what they would be iu health. 
The condition of vision, termed by oculists ^^Tneffalopsia^^ or 
^^maeropsiay^^ signifies pai*esis of the external rectus; while 
the opposite condition, called ''//^/t^rop^/a," indicates loss of 
jiower in the internal rectus muscle. 

In the former of these conditions, the objects seen by the 
patient seem to be greater in jioint of size than the intelligence 
of the patient assures him is the case ; wMe, in the latter, 
objects seem smaller to the patient than they really are. 

To explain to you Just how these variations of vision are 

1 While this sUtcmont would be absolutctj true in theory id all casee^ we inust 
ftcknowledgc^ as a dintcal fact, that patients learn to utUrl^ dinrcffard the imago in the 
effected eye, wliun the hitrrmti or extemai reolma is the Bctl of paresis, and to use the nor- 
mal eye only tor the purposes of visioOf thus rendering this attitude of the head le» dlag- 
noatic than when the oblique muscles are affected. 



7A10PSIA AND MianOP^lA, 



laiocomplislied may require a more extended discussion of the 
pliysiologic'ul problems of vision than an anatomical discus- 
sion can properly deal with ; but, to understand it, you must 
know that th<^ apparent size of any object depends upon 
the ability of the person to properly and accurately aj?preci- 
<Ue the angle formed Itetween mys of light coming frnm the 
object and entering the pupils of each eye, or, in other words, 
tlie distance at which the object is placed from the retina. 
Now, in the case of paresis of the external rectus muscle, the 
object is caused to ap]»ear nearer tc» the eye than it really is, 
and thus to be larger than normal vision would cause it to 
seem, since tlie angle of the axes of vision is greater ; while, 
in caae of the paralysis of the internal oblique, the object is 
apparently much farther removed from the eye than it really 
is, and thustlie intelligence construes it as of smaller si^e than 
it would if the visual perceptions were ncmuaL 

There is only one other condition of the eye where the size 
of objects perceived by the retina is either increased or mark- 
edly diminished, if the actual size be taken as a standard of 
measiirement, and this condition is one of inllammation of the 
choi-oid coat of the eye. It is a well-recr»gnized fact that, in 
the effusi-ceformot choroiditis, objects are perceived as much 
smaller than they reidly are, while in cicatricial choroiditis 
the size of the object is magnified. 

These phenomena can not be explained as the result of a 
change in the angle of the axis of vision, since n<» thing exists 
to disturb the perception of distance ; I)ut it is attiibuted to a 
separation, in the one case, and to an aggregation in tlie 
other, of the cone^ of the retina. 

The eye, l)y constant use, has become enabled to partly 
e-Stimate the size of objects by the number of cones in the 
retina which are covered by the image of the object. Thus, 
when, from causes such as have been mentioned above, the 
elements of the retina- are either huddled more closely to- 
gether by a cicatrix i>f the choroid coat of the eye, or dissem- 
inated over a larger space than they normally occupy by an 
effusion of tlie i*hc>roid cnat, the numher of cones covered by 



390 



TBE CRAHUL NERVES. 



the image thrown upon the retina is either increased^ thus 
apparently magnifying the size of the object, or the number 

of cones affected is decreased, and thus the size of the object 
aeen is apparently diminished. 




B. CantirrfioTi of tht rods and conea of 
thf retina with the nentmtg elanenU. 



TlQ. 100. — A. VtTfieaf xifUon of the retina. 
(H. Miilk^r.) 

(Sappey.) 

A. 1, 1, layer of roils and cones; 2, rods; 8, conen; 4, 4, B, fl, extem&l granule lnver; 

7, inter-pranii!e lnyer (con^fiber pl*»xus); R, internal granule layer; fl, 10^ finelj 
f^nmiiUr pmy layer; II, layer of nerve cells; 12, \% 12» 12, 14, H, fibers of Uic 
optic nerve ; 13, mciiibrantt liniitans. 

B. I, 1, 2, S, rodi* and cone.*, front view; 4, f>| 6, ro(!s» Bide view; 7» 7, 8, 8, &A\^ of 

the <*xtemttl ami intemnj pninulc layers ; i*, eell, connected Uy a filament witli snK- 
jaccnt oell^; 10, 13, nerve ct^lb, conne<'ted witli ecllji of thi^ ^rafiiile layer?; II, 21, 
Slamenta eonneetin*^ cells of the extrrnal and intt^mal ii^anulc lavere (12 is not in 
the fispire); U, 15, 16, 17, 18, 19, ti\ 22, 23, 24, 2ft, 26, n mil "and a cone, c«in- 
in'cted with the cells of the f^ranule layers, with the nervo ccUt?, nnd with the nerve 
fibers. 



In cases where comj)lete blindness, even to the sensation 
of light, exists, as sometimes occurs in amaurosis,' the eyes 



* For the causes of this csondltion, see psge 873 of this volume. 



PARALYSIS OF THE THIRD NERVE. 391 

^remain fixed and immovable, gaadng steadily forward, even 
^ when objects are made to pass before the vision ; while in 
cases of partial blindness, which prevent the i)erception of 
outline, but still allow of the i)erception of passing objects 
between the light and the retinse, by the shadow which they 
throw, the eye involuntarily moves in a direction which cor- 
zesponds to that of the moving object. 

Cases in which the third nerve has been impaired by pres- 
sure or disease, or totally destroyed by section, are character- 
ised by a foiling of the upper eyelid over the pupil,' and an 
ioability to raise it, owing to the inaction of its levator mus- 
cle^ so that the eye appears constantly half shut. This con- 
dUiom is known by the name of ^^ptosisy The movements 
of the eyeball are also nearly suspended, and permanent ex- 
temal strabUmtis takes place, owing to the paralysis of the 
laftemal rectus muscle, while the external rectus, animated by 
a dilEerent nerve, preserves its activity. From i)aralysis of 
the fibers distributed to the iris, a dilataiion of the pupil is 
also iiroduced, and accommodation of the injured eye for near 
objects is no longer performed. 

While the upper eyelid is jyartially raised by the levator 
pali>ebi» muscle, which is supplied by the third nerve, it is 
also raised by means of muscular fibers, which are governed 
by the cervical symjxathetic. A similar set of fibers exists in 
the lower eyelid, and is governed by the same nerves ; and it 
is probably through the influence of the sympathetic system 
that the eye is opened. In the act of winking, where the 
shutting of the eye is usually affected more rapidly than the 
opening, a contrast is afforded between the action of the cra- 
nial nerves and those of the sympathetic, since closing of the 
eye is performed by the facial nerve.* 

External strabismus may often occur without the condi- 
tion of "ptosis" being present, the filament to the levator 
jMdpebrae muscle not being affected. 

When all the muscles supplied by the third nerve are 

* 80 marked la thia deformity that the upper lid frequently almoRt touches the 
lower lid. * Mich. Foster, op, cU, 



THE CRANIAL NEBYE8. 

pamlyzed, the globe of the eye is slightly protmded, 
relaxation of most of its muscles. 

In strabismus, or squint^ an optical defect' is iisuallj 
present. So large is the percentage of optical error in tho3 
cases where the eyes turn inward toward the nose, that thi 
condition seldom exists without an accompanying hyi)eropii 
or far-sightedness, due to a diminution of the antero-posteric 
^axis of the eye ; while in external squint, where the eye lool 

ray from the nose, the opi>osite condition of myopia, 
near-sightedness, is often present, but perhaps not in as h 
a percentage of cases as in the opposite deflection of the eye 
For this reason, operations ai^e often of little benefit wht! 
performed for the relief of strabismus, unless the error in 
vision Is accurately determined and corrected by the appro- 
priate lenses. 



DISEASES OF THE OOULAB MITSCLES AND THEIR CAUSES. 

The muscles of the orbit may present the conditions 
spasm, contnu'ture, motor irritation, or i>amlysis. 

The condition of '' npstaffmus^^ is characterized by clon^ 
spasm of the external ocular muscles, and by peculiar osci 
tions or involuntary movements of the organ. It is always i 
bilateral atfection, and its starting-point, according to the ei 
periments of Adamuk and Ferrier,' seems to be situated witl 

' Sec Hiijiica W^alton, Steltwag, and others. In Bpenking of this optical derKl,d«»jH 
dent upon t^imple hyp4*rupia, Dr, Loring say?^ in an article previously quoted in titi* rol- 
unie : *' I have known boya of i.^ight or ten years of age to beg their parents to let them 
undergo the pain of an operation to rid themselves of a dpforroity which subjeciti them m 
often to the unfeeling remarke of their elders, usually friends of the family^ «a well aa 
the uneuphonious but expressive titles bestowed upon them by their own oontcmporsriofl, 
of goggle-eye and cock-eye. Nor docs this end with childhood. The defomaty is a diA- 
advantage to him through life. It pursues him in his business ami in lil^ profc^lcoi. 
Cheated of feature by disdembllng nature, he U often thought to be diateinbling himself, 
when nothing U further from his thought?. Bow oftvn do we hear people iay of another, 
wliom we know to be perfectly upright and trustworthy, that they do not like lum bccmuit 
he never looks them squarely in the face ! And it is a little curious that pr«?ciicly here it 
U that the lesser degrees of the trouble produce the most effect. That peculiar esproaaian 
which people complain so much of is generally due to a deviation In th« axes of the eym 
— € slight convergence, which is never very conspicuous, and at times only to be deiecied 
' a trained eye, but which, nevertheless, produces in all a Tcry dJjtogrecablo iinproMioat 

ough not marked enough to l}etra7 its ca^ise*** 

* Disouaaed in the previous section. 




CAUSES OF PARALYSIS OF THE THIRD NERVE. 393 

the anterior tubercula quadrigemina. It may be produced by 
causes affecting either the central nerve ganglia, the periphe- 
ral nerves, the refracting media of the eye, or the retina. We 
thus find it existing in connection with meningitis, hydro- 
cephalus, etc., in uterine diseases, worms, dentition, caries 
of the teeth, etc., and in some of the diseases of the eye or 
optic nerve. 

Sjyasm of the^er* of the iris is observed, in rare cases, to 
exist in connection with some irritative condition of the cere- 
bro-spinal system, which has involved the cilio-spinal center 
of the spinal cord.* 

By corUracture of a muscle is meant a permanent shorten- 
ing, in contrast to its temporary shortening when under the 
ordinary influence of the motor stimulus. It occurs, in the 
ocular group of muscles, as the result of the direct irritation 
following some pathological process, at a seat more or less 
distant from the orbit ; or as the eflfect of prolonged paralysis 
of some of the antagonistic muscles. 

In those cerebral and spinal conditions in which convxdsive 
attacks are produced, and in attacks of hysteria, the evidences 
of well-marked motor irritation of the ocular muscles are 
often observed. 

Paralysis of the ocular group of muscles may vary in 
degree, thus constituting either paresis or true paralysis ; also 
in extent, thus affecting all the muscles supplied by the third 
nerve, and often the fourth and sixth nerves as well, or, again, 
only separate muscles ; and finally in duration and its sus- 
ceptibility to treatment. This symptom may be either an 
initial symptom, or a complication of some central disease, or 
the result of peripheral causes. 

Paralysis of the muscles supplied by the third nerve is 
most frequently produced by the following causes : Circum- 
scribed meningeal processes at the base of the skull ; tu- 
mors, softening, and haemorrhage of the cerebral peduncles ; 
softening and haemorrhage of the cerebral ganglia ; syphi- 

' For det&ilB as to the situation and function of this center, the reader is referred to 
•abteqnent pages of this Tolume. 




m 



lis (aflfecting the cranial or orbital cavity) ; orbital tnmc 
diphtheria ; and, finally, aneurisms (if the carotid (as reporti! 
by Lehert ' ). In the decielopmeni of ataxia^ the thinl ner 
may become paralyzed simultaneously with other nerves of the 
cmnium, or, possibly, without other nerves being affected 
and the same condition may follow the prolonged use of co- 
nium or gelsemlum. 

VVlien the paralysis of the third nerve is produced by intra- 
cranial lesions, the paralj^sis is liable to be bilateral or to lend 
toward a symmetrical development as the disease progress«e; 
while the fourth and sixth nen es are often subsequently af- 
fected. Them are also other symptoms, of great value in 
deciding upon the existence of inti'a-cerebral disease, which 
may be present, such as the coexistence of cephalalgia, ver- 
tigo, sjTnptoms of neuro-retinitis, disturbancas of speech and 
of the intellectual faculties, convulsive raovementii of a laciU_ 
or general type, a sense of weight in the limbs, or, possibl| 
the presence of paresis or paralysis of the muscles of the" 
extremities. 

** A very large proportion of tabetic patients tell of past < 
present diplopia, and, in a certain number of cases, the ociil 
paralysis precedes the pains and ataxia by sevei-al yearn. So 
true is this statement^ that it has become an established ptac- 
tice with neurologists and ophthalmologists to susi>ect posie^ 
rior spinal sclerosis in adults who present themselves mith 
strabismus, diplopia, or ptosis. In such a case we should 
carefully question the patient about the occun'ence of fulgu* 
i-ating pains, and test the pupillary and tendinous reflexes. I 
need hardly add that another obligatory line of inquiry in 
such cases is with reference to symptoms of syphilis."* ' 

The same remarks apply to atrophy of the optic nerve, 
which is occasionally an early symptom. 

It is not infrequent for IfsionH of the spinal cord to pro- 
duce paralysis of the ocular muscles. The presence of siieli 
an exciting cause may be surmised by the coexistence of ingiie 
neuralgias in the bninches of the cervical or brachial plexnsea, 

I Quoted hf RoaenOud. « E. €. Seguin, '' tfed. Ri«ord,** imu 



THE FOURTH CRANIAL NERVE. 395 

or in the sciatic nerves ; of abnormal sensations in the back, 
knees, and soles Of the feet ; seminal emissions, frequent or 
prolonged erections, or diminished sexual i)ower; extreme 
sensitiveness to moisture of the atmosphere or winds; a 
tendency to fatigue, often present after a night's rei)ose; 
and an increase in the galvano-excitability of the main nen-e 
trunks. 

Paralysis of the ocular muscles may accompany glosso- 
lahiO'pharyngeaZ paralysis (Duchenne's disease*), if the cen- 
ter for the movements of the eye be affected at the same time 
as the centers of the muscles of speech and deglutition ; in 
this case, the third and sixth nerves are frequently affected 
simultaneously. The same condition of the ocular muscles 
may also accompany ataxic symptoms of cerebral origin. 

Rheumatism may produce ocular paralysis. This cause is 
to be suspected when no symptoms exist which seem to point 
to local trouble in the orbit or brain. It is found to affect the 
motor oculi and the abducens nerves more frequently than the 
patheticus. 

Diplopia and strabismus are often the first symptoms of 
cei-ebral diseases or ataxia, since they may appear before tlie 
other parts of the muscular system are affected. If they show, 
at times, a tendency toward spontaneous retrogression, and 
again return with the simultaneous occurrence of neuralgic 
pain, the development of a cerebral lesion is rendered still 
more probable. 



THE FOURTH (TROCHLEAR OR PATHETIC) NERVE. 

The apparent origin of this nerve is from the superior 
peduncle of the cerebellum^ and it then winds around it, pass- 
ing close to the i)osterior border of the pons Varolii. The 
deep fibers of this nerve may be traced to four different situ- 
ations, as follows : 1, some to the substance of the peduncle ; 

* The symptoms of this condition will be found mentioned in more detail in conneo- 
tioii with the hypogiossal nenre. 



sm 



TBE CRANIAL NERVES. 



2, other fibers to the valve of Vieussens^ where they are lost, 
with the exception of a few, which can be traced to theXrenu^ 
lum ; 8, a few fibers to the tuber cula quadrigemina ; 4, a 
large bundle, which pass inward toward the median line and 
then deeussaie vvith corresponding iilaments of the opposite 
side. The nncleas of the nerve is shown in Fig. 75. 

This decussation of the fibers of the nerve is for the same 
physiological reason, as was mentioned in connection with the 

preceding nerve, viz., to afford 
iKiiTiiony of action between 
the two sides, when the eyes 
are compelled ti) remain fixed 
V ■ :\\ upon an object during move- 
ments of the ttead. 

From the point of appar- 
ent origin, the nerv^e passes ' 
forward along the outer waU 
of the cavernous sinus, where 
it lies below the third nerve \ 
and above the opIitkalm^e^ 
branch of the^Yh nerve, and 
escapes from the cavity of the 
cranium, through the liighest 
part of the sphenoidal fissure, 
into the cavity of the orbit. 
The question of the func- 



FlO. lOl. —Bhtribution of ike pafhrticus. 
(Hii-Bckfeld.) 

I, olfactory nerve; 11, optic nerves^ 11 F^ mo- 
tor fKHill coinTnimis ; IV^ ifathe/iem, htf fhe 
tide of the ophthalmic branch of Ihc Jiff/i^ 
andpamng to the aupn-ior oblique mwtcie; 
VI, motor oculi cxlernua ; l^ Ranglioii of 
Gaaser; 2, 3, 4, 5, 6, 7, S. 9, 10, Ofilithal- 
roie division of tbe fifth nerve, with its* 
branches. 



tinn of this nerve resolves it- 
self simply into the mode of action of the superior oblique 
muscle. ThiH muscle arises just above the inner margin of 
the optic foramen, and pa^sses forward along the upper wall 
of the orbit, at ita inner angle, to a little cartilaginouB ring,, 
which serves as a pulley for its tendon. Its tendon becomes 
rounded just before it passes through this ring, where it makes 
a sharp curve, passes outward and slightly backward, and be- 
comes spre^id out, to be attached to tlie globe, at the superior 
and external part of itvS posterior hemisiiheiN:*. It is, there- 
fore, the direct antagonist of the inferior oblique muscle. 



THE FIFTH CRANIAL NERVE, 



397 



In its fiincrinn, it is purely a motor nerve, but it receives 
a few recurrent fibers from the fifth neri^e^ which are sen- 
soiy, 

WTien this nerve is paralyzed^ the pc^sition trf the eye 
shows no apparent change, except when the head is moved 
fi'om side to side, in which case the eye moves witJt the head* 
tlie absence of the usual conipensi^ting ninveinent vt the eye, 
which accompanies all the movements of the head, being de- 
stroyed in consequence of the paralysis of the superior oblique 
muscle, which gi-eatly assists in this act. The j^atient alsn 
sees a double image, whenever attempts are made to lor^k 
straight forward, or at objects situated toward the paralyzed 
side ; but the image becomes a single one when the head is 
tiimed ttnvard the sound side to view any object ; hence this 
abnormality of attitude of the head is usually present/ 



THE TKIGEMINUS, OR FFFTH NERYE. 

This important nerve has its appai'ent origin within the 
cranium from the lateral aspect of i\\^ pons Varolii^ idthough 
its deep fibers have been traced to distinct nuclei, situated in 
ihBflom of th^ fourth ventricle near to the gray tubercle of 
Rolando and to more distant parts.' It is a mixed nerve, 
having a distinct motor and sensorg root; and thus possesses 
both affejent fibers, through which sensory impressif>ns are 
transmitted to the brain, and efferent fiber's, by which motor 
impulses are transmitted from the brain to the periphery of 
some bmnches of the nerve. 

The intimate relations which the nerve bears with the 
points of origin of the sixth, seventh, eighth, ninth, tenth, 
eleventh, and twelfth cranial nerves in thejloor of the fourth 
ventricle jjossibly exphnn numy of tht>se phenomena which 
are considered as reflex in character, and whose starting-point 

1 For otlier examples ef thiB diaguoatic guide in pamlysm of ocnljir muscles, sec 
previous pages upou the third cranial netre. 

■ See pAge« wMch relate to the rnt^dulla oblongata, tad also preceding pages of ibis 
pectioa tliftt treat of ibe deep origias of the tiltli oervc 
28 





hraneh ; &, ,T'--r^ur 

12, middle cl. p t u^ 
the superficial i' n: " 
of the cnLnial uei vt»». 



,/ fm^if; 11^ imtcnor deep tcmpoml w»r99i 
hir deep tempomt nerre; 14. arfgiit <if 
[ erfidai petitrtM Dorre, I to JCU« rooto 



divides into three large nervous trunks call«*d, resi^ectively, 
rlie oi)hthalmio, the superior maxillary, and the inferior max- 
illary nerves, whirh escape from the cuvity of the cmniam 
through different fomminii.' The ffwtar roof accompanies the 
inferior maxillary nerve until it has escaped from the omnium, 
when it unites with it. 



* The apheoord&l fiftsure^ foniroen rotund nm^ tod forsmcn OTsle rctpMtlvelgr i 
pttdige for tbt«e brttodiefl trvm tb« cmuitm. 



FUNCTIONS OF THE FIFTH NERVE. 



399 



TABLE OF THE DISTRIBUTION OF THE FIFTH CRANIAL NERVE.' 






< 
E 



a. OPHTHAL- 
MIC NERVE. 



(1) Lachbtmal branch. 



^ (8) Nasal branch. 



b. SUPERIOR 
MAXILLARY^ 
NERVE. 



In the mhena-maxil- 
larjfjoaaa. 



In the infrorcrbital 
canal. 



\ Supra-trochlear nerve. 

r Ganglionic nerve (to ciliary ganglion). 
Long ciliary nerves. 
Inf ra-trochlear nerves. 
Internal set. To septum of nose. 

( To mucous mem- 
External set. < brane and integu- 

^ ( mcnt of nose. 

Orbital or Temporo-malar nerve. 

Spheno-palatine nerves (to Meckers gan- 
glion). 

Posterior dental j ^"P^ficial dental 
nerve 1 branches. 

( Deep dental branches. 

Anterior dental nerve. 



On (he face. 



^ Palpebral branches. 
• Nasal branches. 
I Labial branches. 



c, INFERIOR 
MAXILLARY 
NERVE. 



From the 
trunk. 



r f (1) Masseteric branch. 

/o\ n— .» ..wn/^n., S Anterior branch. 
anterior ] (2) I>«p temporal, j p^^^^^ ^^^^ 

(3) Buccal branch. 

j Internal branch. 
External branch. 
[ Auricular. 
( Temporal. 
From the po^erior\ (2) Gustatory nerve 

trunk (Mylo-hyoid. 

(8) Interior dental I Incisor. 
NERVE. I Mental. 

I I t Dental. 



(4) Pterygoid. 

r(l) AURICULO 



tem- 
poral NERVE. 



Prom anatomical points which have been mentioned, and 
also by the above table, the fact is shown that the ophthalmic 
and the superior maxillary nerves possess no motor power, 
while the inferior maxillary nerve is both motor and sensory 
in its function. It has been mentioned in previous pages, 
however, that a vaso-Tnotorial influence is possessed by the 
ophthalmic nerve, and also a direct i)ower of dilating the 
pupils ; but these efl'ects are unquestionably dependent upon 
filaments given to it by the sympathetic nene. 

The ultimate distribution of the three branches of the fifth 
nerve may possibly be made more clear by grouping together 
the efferent and afferent fibers, and thus separating the parts 



I Copied from *' Essentials of Anatomy" (Darling and Ranncy), New York, ISSa 



•100 



TUE CRANIAL NERVES. 



% 



V 



# 



r'l 



[>>>-_ y^ 



^^^ 



Fig. lOa, — ^4 oTia^ram </ /A^ diilri&u/kMt of tht fifih neroe} 

1^ the crt« emthri ; 2, the Jtenmrff rmt of tbe nerve ; S, the rn/tf^r nupt nt the nr-nre ; 4, 
the Oastsenan gajh^Uon, it f ion thr ,*eni!»on' root only ; 6, iht txplUhftisnic noTPf, poastog 
through the rfphenoidat lis sure ; iS, thf mtfurrior marillat^y na'v^, fiMsio^ tllf^Qgh tSit 
formnen rotundum, to eiitiT the Bphfrio-maxUljiry foajyi ; 7, the inferfior maxi&srf 
ntn^^*^ panning thnuj'^ti the rornmeit ovak< in (%)nipntiy «viih the motor rtkot, frhlcll 
soon ji»in.H it ; 8, ii Hbrut'nt Kt^nt backward frtmi thi* ophthalmic ni'rv«« to ih^ IcsKk 
rium cewbelli ; 9, the /ro«/a/ nerve ; 10, the Iachr*/miv nrriv ; 11, the mual mtn 
12« the supm-o7'bital H4*nu\ pusmig throuf];h tho foramen of the iiamc nmme; IS, 1 
Itupt'ft'tt'orMraf nrrife ; 11, the /ony rt7i«r// fwfni*i^» to the \r\^ \ 15^ the Im^icufnr. 
ciiiai'tf ffantfium ; 16» the tt^mi»f>r<t~mttlar «/rw, tfhoiting itn tltvi^iuti into n 
bmnoh am] the mjiHr bninch ; ['7^ ihc Aph^mufntf of ini' nm?ni^ punj!; tn \' 
plion ; 1 % the pntttrnnf dental nrrta, given off jtisi Iwfore the jtupcri- ' acr 

eaters the infra-orbitnl canal, after pas<»irig through thi* ^phiMnvm^i i : 1 

the mitrrior tfmfn^ nrt'tfcit, jnven off m lht> anlruin ; 20, the 
caping at the antenor palntttie fomiuon, nfter p»M§iii^ ihnnijiii 
ttnirriof pulaHnt' ttrrvr^, aftrr * -< » ■ r^ / fr..,., <».,. t^.v,*, r-j^.r t,i' 
flwjp tf/npyrtti nerpf : 2H, tht- 
ftlBo fitippHo^ tht* extcmiil pt. 

to the Internal pterygoid mtisclt; ; 26, tli« p^tMi^rrxitt* ^MtltJine »*r^t*, l*itl*^ t**tfapii 
from the posterior palatine fonmn»o, irninc to r)i*» mti-olfi of the soft f»!i1»f<?t "IT, f| 



aHricHlih-tanjMt'ai Hrrvi\ sptitt 
28, llie (fmtahrtf or linffuaf tf 
2V*, the tn/erior dentttt ttefvt, pi-- ; 
teeth of the lower jaw ; 30, the 
nerve; 31, the ehm'dn (ynuHtHi nei 
ing to it the mrcffithn oj tnttlt : ^i 



n>iddh' 

f»r twothii 

liur dental c 

hram^h of i! 

to the tarotul and mrrrMOMJi pif • u n, ai, thr i 

wrrw, going from Mockers gangiioD to the V'i'lUu* uiujil- Uanylui of th- 
— L, The letiti^ular i^atufUoii, fendiai; filiero to iris mui cilia ry musele; i 

ri - ' '( ; o, tne >' ' ' " v " ,,• tun-rr imm«i 

/ ' ; s, the v'/i/ory fttid i 

t^j^^f-'- ''<''''"' " ^'^' ■' -■-■.,..' j,...^ ... .... -i^, 4iry foftBiU 



Modified froiB Vlower by the tathor. 



DISTEIBUTTON OF THE FIFTH SERVE. 

which are supplied alone with sensation from thoae to which 
the motor root is eventually distributed. 

The ^eretit Jihers of the tifth paii* give m<»t(rr power to 
the muscles of mastication, viz., the temporal^ masseter, and 



m^ 



1 hranr-K fmif* tlt(> nrolor rooi to the iims*ctcr iuiit«cU*- * tiiMisi^Mit* from t^i^ trurifh to 

■d n^rvf ! ft, (rmpttnit hrmifhrn ; 10, r, . runrhm ,* h '«M 

Id/ n^rvf : 12, hnpnat brfmrh ; 13, briiii«:li of tjie motor root to thi« mylo^ 
).? • 1 1, tfi, 1ft, ififerior tfoifa/ n^*t»r, mth its hianchct ; 1(J, incnfai hran^h; 



pterygoids ; also to the myltihycud and anterior bellj* of the 
digastric, and to the t4»nsor iialjiti and tensor tympani. They 
thus cfmtnd not only the y>hy,Hioh>^'enl act of maHfication^ 
but also, to some extent, the acts of drglulition and hearing. 
These fibers furthemiore afford a vaso-7n^t<yr inlluence over 
various ^'esse Is in certaui ivi^ions of the head and face, ^^lecre' 
^*yry fibers Ui the lachrymnl ^dand, and, according to some 



402 



TUE CRANIAL NERVES. 



authors, to the parotid and submaxillary glands, by means of 
fibers derived frrmi the facial nerve (through the chorda tji 
pani branch), are attributed to the trigeminus. By thase fiber 
the secretions necessary to the jjerfect perfonnance of the 
parts supplied by the fifth nerve are also placed ander its 
control, thus Ulustrating again that beautiful law of Natur 
in arranging the nerves in accoixlance with harmony of actionl 
Beside the efferent fibers possessed by the fifth nerve, there 
exist in addition ceitain unnamed fibers which contrul the 
pi^oper mitrition of the eye^ nose^ and other porflons of th*- 
face. These latter fibers am not as yet fully ascertained m 
as to be described in detail, but their existence seems iudi- 



f/ / 



Fio. im^^SuptHw maxillary divuion of the fifth, (HlradifeM.) 

I, gaD^lioo of Gftsser; 2, lachrymal brnnrh of the ophtlmlmie division : ^ 

ilhrt/ fhnUhn of ff*f f/th ; A, orbital hrmtch : f>» fachrtftno^pa!p ' r%t ; 

fnafar hraneh : *l^ temporal branch ; H,8phen4>-j>alathf' •'■'.- ^ ■ nvive;] 

great tuperficial petroiiat nerve; 11, fudal nen*c, Han ncrrr; 

IH^ anterior and (wo postti-iar dfifttaf hranthnk; \i^ h >^fmbr^ttt »f 

the alrtrttni* pioctMtg ; 15, terminitl htanehai of iht fupvnoT maiiUar^ t&vUkmi l€i, 
braxidi of the facial. 



cated by the fat^t that, after section of the fifth nerve, the 
cornea beeomas cloudy ; the whole eye becomes infiamed. 
only to subsequently disorganisse ; the mucous membrane of 
the nose is similarly destroyed, and ulcers frequently miike 
their appearance upon the mucous membmne of the li])8 and 
gums. Snellen, however, considers these changes as the ef-. 



AFFERENT FIBERS OF THE FIFTH NBBVE, 



4*ia 



Bcts of the mtchanical irritation of dirt, which the inncoiis 
membranes, no longer possessing sensibility, ait? unable to 
l)erceive. 

The afferent fibers of the fifth nen^e afford general sensa- 
tion to the entire skin of the head and fa^e, except in the 
\occipital region and the back and lower part of the ra// 



P^ 



Il7 



FH3. la^^—fktfirrJiHaf bronekm c/ tht faeial tmd UuJtftK ^Hinwrhfeld.) 

1, (rutd >i{ thf Au^il ; 2^potierior aurieufar nrrve ; 3, (tntnch trhhh U rfrfivi-n fni^n (lu 

niA ; i^oceipifttl htaneh ; 5, (^^hranche» tn ike w **tr ; 7» diffn»* 

-rjf ; 8^ hrrtnrh tn the itttflo*ftt/oid mmdf^ ; 11, «w/v/ , ' hrtrmfh : U\ 

mUffijjQrai hrttnt^hf^ ,• W^fnrndd httmcfu^ ; 1% ftritnehint*} tfu urn; 

18| nOBot^ or BuhorhUat hrnnehfs ; \\Jmrcf%i hrnnch*^ ; lA, h ; 

"', !?<< ' ' ' ' \1 , ctrvkfU brnn^hfA ; IH, >«ti|iurtli ' ' vrnjimuU of 

fi: titttl ncTVca (branduf* of tlii' til' -4, 2A, 26, 27, 

nth; ,.. ..,. , t%, Ln« : '* M H*^^ biunche^! of t. . . -• 

and also to the inucnu.s mriuhmnes of the iiiuutti* with tin? 
extvi>ti()n i»f the posterior pilhir of the fauees and the poste- 

> nilton, ojK cU, 



THE CRANIAL NERVES, 



rior fehird of tli© tongue, which derive their sensatlaQ hf 
means of the glossopharyngeal nerves. 

Tlie acciirary of this statement, iis regards the distribution 
to the integument of the ear, which is now accepted by most 
of the anatomical authors of the present day, was strangely 
attested to by fa<^ts brought under the notice of John IliltonJ 
who was thus enabled clinically to verify the exact distritm- 
tiun of the fifth nerve to the pinna and the auditory camiL 
It seems that an attempt was made by a criminal to kill his 
wife by catting her throat, but that the attempt wa^ not suc- 
cessful, and resulted in seveiing the auricular branch *)f the^ 
second cervical nerve^ which, as well as the fifth cranial nenri 
supplies the ear. An opportunity was thus afforded to e; 
amine, by the use of needle points, the state of sensibility of^ 
the dilfei^ent portions of the ear, and to decide, by the loss 
of sensibility, the exact regions which the second eenical 
nerve 8Ui)plled* It was thus proven that the upper and an/e- 
rior part of the ear, and also the auditory canal ^ wa.s su|>- 
plied by the fifth cranial nerve ; and that, therefore^ th 
parts are in direct nervous communication with the fi>ivh 
temple, face, nose^ teeth, and the tongue. 

It can thus be easily understood why pain in the auricular 
region, as evidenced In cases recited later on, may prove a 
moat valuable diagnostic sign of irritation of some of the other 
branches of the fifth nen-e, distributed to the regions which 
are associated by means of this nerve with the ear, although 
apparently having no anatomical relation with it. 

In tlie partly diagnininuitic i-epresentution of the distri- 
bution of the nerves to the cutaneous surface of the head, the 
outlines of the various regions, represented as suppliefl by 
the different nerves, ai'e as nearly accurate as careful inves 
gatiou can determine them.' It wiU be perceived that ni 
out of the fourteen regions mapped out ujion the head and 
neck, are snpplied with sensation by some of the branches of 

I "Rest ana Piiln," London ^New York» 1870). 

* Aa ibc bo(ttulA.ric9 of the rei^oni} eupfilied by toy iKm* gnttluftll; «b«4( off 1 
neighboring regions, it i:* not well to rely upon Lbe €xirmM area of any r«gion ill 
itie apodal aenaibiUty of any niTri!, 



CUTANEOUS BRANCHES OF TEE FIFTH NERVE. 406 

the ffth cranial nerve^ while the remaining five axe supplied 
by branches of the cervical plexus, with the exception of that 
region to which the great occipital nerve is distributed. 

It can easily be understood, from what has already been 



Fio. 107. — TIu nertfous distribution of the head. (After Flower, but slightly modified.) 

1, region supplied by the supra-orbital branch of the fifth nerve ; 2, region supplied by 
the supratrochlear branch of the fifth nerve ; 8, region supplied by the iu/ra-troch- 
tear branch of the fifth ner\c ; 4, region supplied by the infra-orbital branch of the 
fifth nerve ; 6, region supplied by the buccal branch of the dfth nerve ; 6, region sup- 
plied by the rnetUal branch of the fifth nerve ; 7, region supplied by the suDcr^eial 
cervical from the cervical plexus ; 8, region supplied by the great auricular irom Uie 
cervical plexus ; 0, rc^on supplied by the temporo^malar branch of the fifth nerve ; 
10, region supplied by the tachryinal branch of the fifth nerve ; 11, region supplied 
by the auriculo-tentporat brunch of the fifth nerve; 12, repon supplied by the ffveai 
occipital (a spinal nerve) ; IS, re<non supplied by the small occipital from the cervical 
plexus ; 14, region supplied by the supra-davicular from the cervical plexus. 

said as to the manner of employing the nerves as guides to 
diagnosis, that a careful study of the limits of each of these 
regions of the head may often enable the physician to explain 
symptoms which might otherwise seem obscure; and also 
enable him to use the symptom of local pain., whenever pres- 
ent, as a signal which Nature often gives of disease in parts 
possibly far removed from the seat of pain, but still inti- 
mately connected with it by means of its nervous supply. 

EFFECTS OF SECTION OF THE FIFTH XERVE. 

Many joints of practical value dependent uixm the fifth 
nerve can be better understood when the effects of its divis- 
ion have been considered in detail. If the fifth nerve l)e 
divided, sensation is immediately destroyed in all those 



THE CR AXIAL NERVES. 

portions of the head and fare to which the efferent nerrw? 
ai'e distributed ; the powir of masticatioti is lost ; the secr^j 
tions of the lurhrymal, parotid, and submaxillary glands 
rendered deficient ; the ad of deglutition becomes imper- 
fect, since some of the muscles required for its i>erformanr*» 
are paralyzed, and since the tongue is iinahh to perceive the 
bolus of food, and therefore can not properly direct its 
movements ; and, finally, hearing is, to a certain extent^ 
impaired, since the tensor tympani muscle ' has lost its motor 
power. 

In addition to these direct eifects of sei'tion^ secandar^^ 
resiMs are manifested in those forms of ulceration whic 
have been previously referred to, and, eventually, in the de- 
struction of sight and smell. 

It may be noticed that the effect of section of the fift 
nerve upon the special sense of taste has not been mentiotifHi^ 
It was foimerly supposed that the gustatory fibers of the fifth 
nerve afforded the sense of taste to the antrrior two thirds of 
the tongue ; but it is now ui'ged by many that the fifth nen-^^ 
is simjjly a nerve of sensation U* that organ, and that its filler 
ai^ employed exclusively in the appi^eciation of the sensations 
of touch and feeling, while the true gustatory fibers of that 
portion of the tongue are derived from the chorda ti/mpafd^ 
branch of the facial nerve. In support of this view, case^ hai? 
been observed where the chorda tympani has been affected, 
either by disease or in consequence of injury wthin the 
middle e^ir, and the sense of taste has been impaired ; but, 
the other hand, cases have been also recorded where the fifti 
neiTe was alone dLseased, and yet taste was destroyed in the 
anterior two thirds of the tongue. It is such cases as the 
latter that still lead some physiologists to lielieve that the 
chorda tympani nene only contr<»ls thejfow of the saliva^ and 
that impairment of this secretion inipaii*s or destroys the spe- 
cial sense of taste afforded by the gustatory branch o! the 
fifth nerve. 

* According to Lucac^s ri*eeiit cxperimcntB {" Eeriiii. k1iJi« Wsebr,,^ 187'^X ^ ' 
tjropftoi muscle presides uver tbi* itrr'nnmadtdion for muMwU Unum. 



jBsa. 



NEURALGIA OF THE FIFTH NERVE. 407 

CLIKICAL POINTS AFFORDED BY THE FIFTH NERVE. 

The fifth nerve may be the seat of neuralgia, spasm, or 
paralysis. The type of neuralgia (called tic-douloureux, the 
facial pain of Fothergill, and " prosopalgia ") dependent upon 
the fifth nerve affects only the sensory trunks ; the spasms 
may be of a tonic or clonic type, and are, of course, confined 
to the muscles supplied by the motor branches of the nerve ; 
while the paralytic condition can aflfect the sensory trunks, 
producing anaesthesia of the parts to which the effected nerve 
is distributed, or the motor filaments may be impaired, thus 
destroying the power of normal movement in the muscles of 
mastication and the mylo-hyoid. So many points of clinical 
interest and practical value pertain to these various condi- 
tions that each will be considered somewhat in detail. 

NEURALGIA OF THE TRIGEMINUS NERVE. 

The various forms of tic-douloureux are so commonly met 
with, and prove so obstinate to treatment, as well as distress- 
ing to the patient, that a practical knowledge of the disease 
can not be gained without a careful study of the various 
causes which have been found to produce it. 

Among the reported cases of this affection, there have 
been discovered, as exciting causes, the following conditions : 
Tumors of the middle fossa of the skull or of the base of 
the brain, producing neuralgia so long as irritation only is 
produced, but anaesthesia when degeneration of the nerve 
trunks begins ; accumulations of pus within the cranial cav- 
ity ; tumors of the pons Varolii ; morbid processes in the 
regions adjacent to the ganglion of Gasser ; and aneurism of 
the internal carotid artery * within the sella turcica. Diseases 
of tjie cervical porticm of the spinal cord, if high up, may cre- 
ate neuralgia of the fifth pair, by irritating the fibers of that 
nerve which arise from the lower part of the medulla. Peri- 
ostitis of the bony orifices, through which the various branches 
of the fifth nerve pass, may create such pressure as to produce 

' Romberg's cuae. 



THE CRANIAL NERVES. 



the most severe and persistent neui^lgias ; for this reason trie 
supra-orbital, infra-orbital, zygomatic, superior and inferir^r 
dental bmnches are more liable to be the seat of pain thiiu 
the branches which pass through such large openings as the 
sphenoidal and spheno-maxillary fissui-es/ Exostoses of the 
bones, especially of the upper and lower jaws, may rr ' '\ 
must severe type of neuralgia by pressure upon the ri . r- 
ing nerve trunks. Exposure to cold or dampness will pn> 
duce it, being one of the most frequent of the trivial causes, 
FimiUy, inflammatmy changes in the ganglia 'attached to the 
nerve, the enlargements and nodosities found upon neserted 
nerves, an exostosis of a Avisdom tooth,* caries and osteo- 
phytes of the bony canals through which branches of the 
nen^e pass, and neuroma of the ganglion of Oasser pn)trud- 
ing through the foramen ovale,* have been known to produce 
the most severe nenralgia, 

Tlie symptoms of tic-douloureux are of the most disti*essin^ 
chanicter. The pain is usuaUy extremely violent, and the 
patients will describe it to you as of a burning, pieiTing. nr 
shooting rhamcter. It is liable to be, at first, paroxysmal ; 
but^ if due to organic disease, it may gradually become raoi« 
or less constant. The continuous pain is, however, usually 
limited to certain well-defined spots of extreme sensitivenes?! 
to pressure, which the patient can I'eadily point out to you 
(the '^ptinrta dolorosa'^ of Valleix), Thus, the flrst branch of 
the trigeminus (the ophthalmic) presents six such points, each 
indicating some one of its subdivisions. These are situated, 
respectively, over the supra-orbital fonimen ; in the center of 
the upper eyelid ; a frontal point over the escape of the nen'e 
of the same name ; one at the outer angle of the eye, for the 
lachrymal branch; and twv) at the inner angle of the ey 
upon the nose, representing the inferinr trochlear and 
ethmoidal nerves. 

In the region supplied by the superior maxillarj^ nerv** 
and its branches, there may exist a malar point, an infra- 



1 



* Hyrtl, AS qaoted by Rosenthal. 

* Thompson, oti qtiotec] by Rosentbiil 



* Ciisc« of Carnochun atul WimIL 

* Cbouppc*s ciuie* 



NEURALGIA OF THE FIFTH NERVE. 409 

orbital i)oiiit, a point in the palate, and one on the gum of 
the upper jaw . 

In the region supplied by the inferior maxillary nerve, 
the points of tenderness are situated in front of the tragus 
of the ear (the temporal point) ; one in the parietal region, 
where the frontal, occipital, and temporal nerves meet ; one 
over the temporo-maxillary joint; a point upon the tongue 
for the lingual branch ; and one upon the integument of the 
chin, for the mental nerve. 

Painful points are often detected by pressure in the region 
of the spinous and transverse processes of the cervical verte- 
br» (the "point apophysaire" of Trousseau). 

The^epuncta dolorosa are usually the starting points for 
the pain of the acute paroxysms, from which the pain radiates 
along the course of the nerves of the region affected. In some 
cases, these points of tenderness may, however, be absent, when 
a central origin of the disease may reasonably be suspected. 

The relation of the filaments of the fifth nerve with some 
vaso-Tnotor fibers causes this type of disease to be often asso- 
ciated with certain disorders of secretion, since the vessels of 
the glands of the affected region are liable to dilate after an 
acute paroxysm of pain. We can thus explain the abundant 
flow of tears after an attack of neuralgia of the ophthalmic 
branch ; and of nasal mucus and saliva, when the second and 
third branches of the trigeminus are involved. Profuse sweat- 
ing of the region of the face affected is also sometimes well 
marked both during and after the paroxysm. 

The vaso-motor communication may also explain why we 
have reported cases of local swellinpc, redness, elevation of the 
temperature, and, sometimes, erysipelatous inflammation of 
the affected region ; and why the hair has ])een ()])sen'ed to 
fall out, and the skin to become discolored and roughened. 
Hypertrophy of the cheek has been noticed, as a result of tic- 
douloureux, by Niemeyer, Brodie, Romberg, and Notta ; and 
ophthalmia has been produced by a similar condition ccmfined 
to the first branch of the fifth nerve. When the nene trunks, 
which at first were the seat of neuralgia, become destroyed or 



410 



THE CRAmAL SERVES, 



serioasly Impaired by pressure or granular degeneration, the 
face may undergo atrophy. 

Neuralgias of the ftfth nerve, when due to cerebral tumor. 
are often complicated by other symptoms which greatly as 
in the diagnosis ; among the more prominent of which may h? 
mentioned diplopia, vertigo, chronic ceplialalgia, spasms al 
certain groups of muscles, paralysis of various tj*pes, and t 
absence of the puncta dolorosa, whose situations have already 
been mentioned, 

Tic-douloureux is not to be confounded with pain depen« 
ent upon the decay of teeth, inflammation of the temporofl 
maxillary articulation, tumors of the antrum, or extension of 
inflammation to that cavity from an acute attack of coryza, 
migraine, or the facial pains of le^id p^jisoning, hysteria, 
spinal affections. It is more common in women than in men 
and most frequent between the ages of thirty and fifty. If 
more liable to occur in cold months than when the weather \a 
warm (provided it be not due to actual disease) ; and it nm^ 
foUow traumatism, senile change-s in the blood-vessels, 
malaiial poisoning. 



1^ 1 



SPA83J OrE TO THE TRIGEMINrS KBBTE. 

The jaw may be rendered immovable, as in tetanus, by the 
masseter, temporal^ and pterygoid muscles, all of which are 
supplied with motor p<iwer by the fifth nerve* The same form 
of spasm may be occasionally observed in attacks of hysteiia. 

Clonic spasm of the temporal and masseter muscles, alter- 
nating \nth that of the depressors of the jaw (the mylo-hyoid 
and the anterior belly of the digastric), produces the chatter- 
ing qf the teeth so often seen in the chill of inflammatory dirt- 
eases and fevers and after exposure to cold. 

The pterygoid muscles, by a tonic contraction, may pro- 
duce the ffrinding of the teeth ; a displacement of the jaw 
to one side, during an hysterical paroxysm, which lasted i 
days, is reported by Leube/ 

^ A9 quoM bj Rosenthal: ^ A Clinical TreatiBe of Uie DIaMMt of the HorroiM f 

t«in« (PuudU umaAkUon, New York, 187U). 




SPASM AND PARALYSIS OF THE FIFTH NERVE. 411 

Spasms of the muscles supplied by the trigeminus may be 
the result of apoplexy, cerebral softening, meningeal exuda- 
tion, lesions of the pons Varolii and medulla oblongata, hys- 
teria, epilepsy, tetanus, hydrophobia, tumors irritating the 
ganglion of Qasser, peripheral irritation, reflex causes (as 
dental ipsAn^ ulceration of the tongue or mouth, intestinal or 
uterine irritation, teething, etc.), and rheumatism. 

In rare cases, the depressors of tJiejaw may be the seat of 
localized spasm, in which event the mouth may be kept wide 
oi)en for a longer or shorter period. 

PARALYSIS OF THE TRIGEMINUS NERVE. 

It is a rare occurrence to observe a simultaneous paraly- 
sis of the motor and sensory roots of the trigeminus. An- 
aesthesia of parts supplied by the branches derived from 
the sensory root may occur from central causes, and is i)er- 
haps more frequent than those symptoms dei)endent upon 
lesions involving the motor root. In lesions confined to the 
cerebral ganglia or cortex, however, the motor root is more 
often impaired than the sensory portion, while the sensory 
root, or some of its branches, is frequently affected from 
causes outside of the cranial cavity. 

In studying the condition of trigeminal anaesthesia, it must 
be prefaced that the regions affected, and therefore the results 
of the impaired nervous function, differ with the exciting 
cause, since a central lesion is liable to involve all of the sen- 
sory branches of the nerve ; while an external cause usually 
affects some individual branch. 

The central lesions of this disease comprise apoplectic 
clots; destructive lesions producing ataxia; hysteria; local 
diseases or exudations which involve the large root of the fifth 
nerve between the pons Varolii and the ganglion of Gasser ; 
and lesions of the medulla oblongata, thus affecting its fibers 
of origin. 

The external causes include all forms of traumatism ; 
exi>osure to cold or heat ; surgical procedures ; caries or i)eri- 
ostitis of the bony canals ; suppuration of the soft tissues ad- 



412 



THE CRAKIAL NERVES. 



joining the affected nerve ; local tumors and inflammatory 
exniiations ; and certain blood conditions accompanied by 
nerve sclerosis (cliiefly Norwegian leproBy).* 

The condition of facial anaesthesia may be complete, when 
sensibility to contact, pain, heat, or cold is alx)lished ; or par- 
tial, when extreme impressions cjin be perceived, and often 
differentiated a.s to the i>eculiar character of each. The needle 
points, the compass, and the electric bnish axe all employed 
in the examination t>f such a patient, in order to decide 
as to the extent, character, and degree of ihe existing pa- 
ralysis. 

If the opMhalmle nerve be the seat of anfesthesia, we may i 
observe a contracted state of the piipU,' insensibility of the 
mucous lining and integument of the upper eyelid, insensi- 
bility of the skin of tlie forehead and the extenial and in- 
ferior parts of the nose, and a total absence of the sense of 
contact in the anterior portions of the mucous membrane of 
the nostril. 

If t!ie supermr fnaaniari/ nerve alone be affected, the skin 
and mucous lining of the lower eyelid, the integument of the 
cheek, lower half of the nose, and the corresponding half of 
the upper lip, show an eutire or partial aliolition of sensibility ; 
while the luucous membranes of the middle iind posterior por- 
tions of the nasal cavity, of the roof of the palate, and the en- 
tire soft palate and uvula, are similnrly affected. The teeth 
and gums of the tipper jaw will als<r> be in the aniesthetic con- 
dition. 

If the inferior muTiUary nerve be the seat of disease, with- 
out impairment of the motor root of the nerve, the integument 
of the outer surface of the ear, above the auditory canal,' of 
the temporal region, <if the correspon<Iing half f>f tlie lower 
lip, and in ft'ont oi the temporo-nuixillary articulation, will be 
destitute of Bensibility. The mucous membrane of the corre* 
sponding side of the h»wer lip, tongue^ cheek, tonsil, and gum 
of the lower jaw will Im also anaesthetic, while the teeth of the 

' See Investi^^ntions of Dnniell^L'n iin<i Boock, as quoted by Rosenthal. 

* For effects of nerve iufiueaoes on thr pupil, sea page 879 of tliia voltime, 

• For researches of Hiltou on this poiut, sec page 404 of this volume. 



TROPHW EFFECTS OF TRIGEMINAL PARALYSIS, 413 



w. 



corresponding side of the lower jaw will likewdsa be deprived 
of sensibility. 

If you will recall the pf>ints which were made in reference 
to the eflFecta of section of the trigeminus, you will be better 
able to understand why paralysis of any jwrtion of this nerve 
shoidd be followed by symptoms of late development, due, 
apparently, to some alteration in the nutrition and reactive 
power of the regions supplied by the nerve which is diseased. 
You will remember that the existence of certain unnamed 
fillers, called ''trophic fibers," was mentioned, whose close 
connection with the symi)atlietic nen-e is highly probable, 
and whose function seems to he to control and regulate the 
blood supply of the regions to which they pass. Now, it is 
clinically observed that the paralysis of any of the three 
large branches of the trigeminus is followed by certain ulcer- 
ative and suppmutive processes in the regions rendered anaes- 
thetic, and that these eiTects are the most prominent and 
serious when the ophthalmic nerve is affected. 

Landmann and Bell were the first obsen^ers to point out 
that, in the human subject, purulent destruction of the eye 

as liable to follow pmssure o|>on the trigeminus from tumors 
in the regitm of the ganglion of Gasser; while Magendie 
j[1824). Bock (1844), Snellen (1858), Spencer Watson (1874), 
Samuel (1860), and Meissner have done much to bring the 
results of defective nutriti*m, following impainnent of neiTe 
supply, to professional notice, It might add much to the 

terest of this volume to enter into the details of the inter* 
esting experiments and clinical observation, which have now 
become quite extensive regarding this subject, but it will ex- 
ceed the scope of this course to more than hastily sketch the 

»sult8 obtained. The opinion of Snellen, that the ulceration 
Vif the coniea and the suppurative conjunctivitis which fol- 
lows amesthesia of the ophthalmic nerve were the mechanical 
effects of the irritation of dirt which the conjunctiva was no 
longer capable of perceiving, seems to have been confirmed by 
Watson * and Baerv^inkel,' who found that an artificial cleans- 




**Med. Time*," 1874. 
2» 



> 'Mrcb. f. klin. Med,/' 1874. 



414 



THE CRANIAL KEUTES, 



ing and closure of the eyelids caused recovery, withcSir as 
effect upon the nerv e condition. It wa^ apparently ub^o pmrea* 
by Bock and Samuel that the condition of anfesthesia wa^i not 
necessary to the development of these later processes, resulting 
in destruction of tissue, since the same results wen? observed 
when hyi^ersBsthesia existed. In refei'ence to the coaiBe ol 
the ''trophic fibei-s" of the ophthalmic nerve, the researcbet 
of Meissner and Schifl * seem to locate their situation in the 
centiTil portitm of the nei*ve, since the other parts seem to 
preside over sensation only. Finally, the interesting experi- 
ments of Sinitzin,* made in 1871, show some remarkabli 
effects of the removal of the superior cerv ical ganglion of the 
sympathetic nen e upon trigeminal ophthalmia ; since it was 
often cured when <mce started, and prevented in every 
where it was done before the trigeminus was divided. 

We know, irrespective of the theories of its causation, 
that the destruction of the sensory root of the fifth nerve » 
liable to be followed by destruction of sight, interferenc 
mth the sense of smell, ulceration of the nose and gums, 
tendency to inttammation and abscess of the soft tissues, and 
possibly, to gangrene. 

It is of practical importance, however, to discriminat 
l>etween that form of ti'igeminal aniesthesia dependent upoB 
central lesions and that due to external pressure or disease. 

We may remember that the cejitrcd form is usually con- 
fined to the inferior maxillary jK^rtion of the nerve ; that a 
previous history of cerebral disease will often be found ; tl 
pai*esis or jmralysis of the muscles of the face, tongue, jawi 
or limbs will possibly coexist ; and that, if the lesion be a 
tumor at the base of the cerebrum, cephalalgia^ neuralgias of 
special branches of the trigeminus, and a simultaneous affec- 
tion of some of the adjacent nerves of the cranium may be 
discovered. 

If the cause is outside qf the cranium (provided it be not 
due to syphilis, rheumatic diathesis or traumatism), we maj 
expect to find evidences of the previous existence of absc^^ 

i •• CcntTftibl," \m. • ** Med. Cciitmlbi;' 1 87 i 



DIAGN08TI0 VALUE OF THE FIFTH NERVE. 415 

periostitis of some of the osseous canals through which the 
various branches of the trigeminus pass, or of local tumors 
which are creating pressure upon some nerve trunk or its 
terminal filaments. 

The motor root of the fifth nerve may he impaired from 
the pressure exerted by meningeal exudation, extravasations 
of blood, or tumors within the cranium ; while it is frequently 
involved (after the sensory portion of the trigeminus) during 
the development of some type of basilar affection. The re- 
sults are manifested by a paralysis of the muscles of mastica- 
tion ui)on the side where the nerve is diseased, except the 
buccinator muscle, which derives its motor power from the 
facial nerve. The healthy muscles of the opi)osite side tend 
to crowd the lower jaw toward the affected side of the face 
during mastication, giving a peculiar expression during the 
act of eating. 

DIAGNOSTIC VALUE OF THB FIFTH NERVE, 

To what extent the distribution of the fifth nerve is of 
practical value in diagnosis may be estimated by the perusal 
of the lectures * of Sir John Hilton upon the significance of 
pain and the use of rest as its cure. Cases have been rei)orted 
by Paget, in his lectures on surgical pathology, and also by 
Anstie,' where the hair of the entire scalp has turned white 
after a severe attack of neuralgic headache ; and another is 
reported by Anstie, where the hair of the eyebrow alone be- 
came i)erfectly blanched from pain in that region dependent 
upon the supra-orbital nerve. Hilton reports a case where the 
hair of the temple^ from the irritation excited in the dental 
branches of the fifth nerve through a decayed molar tooth, 
became suddenly gray (the temple being the region supplied 
by the auriculo-temporal branch of the same nen-e) ; and an- 
other where an obstinate form of ulcer in the auditory canal, 
which was very painful, and had withstood all methods of 
treatment, was cured by the extraction of a decayed tooth in 
the upi)er jaw ; again illustrating the fact tliat irritation of 

" "Rest and Pain," London (New York, 1879). • " Lancet," 1866^ 



418 



TffE CRAXfAl NERVES, 



one branch (the dental) can create disease at the seat of dis 
hution of another branch of the same nerve (the anrici 
tempt^ral). 

The temporo-nicucillary artlctdaUon has often been known 
to assume a condition of immobility during an attack of ear- 
ache, and to be immediately relieved by the application of an 
anodyne to the terminal filaments of the fifth nerve in tht 
canal ; thns illustrating the effect of irritiition of one bnuif:li 
(the anriculo-temporal) upon the others vthich supply the 
muscles of mastication, causing them to contract and thus fix 
the joint. 

Again, a furred candition of the lateral haJf of the tanffue 
may almost be considered a pathognomonic »ign of some 
source of irritation to the fifth nerve, which thus manife.^ 
itself in the peripheral distribution of one of its brunches (the 
gustatory nerve). * 

Chronic ulceration of the cornea has also been reported bjr 
Anstie as a symptom produced by some source of irritation of 
the fifth nerve, far removed from the seat of disease. 

The intimate communication of the internal portions of the 
mouth %vith the eye^ ear, and nose often accounts for many 
curious sjnnptoms, which it would be difficult to acrouni for, 
did we not know that pain may be felt at any branrh of a 
nerve, when one of its trunks is irritated. I have, at the 
present time, a patient under my care, who is suffering fnim 
an obstinate ulceration of the tongue, and who had, previous 
to his consulting me, been treated for an inflammatory condi- 
tion of the ear, on account of a constant and severe |min, 
which was considered as separate and distinct from the tn>u- 
ble wliich was, at the same time, affecting his tongue. A 
pie gargle of opium, which I onlered him to hohl for fifteei 
minutes in his mouth at intervals, relieved the sjTnpt*»7i» 
very short time. 

A case is reported by Hilton where an enlarged eervk 
gland api)eared with a simultaneous discharge fiom the mh 
ditory canal^ and where the explanati<in, by which a decayed 

' firftnsbj CoojKT ; Jobn Hilton, 



\\ in 



DIAGNOSTIC VALUE OF THE FIFTH NERVE. 417 

tooth waa diagnosed as the cause of the condition, was as 
follows: The irritated dental branches of the fifth nerve 
caused an inflammation of the auditory canal, which is sup- 
plied by another branch (the auricular of the auriculo-tem- 
ix)ral) ; this inflammation was followed by suppuration 
and excoriation of that canal, and, subsequently, by ab- 
sorption of the discharges by the lymphatic vessels, thus 
producing the enlarged gland of the neck. This expla- 
nation may seem a roundabout way of reaching a diagnosis, 
but the result of drawing the tooth proved, in this case, 
how well anatomy may guide us, if we only follow its teach- 
ings. 

Earache may not always be due to the fifth nerve, even 
when it is confined to the external portion of the organ, 
since the second cervical nerve supplies the lower aqd hacJc 
part of the external ear, so that pain in that region should 
lead us also to look for some cause of irritation to that nerve. 

The distribution of nerves to the scalp, as shown in the 
figure on page 405, renders the symptom of pain, in any por- 
tion of the scalp, one which may guide us in looking for its 
cause ; since, if it is confined to the anterior and lateral 
aspects of the head, the fifth nerve is probably affected by 
some source of irritation (and a reference to the cut will tell 
you which branch of the nerve is distributed to the seat of 
jmin), while, if confined to the posterior portion of the scalp, 
the occipital nerves are affected, and disease of the spine may 
be suspected, in the region of the first or second cervical ver- 
tebrae. 

The distribution of the fifth nerve to the conjunctiva^ both 
of the globe of the eye and also of the lids, exhibits, to a 
wonderful degree, the axiom given you in the first lecture of 
the course, as to the harmony of action between the sensory 
nerves of the skin, the muscles adjacent, and the joints which 
they move ; since these parts stand very much in the same 
general relation to each other, if the movable point in the 
eyelids be taken as a joint, and the muscles of the lids as 
those which move it. 



418 



THE CRAmAL NEIiVES. 



An analogy has been drawn by a prominent author' 
betM^een a common two-rooted spinal nene and a graat 
''compound nerve -'of the head, whose sens&ry root corr^ 
sponds to the sensory portion of the fifth nerre, and whose 
motirr root comprises the third, fourth, fifth (ita motor 
>rtion), sixth, and seventh cranial nerves, whicli, t^igether^ 
form the motor root of this compound nerve. Mast of the 
reflex acts which are exhibited in the regions of the head 
and the upper portion of the neck can be explained l)y 
the free coramunieaticm which exists between the sea-^sory 
root of this ''compound nene" and its diffeivnt motor 
branches. 

It seems useless to further incorporate such cases, which 
go to prove that only by n thorough familiarity with anat- 
omy are we enabled to explain the many phenomena which 
often puzzle the practitioner ; and that, if we will but use it 
as a guide, diagnosis may be greatly simplified, and an msy 
remedy often discovei*ed for the symptoms* 

SURGICAL ANATOMY OF THE FIFTH KEBVE, 

Surgical operations are often demanded for the reJief 
those toimenting neuralgias which affect the branches of I 
fifth nerve. 

The simple division of a nerve is, at present, seldcim p 
ticed, owing to the certainty of prompt reunion of the nerve 
divided. Resection of not less than two inches qf its lenfftA 
is usually required to make reunion imiKJSsible, or very re- 
mote in point of time. It lias been proposed to turn the pe- 
ripheral extremity of the nerve backward after section, or to 
interpose muscle or fascia, to prevent the possibility of union/ 
Exposui'e and stretching of spinal neixes for the relief of m^n- 
Kilgia have been proposed by Von Nussbaum, but an* not 
usually practiced upon the cranial nerves. * 

The supra'Orbital iierce may be thus divided : 

Pass a naiTow knife, subcutaneously, fnmi a i>oint t 
thi*ee lines on the inner side of the supraorbital notch 

» John Uillou, ♦• He^i ai»d Pain.'* « S. W, MUch^^lK 




^■L 



SURGICAL ANATOMY OF THE FIFTH NERVE. 419 

ward, nntil the point has passed beyond the notch ; then turn 
the blade backward, and cut down to the bone. To resect 
the nerve, make a one-inch incision above and parallel to the 
supra-orbital arch ; seize the cut ends of the nerve in the 
wound, and remove it to the desired extent.* 

To excise the superior mcLxillary nerve^ a crucial incision 
is made over the ivfra-orhital foramen^ and, by the use of a 
small trephine, the anterior waU of the antrum is opened so as 
to include the foramen. The lower wall of the infra-orbital 
canal is now broken with a chisel as far as the spheno- 
maxillary fossa, and the nerve is then dimded at the fora- 
men rotundum with a pair of scissors sharply curved. 
Meckel's ganglion is frequently removed with the excised 
nerve.* 

To divide the inferior dental nerve, the incision may be 
made within the mouth or externally. If the trunk is to be 
removed, before the nerve enters the canal in the lower jaw, 
the external incision is made from the sigrnoid notch to the 
edge of the jaw. The parotid gland is then turned backward, 
and the lower portion of the masseter muscle detached. A 
section of bone is now removed with a trephine, and the dental 
artery is tied, in case it be wounded ; the nerve may then 
be divided, and a half inch of it, which will be found to be 
exi)06ed, resected. 

In the intra-huccal operation, the comer of the mouth is 
held wide oi)en, and an incision one inch in length is made 
along the anterior part of the ramus of the jaw, through the 
fibers of the internal pterygoid muscle. This muscle is then 
loosened from the periosteum by the finger, where the nerve 
can be easily felt, at its entrance into thei dental canal, and 
there divided. 

THE GANGLIA CONNECTED WITH THE FIFTH NERVE. 

In the cut which illustrates the distribution of the branches 
of the fifth nerve will be perceived four ganglionic enlarge- 

' J. N. Warren. * J. R. Wood. 



420 



THE CRANIAL KERYE3. 



nients, exclusive of the ganglion of Gasser^ which are con* 
nected with the nerve, and which have a most iniportam 
function as regards the tissues to which these bmnohes an! 
distributed. | 

As you will notice, the first is connected with the ophthal- 
mic di\ision, and is situated within tlie orbit. It is called th** 
** ophthalmic gfinglion,- ' from its attachment; also the 'Men- 
ticular ganglion," from its shape ; and the '* ciliary ganglion,* 
since it gives off the cUiary nerves to the iris and the musci 
of accommodation of vision. Like all the ganglia of the s; 
jjathetii; nerve, it has a motor root^ a sensory foof^ and a sp. 
pathetic root^ and it furnishes branches of distrihuiion to 
neigli}>oring parts. 

The second is called ** Meckel's gsmglion/' after its discor« 
erer; and the *'spheno-ijalatine ganglion/' since it is chiell; 
disfril>uted to the region of the palate. It is situated in the 
spheno-maxillary fossa, and sends branches to the orbit, 
nose, hard and soft palate. It lies in close i-elation with tin* 
superior niaxiliary nerve. 

The third is called the '*otic ganglion." It lies upon the 
infenor maxillary nerve beUw the foramen aeals, and 8en<1s 
bmnches to the two tensor muscles, viz., the tensor tymini! 
and the tensor palatL It is thus physiologically associati 
with the acts of hearing and (Uglutition. 

The fourth is called the *' submaxillary ganglion/' since it 
lies above the submaxillary gland. It is by means of the dis- 
tribution of the chorda tympani nerve to this ganglion that 
some physiologists attemf>t to explain the appai'ent efT* » t 
which that nen^e has upon the sense of taste in the anterior 
tw*o thirds of the tongue. ' 

The foUomng table* will perhaps a.ssisr you in rememlw 
ing the special points of e^ich of these ganglia, ns it shows the 
various s<jurce3 of supply to each, as well as branches of dis- 
tribution : 



•M 



■4 



^ See preriouB portion of thU chapter, where the gtittatorx ocnre id 
* After Keen. 



THE ABDUOEUrS, OR SIXTH NERVE, 



421 



THE GANGLIA OF THE FIFTH CRANIAL NERVE. 





NaiM. 


Sitoatloa. I SeiHory root 


Motor root. 


root. 


BmchMofdlrtillnitioB. 




OPHTHAL- 
MIC or 
CILIAKY. 

MECKEL'8 

SPHENO- 
PALATINE. 


Between the 
optic nerve 

and eort. 

reetut. 


©TH inuiv»— 
Naeal 
bnmcb. 


8d kkrv*. 

7th xbbve, 
through Vidi- 
an and large 

iHctl OSill 

branches. 

7tu mbkvv, 

through Httall 

pttrosaf. 

6th MKKVK. 

through hit. 

pterygoid 

branch. 


CAVKftKOrS 
PLEXUS. 


To ciliary mosole and 
Iris. 


< 

I 


Spheno- 

JOMQ. 


6th nsbts— 
8phsno-pafa- 
MfM branches. 


Carotid 
PLKxr8.by 
means of Vi- 
dian nerve. 


Orbital, nasal, naso-pala- 
t*ne, anterior or krge 
palatine, n.iddle or ex- 
ternal palntine. 

Post or I Levator palatl, 
small < AxvftiM uvulc, 

palatine ( Palato-glossos. 


5 


OTIC. 


Below the 

/oratnen 

ovale. 


Aurtculo- 

Umporal 

branch. 


Plexus on the 

MinOLK ME- 
HINOKAL 

artkxt. 


To tensor tympanl and 
tensor palaU muscles. 




SUBMAXIL- 
LARY. 


Above the 
wuhmaail' 
lary gland. 


em KERVB— ; Trn neuvk. 
Lingual or through clior- 
Quniatory da iympani 
branch. , branch. 


Plexus on the 

FACIAL 


To submaxillary irland 
of the mouth. 



By reference to the above table, you will perceive that the 
sensory root of each of the four ganglia is derived from the 
fifth cranial nerve by means of some of its branches ; that 
the motor root is derived, in three cases out of four, from the 
seventh cranial nerve ; and, finally, that in every case is the 
sympathetic root derived from v^pleocus upon some neighbor- 
ing blood-vessel. 



THE ABDUCEN8, OR SIXTH NERVE (MOTOR OCULI EXTERNUS). 

The apparent origin of this nerve is from a groove between 
the anterior pyramid of the medulla oblongata and the pos- 
terior border of the pon^ Varolii, The nerve may be said to 
possess two roots, one of which can be traced into the pyra- 
midal body of the medulla, and the other into the pons Va- 
rolii itself. This latter root is sometimes wanting. 

Its deep origin has been tniced by Lockhart ('larke to a 
nucleus in the gray matter of the fourth ventricle of the bmin, 
on the outer side of the locus cceruUtis, 

This nerve is purely motor in its functicm, and is distribu- 
ted to the external rectus muscle of the eye. 



423 



THE CRAXIAL NERVES. 



The most careful researches of Vulpian have as yet 
to discover any decussation of the deep fibers of this nerve^ 
and there would seem to be a 
pliysiological explanation for 
the absence of such an arrange- 
ment, since the two external ^^^^^ 
recti muscles are seldom called MkA^^^^EV -V 
into simultaneous action/ and 
the normal movements of the 
eyes are opposed to such a i>o- 
sition as would ensue if they 
should act in common. 

The sixth nerve anasto- 
moses with the sympathetic 
n-erve in the cavernous sinus, 
where it receives filaments from 
both the carotid plexus and 
from Meckel's ganglion ; and a 
few sensory hlament-s are said 
to be given to it in this local- 
ity from the ophthalmic branch of the fifth cranial nerve. 

Occasionally, this nerve sends a filament to the ophthalm 
gangUor}^ and thus to the iriH^ and it is claimed by Lcm, 
that this arrangement (w hich is an exceptional one) exists in 
those cases of paralysis of the motor ocnli nerve in which 
there is no apparent effect produced upon the mobility of the 
pupil. 

This nerve has no practical importance to the diagnosticiA] 
save the one fact that, in case it be paralyzed, the eye will 
present the condition of internal strabismus; that the ap- 
parent size ot the objects perceived by the retina is magni- 
fied ;* and that the head will be so deflected as to avoid the 
perception of double images.' 

The explanation of both of these effects, as the result of 

* Aft«r tbe cres bttvc been drawn inward, u in AttcmpU to focQi tamx obj^di, that* 
muscles help to restore the axet» of visiao to a Btate of pdralldisni. 

* For explanation of this Etjmptom, the reftder b referred to {Mige SSe of tills 

* See page 886 of this volume 



Fio. \m,—DUitibuiioH >\f f/wf iiio«0r 
aiamus. (ITir9c(ifeld.) 

1, tnink of the motor nciili contmutili^ i 
tl:* bmuche,-^ (2, 3» 4, 5, 0, 7 ) ; «^ f 
oeuH fsternwt^ pamiiny t^ th^ 
rer(»M mititcU ; 9, jSlttmeniv of iAt « 
o«*u/i riferfius anmtftmoaiim^ milk 
9ifmpatkdie ; 10, dliary aenw. 



be J 




TRE FACIAL. OR SEVEXTH XERVK 423 

paress of coiam cMmlar mosclesw has already be^n given in 
the prerioos lemue upon the third cranial neire, and need 
not be aain lepeated. It should not be forgotten, however* 
that internal soabismos is not always dae to paralysis of the 
external rectus mnscle, bnt may indicate a condition of con- 
genital or acquired hyj^eiopia, causiqg a weakness of the ex- 
ternal rectos moscla 



THE FACIAL. OR SEVESTH XERTt 

This nerve has its apparent origin bom a grooft between 
the olitarjf and rt^{form bodies ci the meduUa oblongata* 
and« like the three preceding, has its chief origin in a gray 
nu^ev4 in the floor of the fourth ventricle* in the upper half 
of that space near to the postero-median fissure/ The fila- 
ments of origin, within the substance of the meduUa oblongata* 
may be traced as a fan-like expansion upon the floor of the 
fourth ventricle, scMue of which terminate in the gray nucleus^ 
above described, of the same side as that on which the nerve 
escapes* while other fibers may be seen to decu^sa/e^ thus 
passing to the nucleus of the opposite side. No filaments 
have as yet been sarisfactorily traced upward beyond the 
limits of the medulla.* This nerve accompanies the nerve of 
hearing throughout the whole length of the internal auditory 
CQTial^ and there communicates with it by a few filaments. It 
then enters a curved canal within the temporal bone* called 
the aquedurt of FaU.opiuJf. where it gives off the three petro- 
sal nerves and the chorda tympani branch* whc>5e i-hysioli^- 
cal action has been already considered in connection with the 
fifth nerve. From this canal* it escajies throuirh the ^tyli^ 
VMUtoid foramen^ having, before its exit* civrn a ryniivanio 

* Vttkimn riarie. An xftxiwn yjrxj^ rj itdi vtrrt — i^: " *-*< / '•*"«^«wr;r *"— 

tjBfiaat Bcrve Jkn af«rwr fadal B<3ciei« «ii<v« is :h< psd. 

• TW 4e>?p vkcft 'd 'ike Ir^r* i :h^ ftcil zr-.n^ -rrr* :•: b^r^ *. cf x-=rf«:VA w:sh 
Ike vpfer purrnM of t''^ *rx«t r.iloo ■ t* «r..:.-»r- \' :h^ c-ih::..-*: fs.'L* nr-rVcr-: =^ rnf^^ 



4M 



Ta£ CRAMAL NEliVEX 



branch to the ear.' In the i-egion of the stylo- mastoid fora- 
men, it (xmimHnicatcs with five nerMSy namely, the 
mirieuhu* ui branch of the cervical plexus), the auriculo-tem*^ 



>AH 



Sv\ 



M 



U^ 



Fio. im^-anptrfieUd hrmtthm a/ HU/ncto/ wtd ihtjijtk (Hind^feld.) 

1, tnmk o/(h faekd / % potUH^r awrMlar ncrw ; S, bf>anth tfihieh ii fwtwtiw /rone i 
cmvmil pima ; 4, oeetfdtd bramA : fi, <!. hran^t» to iht mtudea ofthf rar ; 1, (^^^^^ 
trk hramhm ; 8, branch Ho 0m M^^AyoMf murfilr » 0, mtptriar tti*mif»ai &rancA ; IQ 
Umpo/rol hrantha ; U, fronlnf hrttnehn ; 12, ftrmwAflr ^> thr orhicuUriM pulpa&rarH 
18, fiotolt or tmhofhitMd hranehfn ; H, friMw>a/ hrancHm ; 15, ir»/<Tfor trrminal bram^i 
Id, nmiial branekm ; 17, *vrtnW/ ftrrtn^-ACT ; 18, superfidal icmjKirftl nerr^ (br«iicll ' 
of the ftflh); 19, SO, frontal tiirtri s (bmnchM of the fifth); 21, n, 2S, 24. SA, $4, 
St, hraiiGh«fl of the fifth ; 23, 39, 30, 31, 82, brknchc» ol iho cervical oerrcB. 



poral (a bmurh of the fifth nerve), the pnenmoga^tric, tH 

glossopharyngeal, and the oft2*otid plexus of the sympathetic j 

and, siihseqTiently, it divides and is distributed to the mus€h3J 

The facial is the great motor nerve of the muscles of the 

* OooABioiyillj also tlw/Zammf ^/ ^ om m u me aium to the pnftitmogs^Ho oonrt. 



DISTRIBUTIOX OF FACIAL NBRVK 425 

face; hence the neire of expression, ^ It supplies, in addi- 
tion to the facial mnscles^ the muscles of the external ear ; 




Fig. 110. — A Sa^rtan of (ht hmnche* of the facial nerve. 

1, main tnmk of nerre in inteinAl aaditorr ouml ; 2, brmncfaes of commnnicstion with 
AmnoftT XIBTS ; 3, orifice of aquedmet of FaOopiuM ; 4, laiye peiromd nerve ; 6, 
MmaO petrosal nerre ; 4, extermd pehrvai nerve ; 7, fiUments to the laxaU^ ttfmpani 
nnuefe; 8, durrda t^pani nerre; 9, 9tTlo-ma8toid formmen; Xd^poderior auriailar 
nerve ; 11, filament tupp Iring the tl*,1o htioid and digatirie muscles ; 12, the toipobo- 
PACiAL diTiaion of the nerve ; 18, the temt/oral brancfaest ; 14, the malar branches ; 
15, the infra-or&ital branches; 16, the fmeenl brandies; 17, the gMpra-mtniilary 
branches; 18, the infra-maxiUary branches; 19, the ckrtico-pactai. dinsion; 20, 
** iniumeaeeniia gangHoformia"' — the seat of origin of the petrosal nerres. 

three muscles of the neck, namely, the stylo-hvoid, posterior 
beUy of the digastric, and the platysma ; one muscle of the 
middle ear, the stapedius : and one muscle of the palate, the 
levator palati.' By means of the chorda tympani branch, 
it controls the secretion of the i>arotid and submaxillary 
glands, and, possibly, the sense of taste.* By the larjre pe- 

> Sir Charles Bell. 

• Schiff, 1851 ; Bernard. Po!»sibly also some other mu<«cU*?, by mean? of the lingual 
branch, described by Hirscbberg. 

» Sappey ; Hirscbfeld ; A. Flint, Jr. ; J. C. Dalton. The fiU»rs of the ohonia tjmpani 
nerre, by some of the later authoritie!*, are said to .iri-'e fonni an intomu-diatc nerre 
formed by a branch from both the seventh and eighth cranial nerve*, and called the 
''portio intermedia'* or ''nerve of Wrisberg.'' 



THE CR AXIAL NERVES, 



trosal branch, the levator palati and azygos uvnte are sup- 
plied ; and, bj the small petrosal branch, the tensor tjni- 
pani and tensor palati muscles are furnished with motor 
power. 

Several interesting articles have lately appeared upon the 
subject/ 

It is claimed by Vulpiao that the facial nerve also con- 
tains taso-rnotoT fibers^ which are distributed to the veaseli) of 
the tongue and side of the face. 

The effects of paralysis of the facial nerve were tiisi 
brought to professional notice by Sir Charles BelL, who di- 
vided it for facial neumlgia^ and the characteristic deformity 
which restilted is still kno\^Ti under the name of ^'BelFs pa- 
mlysis/' In this c*>ndition, the affected side loses its normal 
expi"ession, and becomes abnormally smooth on account of 
the oblitemtion of the normal lines and wrinkles, due to the 
action of the antagonistic muscles on the healthy side/ The 
patient loses all power of closing the eye of the affected side 
even in sleep, since the orbicularis palpel)rHrum muscle is 
paralyzed ; the mouth is no longer syinraetiical, since it is 
dni>^Ti towanl the healthy side ; the saliva is \*ith difficulty 
retained ; nnd the act of whistling becomes an impossibility, 
as the lips can not be systemtitically governed. This con<li- 
tion may be i^roduced by exposure to severe cold, as in sleigh- 
riding ; by abscess or tumora of the parotid region, aa the 
result of the pressure created ; by diseases of the ear or inju- 
ries to the temjK>ral bone, which impede the free action i\t 
the nerve ; and by cranial lesions. It is pjirticnlarly imp<vr- 
taut that the surgeon should familiarize himself, not only 
with the situation and course of the main trunk of this 
nerve, but also with the course of its branches, previous to 
performing operations about the face, or in the vicinity of 
the mastoid process, and in the upper portions of the 
neck. 

» Vulpian, *'LM»cet;' 1878; H. R. Big«1aw, ♦*Brtin," 1876; E, C. SpiUlm **Medini 
RttoopcJ/* 1880. ^ 

* ncnce the aptness of the remark bj Romberg, ka quoted Uy Uftrnmond, t^Al ** I 
b no better cosmetic for elderly Ladioi tb^i fitiiiil pAnlyfiis,*^ 



DISTRIBUTION OF FACIAL NERVE. 



427 



The distribution of this nerve to the muscles of the palate 
and to the stylo-hyoid explains the impairTaerU of deglutition 
when the facial nerve is paralyzed ; while the filament to the 
stapedius muscle may create modifications in the sense of 
hearing under similar conditions.* 




Fio. m.-^BeWt paraijfmM. (Modified from Corfc.) 



The following tabulated arrangement of the tranches of 
the seventh nerve • will possibly prove of service to you as an 
aid to memory during your student life ; and, as a guide for 
reference or review in your professional labors, such tables 
are always of value : 

' Tbe ientar tjfmpam muade may also be ioToked. 

' Copied from '' Tlie EasentiaL) of Anatomy " : Darling and Ranncy, New York, 1880. 



43S THE CRANIAL NERVES. 



TABXf OF THE BRAKCHSS OF THE FACIAL NERVE. 



» 
> 
^ 
ai 



Ift tbe mtSi9nf eanai. Branch to aaditonr nerre. 

Larpe petroMl (to MeckeTs 






;^ JM».fS^MMlAieMH». 



b the laqimedmd of FdBcphu. 



At tt» exit from the ti^flo-mas' 
sviJ jWwmtMy with the fol- 
loviii^ aerres : 



ganghon). 
Smali pehrotal (to otic gangrnl 
Exterwd petrotal (to nieniDgttl 

plexus). 
Tympanic branch. 
' Great auricular. 
Auriculo-temporal. 
Pncumogastric' 
Glosso-pharjngcal. 
^ Carotid plexus, 
y^ Ob the face. Branches to fifth cranial nerve 



2 ' Ift the dfHAfcctf of FaBopna, 

^ JIKmi{4« V Xe«r the ttjtlo-mMioid fora- 



$ ii^ the face. 



T)fmpanic nerve. 
Chorda tffmpani nenre. 
Posterior auricular nerve. 
Diagastric branch. 
Stjlo-byoid branch. 
lAngwd branch.* 
Temporo-facial nerve. 
Cervico-fadal nerve. 



U yvHi will kx^k at this diagrammatic drawing (Fig. 63), 
YvHi will jH^nvive how simple is the arrangement of the 
^f\9m'^<'s %if iMiHmunication between the facial nerve and the 
Rfrh omnirtl nene and its ganglia. While the drawing is 
iuTon^Uxi ii> Iv purely schematic, still it also illustrates some 
\>( x\u^ anatoniiaU points pertaining to the course and forma- 
tivM\ of tlio Vufian nem\ as well as the relations of the ch^r- 
«:\: tf/ fifhtni nerre to the membrana tympanic as it passes 
thnnich the middle ear to reach the canal of Huguier. 

Thert* is a practical point i^ertaining to the deep origin of 
the tUn^rs of the facial nerve, which may often be of value in 
\ietermiuing the seat of pathological lesions within the sub- 
stauiv of the brain. In hemiplegia, especially in that variety 
wliich is due to haemorrhage, the face is sometimes affected 
uinni the s:ime side as the body and sometimes upon the opix)- 
sitc side, thus being impaired, respectively, either ni)on the 
Hide op[H>site to the cerebral lesion or upon the same side as 
iht^ lesion. To explain these phenomena theoretically, we 

' This cXMunmnicating filament is given off in the aqtteduct of Falhpius as often as at 
iho j»i\K»-iuii.'*toid foramen. 

" IVji^Tibcd by Ilirachberg. Supplies the ttylo^lostuB and palato-glotsHt muscles and 
the tougue. 



CROSSED FACIAL PARALYSIS 



429 



must suppose that the facial nerve fibers are affected by the 
lesion within the brain hrfore they decussate (following them 
from within outward), in case the face is paralyzed on the 
same side as tJie lesion; and that the decussating fibers are 




FiQ, ll2.^A diagram to thaw the relaiioni hdvfeen ihe/neial nerve emd wrMporiumi of the 

fifth nerve^ 

A, Gasserian ganglion ; B, ophtbalmic nerve ; C, superior maxillary nerre ; D, inferior 
maxillary nerve (sensory portion) ; E, inferior maxillary nerve (motor portion) ; M, 
Meckel's ganglion; l^ facial nerve^ entering the aqytdud of FaUopim ; 2, tfi/twiiet- 
eeniia gangUoformie (an enlargement on the nerve) ; 8, facial nerve, following the 
curve of the aqueduct of Fallopius ; i^faeiai nerve, escaping from $^la4naatoid fora^ 
men; 6, large petrosal bran^ joining carotid filament 11 to form the Vidian nerve, 
and entering the Vidian canal ; 6, vnaU, petrosal branch, going to ** otic ganglion '* 10 ; 
7, chorda tympani nerve, escaping from the canal of Bwpiier after winding over the 
upper border of drum membrane of ear, 9 ; 8, guttatorjf nerve, joining with the chorda 
tympani nerve; 9, external drum membratte of the ear; 10, oHc aanaUon; 11, fila- 
menl from carotid plexue to form the Vidian nerve ; 12, the iter ehoraa poeteriut, ad- 
mitting the chorda tympani nerve into the cavity of tlie middle ear. 

pressed upon or destroyed by the lesion, in case the face be 
affected on the same side as the body. 

Now, it has been observed as a pathological fact, that 
when a lesion involves parts of the encephalon anterior to the 
pons Varolii, the phenomena dei)endent upon paralysis of the 
facial nerve are perceived on the same side as the hemiplegia ; 
while, if the lesion be situated either in the lower part * of the 
pons Varolii or below it, the face is paralyzed on the same 
side as the lesion, or on the side opposite to the hemiplegia. 

> Gnbler has shown that the facial nerve Is not paralyzed upon the same side as the 
letioD, if the injury to the pons Varolii be anterior to the imaginary line drawn through 
the point! of escape of the trigemini. 
80 



TBE CUAXJAL NERVES. 



For this reason, the occiirrence of crossed pamlysLs of V^t 
facial nerve ' and body type has been received as a most jkj®- 
tive indication of a lesion situated upon the side of the bnun 
corresjx^nding to the facial paralysis, and either withiji the 
substance of the pons Varolii or in parts of the enrephalon 
posterior to it Such clinical facts as these seem positively to 
indicate that some of the deep libers of the facial nerire paw 
upward into the cerebrum^ and that the decussation of the 
filaments of origin within the floor of the fourth Ventricle is o( I 
little physiological importance compared to these other fibers; ' 
but, unfortunately, no anatomical investigations have, so far, 
discovered fibei-s of this nen e which could be clearly demon^ 
strated as passing upward beyond the pons Varolii. 

It has been often noticed by diffei^nt observers that, in 
case the facial nerve was pamlyzed, the uvula and sqftpulak 
were affected and drawn toward the healthy side by the an- 
tagonistic muscles, whose motor power remained unim|Hiired 
Later investi^^ation has shown, however, that tliis affection ul 
the palate only occurs in those cases of pamlysis due to im- 
paimient of the facial nene witlun the aqueduct qf FaUopiuii 
or fi-om some cmnial lesion which affects its fitammU of 
origin.^ 

The experiments of liemard seem to demonstrate that the 
facial neru\ and not the glosRo-iiliarjngeal alone, is con* 
nected with movements of the velum pula£i\ but not with tbt 
movements of the pillars of the fauces. Tlie construction of 
the small petrosal branch, however, being composed partly of 
fibers derived from the glosso-pharyngeul neiTe, may still 
justify a doubt upon tliis point, 

Hii-sclifeld describes a small filament, which the facial 
nerv^e gives off soon after it emerges from the stylo-mastoid 
foramen, 'Hke liuffual branch^*-* vrh\ch is distributed to the 
tongue and to the styloglosBiis and pakUo-fflossus muscles. 

> A term used to corer those forms of pais^pli wlim Ibe Hue U fwmljMd on ttt 
side opposite to the sltle of the hodjr nffeoted, 

* The petrosal nenrei^ wtijoli cmrty ih§ motor ibon to theao iniiidt» miMt t« impt^mA_ 
lo CAttse ta7 deflection of tiio pdsto. 

* See ubleon fMge ii& 



00MMUNI0ATI0N3 OF FACIAL NERVE. 431 

This may possibly explain the observation of Bernard : that 
paralysis of the facial nerve, after section, produces a devia- 
tion of the tip of tJie tongue; and the same effect has been, at 
different tunes, recorded as the result of paralysis of the fecial 
nerve from intra-cranial causes. 

BBAKGHES OF COMMUKIGATIOK OF THE FACIAL NEBVE. 

Some of the branches of communication which are given 
off by the facial nerve, to join with other nerves, or to be dis- 
tributed to ganglia, are of physiological importance. Thus 
the levator paZati and the azygos uviUce muscles derive their 
motor power from the large petrosal branch after it enters 
Meckel's ganglion;* while the paZato-glossus and palato- 
pJiaryngeus muscles probably derived their motor power 




Fio. 118. — Chorda iympam nerve. (Hinchfeld.) 

If t, S, 4, ftdal Derre passing through the aqueductus Fallopii ; 6, ganglioform enlarge- 
ment ; 6, great petro8al nerve ; 7, spheno-palatine ganglion ; 8, small petrosal nerve ; 
9, thirda tympani; 10, 11, 12, 18, various branches of the facial; 14, 14, Ifi, glosso- 
pharjmgeal nerve. 

from the communicating filament between the facial and the 
glosso-pharyngeal nerves, as shown by Longet. This distribu- 
tion explains, in part, why more or less difficulty is perceived 
in deglntition after division or paralysis of the facial nerve, 
and still more clearly why the pronunciation of certain words 
becomes impaired, and the expulsion of mucus from the back 

1 Oray, Quain, Sappey, and others. 



432 



THE CRANIAL NERVES. 



portion of the mouth and from the pharynx is an art of 
extreme difRciilty. 

The communication of the eemeal plexus with the pad^^ 
rioT auricular branch of the facial affords Bensortf Jilamenb 
to the parts over the muscles which that nerve supplic^^ii. 

The filament of communication between the/aeial nw\ li 
auditory nen es enal>les the muscle of the middle ear siipplifl 
by the facial * to act in harmony with the acoustic api)amtiii$ : 
while the communication between the ^th nerte and the 
facial enables the latter to follow that general axiom* of 
nerve distribution by which the skin over the insertion of 



fO 



FiQ. 114*— J diagrum to th&to the eourac &/ ike lar^ and tmatl p«(ro9ai niryM9 amd db 

Vidimi^ nerves, 

A, atU ganglion ; B, Meckers ganglion ; C, pdrouM parti^m of the tiinpoml bono ; D, p^ 
trims portion of the temporal boae 0^^ ^p^x oorr^spoiidiiig to the carotid cuis) •! 
the base of the skull) ; E^ petrom portion of the temporal bone (its baae cofTeppond* 
log to the external auditory meatus) ; F, pdroxu porthn of the temporal bone (ttf 
superior border^ separatio;; the middle and positerior fo«s« of the »kull>; I. iJMr 
facial firt-iv enteHng the petrous portion of the temporal bone b? meana of tlio ' 
atut audiionuM iniermu '* ; 2, iht facial ncrt*e following the curve of thu **aqiai 
of Fallopius " ; 8, the /am/ nerve eneaping from the temporal Itnne by moans of 1 
**9tjrlo-mn5toi<l foramen" ; 4, the large petrosal ncrvt, oftcuping into the carity of | 
cranium by mean.^ of the *- hiatus Fallopil *^ ; 0, the amall f^trosal nn*vf^ escaping 
the cftvily of the cranium by a foramen of its own ; 6, the *'foramm hatnM «v 
alTortling passage for the lai^e petroftal nerve out of the cranium ; 7, tht ** fw 
ovale," affording passage for the small petrosal nenre out of the craruum, i 
to the otic gaftglit/n ; 8, a filament from the carotid ptrxwi of the sympatbetie I 
joining the largf pctro»af nerre to form the Vidian ncrvf ; 9, the Vidian eamiL tn 
mitting the VuHoh nentt to M«ckeP§ gtrnglim^ B; 10, the Vidian nenrc 

muscles is supplied by the same nerve as the musd^ them* 
selves. 

The commtinication between the facial nerve and the 

1 The Btapediui. * Hilton, " Rest and Pain,*^ See tlao p«g« 18 of thla ▼olnme. 



COMMUNICATIONS OF FACIAL NERVE. 433 

pneumogastric might at first seem, to the casual reader, one 
of accident, rather than of design, on the part of the Creator ; 
but, when we consider how intimately the respiratory func- 
tions and the movements of the face are associated with each 
other, the design at once becomes evident. Paralysis of the 
muscles which dilate the nostrils has been shown to have a 
marked effect upon respiration through the nostril ; and, in 
the horse, which can only breathe through the nose, the effect 
of division of both of the facial nerves is to produce death 
from suffocation, since the nostrils collapse. It was this 
synchronism between the movements of the nostrils and the 
respiratory act that first led Sir Charles Bell * to regard the 
facial nerve as the one which presided over the function of 
respiration, and is still often called one of the ^^respiratory 
nerves qf BelV^ 

A case is reported by this famous investigator where a 
patient, afflicted with unilateral facial paralysis, was obliged 
to lie upon the sound side, and to hold the paralyzed nostril 
open with the fingers, in order to breathe with comfort.' 

The distribution of the facial nerve to the muscles of the 
nose creates an impairment of the sense qf STneU^^ when that 
nerve is injured, since the free entrance of air is interfered 
with. The act of sniffing^ which requires for its complete 
performance a dilated nostril, is rendered almost if not quite 
imx)08sible, and thus a contact of odoriferous substances with 
the mucous membrane of the upper nasal chambers is me- 
chanically interfered with, and acute perception of smell em- 
barrassed. 

BBANCHES OF DISTRIBUTION OF THE FACIAL NERVE. 

The motor branches of the facial to the muscles of the ear 
are of more importance in animals than in man, since the ear 
in the animal becomes capable of perceiving sound with acute- 
ness only by a change in its relative position to the head. 

The stylo-hyoid and the posterior belly of the digastric 
muscles exhibit again the influence of the facial nerve upon 

> " Lcctorei on the Nerrw." * Op.eU. » A. Flint, Jr., op. ciL 



THE CRANIAL NEBYM8. 



the act of deglutition ; and the same remark will apply to 
siylo-glossus muscle. 

WTien the facial nerve haa passed through the fiarotid 
gland, the two branches distributed to the face, riz,, the tern- 
poro-facial and the cervico'facial, become not only motor ta 
their function, but are also supplied with sensory filamenti 
from their communication \^ith other nerves ; so that some of 
their tenninal filaments are distributed to the integument of 
the face, as well as those derived fi*om the J^fih cranial nerpe^ 
which would not be the case were the nerve not 80 supplier! 
with sensory nerve fibers. 

The filament of the facial nerve which snpplies the platy^* 
ma muscle affords a beautiful example of the fact that the 
nerv ous supply of the general muscular system, if carefully 
studied, constantly teaches us points of great physiological 
value as to tlie function of individual muscles, since, in the 
expression of melancholy ^"^ and in the typical countenance of 
thoracic and abdominal diseases,* the platysma muscle plays a 
most important part, and is therefore supplied by the nerve 
of expression. 

Again, the muscles of the region of the motUh are impor 
tant agents in the prehension of food (especially so in ani 
who often can not eat when the lips ure paralyzed), and shoi 
properly be, in some way, connected with the muscles of 
tication (chiefly supplied by the fifth nerve), and tho% of 
deglutition (supplied by the facial and the glosso-pharjTigeal 
nerves) ; hence, ,the facial nerve is afforded communicadng 
branches with l>oth the^Vt and the glos^O'pJiaryn(je€il nerves. 

One of the muscles of the fac^, the bu^ccinator^ w^hich is 
supplied exclusively by the facial nerve^ plays a most impor- 
tant part in masticatioit as well as in expression ; hence, wh 
the facial nerve is paralyzed, the cheek can no longer foi 
the food between the teeth, and a tendency toward accumul 
tion of food within the cheek of the affected side become© 

* Carpetiter, op^ €%i* 

*gir Charlra Bell« ''Anatomy of Expression." Sec, also, lutjdo hy the Riitlior, ^TU 
Human Fac« ; iu Modifications in Health and DiBeaw, etc./' ** New York Ucd. Jcmt.^ 
September, 1880. 



npor- 
mal^ 



PHYSIOLOGY OF THE FACIAL NERVE. 485 

distressing to the patient that the fingers are freqaently em- 
ployed, during attempts at mastication of the bolns^ to force 
the food between the jaws by pressure upon the external por- 
tion of the &ce/ 

The value of this muscle in expression is made manifest in 
those acts where the cheek is either inflated with air, or where 
it is drawn inward, thus indicating the states of emacia- 
tion or extreme hunger. Much of the success of a comedian 
often depends upon the control which he possesses over the 
buccinator muscle. When the/acial nerve upon both sides is 
paralyzed, mastication is almost as much impaired (on account 
of the buccinator muscles) as if the inferior maociUary nerve 
was destroyed. 

The flaccidity of the buccinator muscle in "Bell's i)araly- 
sis** accounts for the peculiar puffing mo^emevd of the cheek 
which accompanies each act of eocfpiration^ giving to the face 
an api)earance similar to that noticed when puffing of a pii)e 
is attempted ; while, in those rare cases where the facial nerve 
is paralyzed upon both sides, the face assumes a condition 
which is remarkable for the entire absence of expression, and 
which can only be compared to the effect of covering it with a 
mask. 

Many of the muscles of the face are of value as guides in 
diagnosis^ since, in certain tyi)es of disease, some parts of 
the jfece are more affected than others.' This subject, how- 
ever, is too complicated to be hastily reviewed, and it has suffi- 
cient value to merit its si)ecial consideration. 

It may be i)erceived, by reference to the diagrammatic rep- 
resentation of the branches of the facial nerve, that the tern* 
porO'facial branch animates all of the muscles of the upi)er 
part of the face, while the cermco-facial branch supplies the 
lower region of the face and portions of the neck." This ex- 
plains why, after the temporo-facial branch has been divided, 

> A. Flint, Jr., op, eit, 

' See article by the author on " The Iluman Face ; its Modifications in Health and 
Disease, and its Value as a Guide in Diagnosis : " ** New York Med. Jour.,'' December, 
1880. 

* See page 426 of this Tolame. 



436 



THE CRANIAL NERVES. 



as has ocxtirred in operations upon the cheek, the eye iftcmdt 
wide open even during sleep ; the lower lid becomes ecerUd 
fiom traction of the parts below, and also from the effect of 
gravity ; the ocGipitofrontalis and corrugator BiipercUii can 
no longer make either tmnsverse or perpendicular wrinkJ**» 
upon the forehead ; and the Tipi>er portion of the face in al>- 
nonnaUy smooth and passive, while the Itivvto- |M*rfiMH |>r>*- 
serves all its normal power of movement* 

Should the cermcO'facial branch become alone inipaireii, 
the power of prehension of food by the lii>s is arrested, the 
action of the buccinator in mastication is stopped, and that 
process is propoi-tionately interfered with ; the digastric and 
stylohyoid muscles are, however, not paraljiced, since the 
special branches to those muscles are given off alx>ve the on* 
gin of this branch, and thus deglutition is not embarrassed. 

CLIIS^ICAL POINTS AFFORDED BY THE FACIAL NERVE. 

The diseases which affect the facial nerve may produce 
the different varieties of facial spasm and paralysis / tli0 
former being the result of some lesion which creates simply 
irritation, while the latter indicates some existing pressure or 
degeneration, which impedes the free action of the nerve* 

SPASM OF THE MUSCLES OF THE PACE. 

In a class of cases, by no means infrequent^ facial spasm is 
perceived, to a greater or less degree, as the result of some 
cause of irritation to the nerve filaments of the trunk of the 
facial nerve, or to some of its bmnche^. These mimic spasms, 
or *' convulsive tic," ai*e dependent upon an hereditary ten- 
dency, in some instances; since reported cases exist where 
the second generation, and even the third, has manifested the 
symptoms of facial spasm. We also meet this condition as an 
accompaniment of epilepsy, eclampsia, hysteria, tetanus, and 
chorea ; again, in certain mental diseases, where the hmin or 
its investing membranes are affected ; and, finally, we see it 
developed under extraordinary periods of excitement. 

Cases are on record where simple exposui'e, wounds of the 



^Im 



BELUS PARALYSIS. 437 

face, and pressure upon the peripheral filaments of the facial 
nerve have resulted in facial spasm. Perhaps this condition 
is most frequently met with as an evidence of some rq/lex act^ 
excited through some other cranial nerves ; hence we find it 
associated with such causes of irritation as caries of the teeth, 
periostitis, inflammatory affections of the eyeball, lids, or con- 
junctiva. Remak reports a case where a diseased condition 
of the brachial plexus caused spasms to start in the hand and 
progress along the side of the neck to the face, again illus- 
trating the reflex character of the disease. 

It is such cases as these latter that often test the ana- 
tomical knowledge of the diagnostician, since a command of 
the various anastomoses of nerves often enables the skilled 
anatomist to detect the seat of irritation far from the apparent 
seat of disease, and thus to obviate a distressing condition by 
some simple medicinal or surgical remedy. 

The spasms of the facial muscles may assume either the 
tonic or clonic character. The former variety is observed in 
such conditions as tetanus, the late rigidity of paralyzed mus- 
cles, and the irritation following upon severe exposure and 
too intense faradization ; while the latter are the most com- 
mon, and result in those convulsive twitchings of the forehead, 
eyes, eyelids, nose, mouth, cheeks, and tongue, which pro- 
duce the most extreme and often ludicrous distortion of the 
features. I have known such clonic spasms of the face to 
be produced by the irritation of worms in the intestine in 
children, and, in one case, to follow uterine disease in an 
adult. A peculiarity of these spasms is, that certain muscles 
seem to contract in a regular sequence or rhythm, and that, 
although the contraction may be prolonged and severe, no 
fatigue is usually complained of by the patient. 

PARALYSIS OF THE MUSCLES OF THE FACE. 

The general api)earance of a sufferer from a well-marked 
attack of "Bell's paralysis" has already been depicted in a 
cut,' and described in the preceding text, under the effects 

* Sec page 427 of this volume. 



4Sd 



THE CEAJHAL XKRV^Sl 



of secrion of the facial nerve : bnt many pobits of prarrical 
V9iuB p^tain to this conditioii which have not as yet lieeo 
maptiaiied, and which help greatly in making a dia^osii^ m 
to the exciting cause and the seat of the existing lesiaii. The 
symptoms prodnced by any impairment to the free action of 
the facial neire vary to a marked extent with the degr»/ ' 
the paralysis, and the individual branches which may U 
volved ; and distinctions between the variona forms of fartal 
poralysiss met with in a large clinical field, have been devel* 
oped, by the investigations of Romlieig^ from thoae general 
propositions first advanced by BelL 

In studying the types of faetal paralysis, we may start 
with advantage by reviewing the different groups w*hich are 
clinically recognized. These may be enumemted as the ififra 
cranial ; the anditory (when? the existing lesion is confined 
to the interior parts of the temporal bone) ; the rhenmath ; 
the traumatie ; the 8i/phiUtie ; and, finally, the diphtJieritie 
form. We may also have the panilysis confined to one *^i ^' 
of the face, the unilateraL or, affecting both sides of tht^ 
face, the bilateral, or facial diplegia. 

In the intra-cranial form of facial paralysis, the lesion of 
the brain is usnally confined either to the base, or to the pons 
Varolii. If the pons Varolii is affected, the facial nerve will 
not be alone involved, as a nde, but a partial or complete 
hemiplegia will usually exists which will be on the same side 
of the body as the facial panilysis, provided the upper (an- 
terior) half of the perns is the seat of disease, but on the side 
opposite to the facial paralysis (crossed paralysis'), if the 
low^er (posterior) part of the pons is affected* There is, per- 
haps, no point in the anatomy of the encephalon which in of 
more certain value to the diagnostician than the fact, first 
pointed out by Gubler, that a line dmwn transversely across 
the pons Varolii at the points of escape of the trigemini 
marked the spot of probable decussation of fibers of the facial 
nerve ; so that, if a lesion be anterior to this line, the facial 

^ For definition of this term mud tbe TftHouB typc» met with, tlie reader to referrtd lo 
the prerioua sectioo. 



CAUSES OF BELL'S PARALYSIS 489 

paralysis will correspond to the hemiplegia, but, if behind 
thatline, the condition of "crossed paralysis'' of the facial 
and body type will be produced. A point of some diagnostic 
value in the detection of intra-cranial lesions, by means of 
the facial nerve, is aflforded by the degree of the facial paraly- 
sis, since it is usually complete if caused by lesions of the 
pons Varolii or by the pressure of tumors of the base of the 
cerebrum. 

The second form of facial paralysis, viz., that dependent 
upon some abnoTTnal condition within the temporal bone^ 
is liable to follow suppuration or haemorrhage within the 
aqueduct of Fallopius; scrofulous caries of the temporal 
bone; local d^eneration of the nerve within the aqueduct 
of Fallopius ; local pressure upon the nerve from tumors, 
etc.; and traumatisms of all kinds, of sufficient intensity to 
injure the deeper parts or to directly involve the nerve 
itself. 

If you will recall the anatomy of the facial nerve within 
the aqueduct of Fallopius, and the branches which are given 
oflP in that canal, you will be better able to appreciate the 
X)oints aflforded by this anatomical knowledge in the diag- 
nosis of the seat of a lesion which is causing facial paraly- 
sis. We have already, in connection Xvith the eflPects of 
section of the facial nerve, mentioned the facial deformity 
which ensues ; and the same description will answer for the 
eflfects of disease of the nerve, or pressure upon it, after it 
has escaped from the stylo-mastoid foramen. But the symp- 
toms to which I now propose to call your attention are not 
included in that description, since they are due to branches 
which are given oflf by the facial nerve before it escapes from 
the temporal bone ; although the same facial deformity, and 
all the evidences of impairment of the nerve on the distal 
side of the stylo-mastoid foramen, will, of necessity, be also 
present. 

If the lesion be situated above the point of origin of the 
chorda tympani, but on the distal side of the petrosal nerves, 
the sense of taste will probably be affected on the correspond- 



THE CBAmAL FEBTES. 



ing side of the anterior tw^o thirds of the tongne ; ' but the 
sense of taste is not^ as a rule, abolished, although it i« 
greatly diminished in aeuteness. How this nenre affects iIm* 
sense of taste, and the Tarious exi)eiiment8 which hare bwa 
recorded concerning it, will be found by reference to pre<?ed- 
ing pages.* 

If the lesion of the facial nerve be sitnated behind the 
ganglionic enlargement fiom which the three petrosal nenres 
arise, the patient will reveal a depression of the arch ^ the 
palate upon the affected side ; thus, it will be seen to hang 
lower than the healthy side, and to approach a straight Une 
along its free edge, mther than that of a marked curve, as in 
health. Tliis is due to the pai^alysis of the levator palati 
muscle, which is supplied \%ith motor i)Ower from MeckeFs 
ganglion, tlirough the lai^e petrosal nerve. In addition to 
this deformity, the soft palate is drawn toward the un^fect- 
ed side by the tensor palati muscle^ since the same muscle 
of the paralyzed side is no longer capal>le of acting, as it Is 
8Uj»plied by the small petrosal nerve. The distribution of the 
small petrosal nerve to the otic ganglion stiU further explains 
why, in this type of cases, the secretion of the parotid ffland 
of the affected side is diminished ; while the intimate asso- 
ciation of the chorda tjTUpani nerve vnXh. the s^uhmaxiUary 
gland accounts for deficient secretion from that source- 
It has been observed that the sen^e of hearing becomes ex- 
cessitely acute^ when the facial nerve is affected on the proxi* 
mal side of the jwiint of origin of the petrosal nen^es. This 
may possibly be due to the jmralysis of the tensor tympani 
muscle, as suggested by Landouxy, since that muscle is sup- 
plied with motor power by a filament derived from the otic 
ganglion ; although the investigations of Brown-Sequard seem 
to point to a vaso-motor spasm of the internal ear, resiiltiiig 
in a condition of hypenesthesia of the acoustic nerve. 

The third form of facial paralysis occurs in connectioii 

* Till? fpiidtT U rcf«*iTed to t1io5e po^cfl in which the guitAtorj bmnch of tb« fiflh 
nen V is dbcu^fteO, siace iuthoriiies dilfer u lo the x%\m uid isterpretatHm of tbli ^np^ 
tonu 

' See p«ge 406 of thU rotum^. 



CAUSES OF BELVS PARALYSIS. 441 

with the rheumaiic diathesis. It is well known that the in- 
fluence of cold, which is paxticularly liable to favor rheu- 
matic manifestations, is more keenly felt in the region of the 
cheek and eyelids, as shown by Weber ; and the experiments 
of Wachsmuth,' upon the effect of cold upon the vaso-motor 
fibers in the region of the stylo-mastoid foramen, also point 
to the retardation, or, possibly, the entire suppression, of the 
blood supply to the facial nerve, as the explanation of this 
type of paralysis. A mild form of periostitis in the bony 
canals, tlirough which the different branches of the facial 
nerve pass, may also occur in the rheumatic type as an excit- 
ing cause. 

The traumatic types of facial paralysis may involve the 
entire nerve or only individual branches. Its symptoms, 
therefore, somewhat depend upon the situation and extent of 
the injury. It has been known to follow severe contusions of 
the face, cheek, or neck, incisions made by the surgeon, saber 
cuts and gunshot wounds, the compression exerted by the 
forceps during delivery, the pressure of growing tumors, sup- 
puration within the parotid gland or lymphatics of that 
region,^ and the pressure caused by extensive or deep cica- 
trices. This type of paralysis is often extremely obstinate 
and of long duration, and may be permanent ; since the nerve 
may have undergone changes in its structure or the muscles 
may have become impaired. 

In syphilis^ facial paralysis is sometimes developed. It 
may thus indicate the formation of intra-cranial tumors or 
meningeal exudations, which either press upon the nerve 
trunk or interfere with its fibers of origin. It may also be an 
evidence of extra-cranial lesions, such as periostitis of the 
mastoid region, tumors of the facial or cranial bones, or sup- 
puration dependent upon caries or necrosis of the temporal 
bone (if the entire nerve be affected), or of some of the facial 
bones, if individual branches only show evidences of pressure. 

Cases are on record where the symptoms of facial paraly- 
sis have followed an attack of diphtheria. This is but one of 

* As quoted by RoflenthaL 



U3 



TEE CRASZJZ 



the varicNiB forms of paralyBb whicU u^m Irequently 
as seqoete of this peculiar blood poison. 

It may be well to hastilj review the principal compliai- 
tioiu which are most frequently obeerred in coniiecticin with 
facial paralysis. These have a special importance to the sci- 
entific practitioner in enabling him to diagnose, not only rh^ 
condition of the patient, but ako the aeal of the existing 
lesion. 

We have eonsidered the effects of lesiomi within the aque- 
duct of Fallopius. These may create (in addition to tbo^e of 
the &cial muscles) symptoms referable to the impairment ol 
the chorda tympani nerve (see page 439), of the petrosal nenres 
(see page 440), acoustic manifestations, or an effect upon the 
salivary secTi?tions. 

Intracranial lesions usually cause destruction of the mo-^ 
tor power of the entire nerve, and, therefore, of all of 
branches ; hence, we are liable to have all of the pferions 
symptoms present, as well as those of facial deformity. 

Special branches of the nerve may be individually paia> 
lyzed, and thus produce symptoms referable only to tha«ie 
parts in which the motor power is deficient. The anatomy 
the separate branches, as shown in the cuts <m previo 
pages, i^ill help you to understand the special symptoiM' 
which an impairment of any one branch would produi^e. 

The condition of bilateral facial paralj/^is^ or ^^/aeial 
diphffia^'' is a rare form of disease. It implies some form of 
pressure or degeneration, which shall affect the nerve of each 
side simultaneonsly ; hence it may accomi>any a lesion situ- 
ated in the anterior half of the pons, which crosses the median 
line ; an exostosis of the interior surface of the basilar i>rocess 
of the occipital bone ; an intra-cranial aneurism ; and the pres- 
ence of excessive meningeal exudation at the base of the brain. 
It sometimes accompanies the condition of labto«g1osso-pba* 
ryngeal paralysis (Duchenne^s disease), provide<i the lesion e» 
tends so as to involve the nuclei of origin nf the farial 
and is occasionally met with in the course of certain i... ...c 

eerebral diseases. Jaccoud claims that the spoutaneous mUxhi 



:i 







CAUSES OF FACIAL DIPLEGIA. 443 

phy of both facial nerves can occur without an exciting cause 
of a local character being detected ; and the same opinion is 
maintained by Pierreson,* who found a hyperplasia of the 
connective tissue of the nerve and the development of amy- 
loid corpuscles to constitute the pathological changes. 

This type of paralysis may be due to peripheral causes, 
such as exposure to intense cold, as in sleigh-riding, rheu- 
matic inflammation of the nerves, and diseases of the petrous 
portion of the temporal bones (necrosis, caries, syphilitic 
otitis, suppurative inflammation of the middle ear, etc.). 

The exi)eriments of Schiflf ui)on animals in whom both 
facial nerves had been divided, and the investigations of Trous- 
seau, Wachsmuth,' and Davaine, have helped to clear up the 
effects of this double lesion, and to render its diagnosis from 
Duchenne's disease more positive than our previous knowl- 
edge would permit. In the human race, this condition is 
characterized by the following symptoms : a fixed and im- 
movable countenance, a peculiar drooping of the angles of the 
mouth, a collapsed appearance of the nostrils during inspira- 
tion, a sinking inward of the cheeks during the inspiratory 
effort, and a protrusion or inflation of the cheek when the air 
is expired. The tone of the voice becomes of the most dis- 
tinctly nasal quality, and the patient, from the inability to 
pronounce the labial consonants, is almost unable to make the 
simplest sentences intelligible. In consequence of paralysis 
of the buccinator muscles, which are supplied by the facial 
nerves, the act of mastication becomes embarrassed, and de- 
glutition is greatly interfered with ; hence it is not uncom- 
mon to see such patients use the finger to push the food into 
the grasp of the isthmus of the fauces, so as to swallow the 
bolus. When the head is inclined forward, the saliva runs 
from the mouth, in spite of all efforts to prevent it. The con- 
dition of the eyes," which remain wide open on account of the 

* As quoted by Rosenthal. 

* As quoted by Hammond. 

* In both the unUatcral and bilateral forms of facial paralyflis, the patient often can 
ATold the irritation of dirt and the intense lijrht by closing the eyelids with the preaauro 
of ibt finger, or by a atrip of adhesive plaster. 



444 



THE CRAmAL NERVES, 



paralysis of the orbicularis palpebrarum muscles, affor 
most important point in the discrimination between this 
ease and the pamlysis of Duchenne. So marked \b llm 
formity that tlie patient cau not wink, and thus the tears are 
not distributed over the globe of the eye, to wash off any dust 
which may enter ; while, on account of the paralysis of the 
tensor tarsi muscle, the tears are not drawn into the lachry* 
mal sac, and therefore tend to flow over the cheek and create 
scalding, 

THE AUDITORY, OR EIGHTO NERVE. 

This nerve is strictly one of special sense^ namely^ that i 
Jiearing. It arises chiefly from a gray nucleus in the floor 
of the fourth ventricle (where its fibers form the so-called 

8 



23: 



Fio. 119. — A diagram of the auditory ntnrvc and ita hranehm, 

1, mtdiiQrv n«rve^ entering the mtaiwt audiioritu intrmuM ; 2, oommtinicating filuncntl 1 

the faricd fiert^e, given off in the inUmal auditory mnat ; 8, fiUments givoi off to 
supply the eochtm ; 4, filaments giren off to supply the postrHcr afmicireuiar eanrnt; 
G, flUmentii given off to iuppty the taectdf ; 6, (llari n off to supply Ike mir^ 

de ; Ij fil&mcDt8 given off to supply the txitrna/ it eanal : «J^ filaJtMntti 

glTcn off to supply the ampuilxK o/tJit superior scmH<fi^<ur CTtnd/. 

''line«e tranaversse" which decussate in the median line), and 
also^ in part, from three other nuclei of the medulla oblon- 
gata (page 2(57), Some of its fibers may be also traced to the 
Jlocculus and the nucleus /astigii and nucleiis dent^ius of 
the cerebellum. From recent statements of Lockhart Clarfc 
additional fibers may be traced from the auditory nucl»Mii 
wliich pass directly through the restiform body of the meduU 
The course of the nerve, as fax as the orifice of the internal 




THE AUDITORY, OR EIGHTH NERVE, 



OS 



inditory cunal, lies parallel with that of the facial nerve, since 

'the same arachnoid sheath invests theni both, but, befor© 

hat canal is reached, a filament is given off from both 

aese nenes to form an interaiediate nerve^ called the *^'parH 

intermedia,'' or the *' nerve of Wrisl)erg,-' This intermediate 

jrtion is now 8iipi)08ed to be the chief source of origin of the 

Qtmda lympani nerne^ and thus {as be connected with the 

[jial Bem>e of taste. 



y' 



l-lLtJLl 



\ 

wfrmn tfie riphl nde and it »eenjrmn iU anten^in/erior part). (Sappcjr.) 

1, tmnk of the cocbkur ni*rve; 2* 2, 2, meuilirDu ' "^ ' ' ^iim; », 8» 8, 

Urniiniil t.'X|mtK<ioQ of tlio txicblonr nrrve, c>| the r<?i»0T»1 

f'f the P«uperior |iliitc of the UmlUA ipimlis; i, ^. . .i„v-,.^u uf the i 
tvttip«nl with the »ciiU reetibuli. 



The color of the audit^ji'y nerve filaments is grayish. The 
lament4? differ from those of the other cerebro-spinal nerves 
(excepting tho8e of s]>eciaJ sense) in having a softer consist- 
ence. Some of the later i^esearches seem to show that the 
filaments of this nerve are destitute of the " wlute substance 
of Schwann,'' and thus resemble those of the olfactory nervr 
while the aa^Li cylinders are of very large size as compared 
with those of other ner^^es. It 13 also clainied that small, nu- 
cleated, ganglionic enlargements q^xi be demonstrated along 
the course of these fibers of the trunk of the nerve, but the 
irilnute anatomy of the auditory nerve is yet a subject lor 
further investigation. 

Within the internal auditory caaal^ the eiirhth ner\*e 

81 



THE CRANIAL NERVES. 

divides into two branches, tlie anterior of which supplies tb** 
cochlea, while the posterior branch is distributed lo the t • 
circular canals and to the saccule and vestibuJ4f, Thi»>» 
main branches are given off close to the meatus auditoriu?* 
internus. 

At t!ie lx)ttoni of the internal auditory eanal^ the thiw 
subdivisions of the vestibular nerve pass through smnll open- 



n^ 



Fio. 117— GmfTiil viae q/ tht &rffm» 0/ kmriit^, (S«pp«7. ) 

1, pinna ; 2, c&vltj of the coodm, QO the walla of which are seen the oiiOces at t 
^reiit number of sebiceous f^aiidii ; 6, ext^miLl nuditorj m^lus; 4, angular pio^ 
Jection fonned by the iiiiion of ihe anterior portion of the concha with the posleriar 
wall of the aiiditorv canal ; &, openings of the oerumtnous g^landf^ the most iitCrTTill 
of which fonii a ctrvcd line, which coirespondf with the bc^nnin^ of the Qtmm§ 
portion of the evtemal meatus ; 6, membnuia tjnipanl and the elaatlc fibnoo* flMHK 
brane which forms fta border; 7, anterior portioa of the Incn* »^ M.*iL.n^ . n k,^ 
die of the Jnalleii> applied to the internal surfMC of the meml .1 

draws inward towani the projection of the promontory ; tO^ t> i . 

the teodoD of which is reflected at a right angle to become aiuehcd to iht* »« 
portion of the handle of the malleus; 11. trmpanic cavity ; 12, Eui*t*rh»»n fr 1 
internal or phar3m^eat cxtreroltj of which hjU been remoTed bv ii 
dicular to its curve; IH, >niperior ^midrcular canal ; 14, poolerio 
nal; 15, external semjciroular canfti ; 16, oochlett ; 17, t"-*^ — -^ - 
facial nerve ; 19, large petrosal branch, given off from r it 

of the facial and poising' below the cochlett to go to tu ^ r 

branch of the auditory nerte ; SI, ooobk^r branch of the aiiditorr nerve, 

ifigs in a cul-de-sac situated at that point, and are distributed 
to the utricle, the saccule, and the three anipullie. 

The cochlear nerve, which is the other main branch of the 
auditory, enters the ba^e of the modiolu^^ and its ftlaments 



DISTRIBUTION OF AUDITORY NERVE. 447 

subsequently escape from the central canal of the modiolus 
through minute canals^ which enable them to reach their 
I)oint of distribution in the internal portion of the cochlea. 
The terminal filaments of this nerve are now believed to be 
connected with the spindle-sTiaped cells of the organ of CortL 

It is impossible, within the compass of this lecture, to en- 
ter into the minute anatomy of the ear with sufficient detail 
to enable you to properly appreciate the mechanism by which 
the waves of sounds, produced from without, are transmitted 
to the membrana tympani, and subsequently to the cochlea, 
where they are perceived by the auditory nerve filaments. To 
properly appreciate the difficulties which arise in determining 
the exact method by which the human ear is enabled to de- 
termine not only the intensity of the sound perceived, but 
also its pitch, qtiality, and musical properties, not only 
would the anatomy have to be given in detail, but many of 
the laws of physics discussed. The following general state- 
ments, however, may assist you in studying this complicated 
subject, and afford an explanation of some of those symp- 
toms of disease which are referred to the ear. 

The diagram shown you on the blackboard ' is designed to 
assist you to grasp some of the principal points in the ana- 
tomical construction of the ear, which are necessary for the 
clear comprehension of the physiology of audition. It can be 
perceived that the external auditory canal and its accessory 
portion which we call the ear or auricle (which is placed 
on the exterior of the skull for the purpose of deflecting the 
waves of sound into that canal) lie external to the membrana 
tympani ; and, for that reason, all of these parts, viz., the 
cartilages of the pinna, its ligaments, the bcmy canal leading 
to the membrana tympani, and its cutaneous lining, are in- 
cluded under the general term " the external ear,'' in contract 
to the chambers which lie deeply within the temi)oral bone, 
called the middle ear, or " the cavity of the tympanum,'^ and 
the internal ear, or the ^^lahyrinth^ 

The middle ear, or " tympanum,'^ lies between the mem- 

' See diagnun further on in the chapter. 



THE CRANIAL NERVm 

brana tympani and the intemal ear, or '^^labyrmtlL,** and 
contained wthin the petrous portion of the temporal 
It communicates with the pharyjix^ by means of the Ei 



6 



to 



Fio. 118. — A diagram to UluMtrait the meehamUm of the act o/ketmmff. 

A, the auditor if canal (the arrow showing the wnves of iound CQlerin^) ; B, tlic i 
the middle mt\ or ^* tjfmp^nwn'^) ; C, the uiride^ oommfinleiting with the m 
hsr canals ; D^ tho $€tceuie, communicatifig with the teaU ptntifmii of the cavitj of 1 
cochlea; E, the Eustaehian tube, aUowing of the entratic« of air into th«t mi<IiUt4 
from the pharynx; 1^ the munhi^aMa tyntpam^ which first rticniresi the rifiHitlopi< 
the waves of sound ; 2^ the chain of Aon<a, which transmit thef*e vibration* to ihc I 
brane covering the fauntra otmlis (ftritiulnr li}?iiment of the stape*) ; 8, tbc i 
covering the fmaitra ovalh (annular Hgatnent of the itape*) ; 4, the /uramm 
dam^ where the waves of sound return to the cavity of the mMdle ear atid i 
(mcmbrana tympani Becundaria}; fi^ the ampul tig of the setnicfrcuUr canals ; ^1 
iiemicircul'tr atiu^n ; 7, the " xca^a rrttfibuH ** of the cochlea ; 8, ihcrupota^ at the I 
of the coohleii, where the iteala vestibuH aod the «tca1a tympani of ihc cocbk« 
each other ; 9^ the '* M/tfa fifmpani^^^ Icadia;^ downward from tlic cupola of 1h# ci 
to the foranicn rotuodum ; lo, itdermd audita f^ ouud^ where the auifttor^r 
enters. 



chian tube, and is thus enabled to aiford free access to the 
air of the external world, and insure the same density of at- 
mosphere on both sides of the membrana tympani. It fc« 
this anatomical arrangement that causes gunners to hold tl 
mouth wide open when exploding large pieces of ordnance, 
avoid a nipture of the membrana tympani, since the wares < 
sound can thus enter the Eustachian tube at the same tii 
that they pass down the external auditory canal, and the* 
membrana tymfjani should^ theoreticsiUy, be made to stand 



THE MIDDLE EAR. 449 

motionless, if the Eustachian tube were wide open, since the 
waves of sound ui)on each side of the membrane would neu- 
tralize each other.* In the cavity of the middle ear, a cTiain 
qf small hones is so arranged as to afford a source of trans- 
mission of the impulses of sound from the membrana tym- 
pani to the fenestra ovalis,' which is closed by the stapes' 




Fio. 119. — Omda of the tympanum of tfte right mde^ magmyM 4 diamden, (Arnold.) 

A, maUeus ; 1, Its head ; 2, the handle ; 8, lonp, or slender prooess ; 4, short process ; B, 
incus ; 1, Its body ; 2, tha long process with the orbicular process ; 8, short, or pos- 
terior process ; 4, articular surface recelTinfr the head of the malleus ; C, stapes ; 1, 
head ; 2, posterior cms ; 8, anterior cms ; 4, base ; C*, base of the stapes ; D, the 
three bones In their natural connection as seen from the outside ; a, malleus ; 6, 
incus ; c^ stapes. 

and its annular ligament. This chain of bones is suspend- 
ed by a ligament attached to the roof of the middle ear, and 
the sejmrate bones are connected together by joints* lined 
with synovial membranes, so that the slightest movement is 
readily carried from one to the other. Muscles are also at- 
tached to these bones, for the object of bringing the mem- 

' Valnalva's method, " which consifits of making a powerful expiration, with the mouth 
and nostrils closed," is also used if the ear be stopped with cotton at the same time. 

• A doctrine first suggested in 1851 by Edward Weber, and subsequently verified by 
experimenU in 1868 by Politzcr. 

' One of the small bones of the middle ear. 

* Helmholtz first described the exact nature of the joint between the malleus and the 
incus. He compared it to ** a joint used in certain watch-keys, where the handle can not 
be turned In one direction without carrying the steel shell with it, while in the other direct 
tion it meets with only a slight resistance.** This device assists to convert the bones hito 
a state of resistance, resembling that of a solid piece of bone, when muscular action lodu 
tUa Joint firmly. 



Hoi) 



THE CRANIAL NERVES. 



braiia tympani and the bones themselves into the heat ^possk* 
Me condition for the accurate appreciation, of soand im- 
pulses*' The cavity of tlie middle ear is in commuoieatiim 
with the cells in the mastoid portion of the temporal honf, 
and some additional effect may be thus produced upon thr 
vibrations of the air within the middle ear/ 




Fic*, 120. — The Itfi bony lahtfntith of a nr^r-bor^ tJithl, joturard and ovtwant 
jied /t*otn a pftttio^aph. (RMmger.) 

If the vride OftDAl, the bc^nnin^ of thc! spiral canal of the oochl«ft; S, tlie taflfftm 
timdA; 8, the sect^nd tum of the cocWen ; 4, the fitiftl half tum of lh« 
5, the border of the bonr wall of the ve^lilinle, stitiated betwwn the 
the seraieirculftr canaU; H, the superior, nr BJi^itiAl ^ntiicircularcntiBl ; 7, t3l«r ^ 
of the superior semictrculftr canal betit ofitwnrd ; 8, the p<i«terior, or trmntfi 
i^ mi circular c;iiial ; 0, the p'irtion of the |)Oi<terior connected wtlii the ifiip«rior 
circular canal ; 10, point of jMnction of the s'lpcrior nnd the poaterior 
crdaI ; n^ ihc ampulla 08.4ea externa; 12, the hoiixontal^ or eztcnuit 

The internal ear y or '^ lubyrlntk,^^ lies within the j)etn>u8 
portion of the temporal bone, and intenial to the tjTnpanuin, 
It consists of a series of chambers, hollowed out within the 
bone, called the nestibule^ the cochlea^ and the semieircular 

* The tcuKor tt/inpani muacle, on account of a peculiar errftngemcnt of th^ joiiil I 
tureen the miillcu,<^ and the incus, render* nU the articulationf* finn» tit^tens theliuls' Itg 
ture«s (tnd pre^i^ofl the stApcs Against the fenestra oralis, thus brining H in ooQlact i 
the rttjids of the vcitibule. Sec foot-note on page 449. 

' For the aunricAl appHeal:on of ihh arrangement, see article oq the bouM of iiif 
head, by the author, "New Yorlt Mcdit'al Record," October l(^ I81SD» 




'' 1 . utricle ; 2 

iM.i„, „. - .if Uk' ftcnt 

branotis labyTinth^'^ and is an exact pepTf>dnc'tion of the 

bony labyrinth, except that it is nmaller in point of size, so an 

[to admit the presence of tiiiid between it and the bone. It 

ffierves as a mippoftfor the tirmlnal filaments of the mtditory 

\ner(^i\ which, by b<»in^ suspended between two tlnifls^. are en- 




452 



TffE CBASIAZ yFRTKt 



abled not only to perceive the siigJiiest vibrations of iht» 
fluids/ but are also thos protected from the possibility of m* 
jury, which would be great were they placed in contact with 
the bone. The membranous labyrinth which fiUs the caTitj 
of the vestibule is divided into two jxirtions, called the saecuU 
and the utricle; the former of which commnnicates directlv 
with the cochlea, while the latter communicates with the 
semicircular canals, as can be seen in the diagram. 

The cochlea is asaentially that part of the internal Kir 
which is enabled to appreciate most of the important elemeau 
of sound, viz., its note and quaiiiy^ It comdsts of an exca- 



S.V, 



S.T. 



4Nb-^ Wmmmtr m aedhm t/tkt ^rof eoMal ofiht &Mm (i(^psnifiM/i>).> 

a T» tlM mOm wriiMi / a IL, dw f«iilii nMdu ; S. T., tlic «mAf igmffam : 1, 
irmmt «f Mttmmur: % *^m^tm •/ CMH,** oovcnnl by the '* mtmhr^mn tet^ruC 

Ihi vbolt leoph of the &p\niA ewal of the eoehleu ; 5» upper l«yi»r cif Uie tumma 
ifi/wMa omm ; 6, lower bx«<' of ike lomimt tpirtdit OMKt ; 7, • nwr^ filameat m- 
m^Hmt frooi the Mnlmif caiol 9/ ike modiohu^ ttnd (^nf to lh« myan 0/ Oorti ; t$, & 
f if yn i m ftttMbed to tlie nerte filament, odled tlie "^ginglbn tpimk." 

vation in the temporal bone which resembles, in its construe 
tion^ the shell of a snail, having a central pillar, the mndw 
luSy which runs from its base to its apex» and a spiTcd canal, 

* II It ft weU-rocQ^Dlnd law of phjsicf Uut the fluids umnsmit vihralioiis la 9ngj 
dirwCioii with equfti fort^e, aod, Iberctfore, iki better mcdiiUB ooald poislblj be bad 1 
tlie ftudilofy nenre fiUroeiito to be b contaet with. 

■ Oomplote destruction of the ioehUa pfobftblj maam total ditfniw^ wblle i 
of the aemi^rtmhr eanaU doea not Mem to have liijr mariied cffeot apoii ti» ability I 
appreciate $outid. 

' From the '' Easeotialfl of Aaatomj ^ (DarUos ud RiaBej), New Tork, ISSQ. 



00N8TBUCTI0N OF THE COCHLEA. 453 

ranning around this central i)ortion for two and a half com- 
plete turns. The spiral canal of the cochlea is divided into 
three portions called the scala mstibvMy scala tympanic and 
the scaZa medial The first communicates, at its lower part, 




Fio. 128. — Vertical tedion of the orffon of Corti of the dog^ magnified 800 diatnetcre, 

(Waldeyer.) 

a- 6, homogeneous layer of the basilar inembranc ; v, tympanic layer, with nuclei, sranii- 
lar cell protoplasm, and connective tissue ; Ou tTmpanic lip of the crista spiraUs ; e, 
thickened portion of the basilar membrane ; 4 >pinl vessel ; e, blood-vessel ; /, A, 
bundle of nerves ; ^, epithelium ; t, inner hair cell, with its basilar process, k ; /, 
head-plate of the inner pillar ; m, union of the two pillars ; n, base of the inner 
pillar ; o, base of the outer pillar ; p, 9, r, outer hair cells, with traces of the dlia ; 
t, bases of two other hair cells ; x, Hensen's prop .cell ; /-/|, lamina reticularis ; w, 
nerve fiber passing to the first hair cell, p, 

with the vestibule ; hence its name ; the second terminates in 
the middle ear, and hence its name ; while the third is, in 

' The experiments of Laborde (Dcs fonctions du lima9on, ** Trib. M^d.," Septembro 
12, 1880) to determine the function of the cochlea were made upon the Ouinea-pig, an 
animal in whom the organ is particularly accessible. The following facts were considered 
by him as fully proven : 1, Destruction of the cochlea had no effect in the production of 
vertigo or disturbances of oodrdination ; 2, destruction of the cochlea produced complete 
deafness, which, however, did not appear until several days after the operation. 

He concludes, from these facts: 1, That the auditory nerve contains both motor and 
$enm>ry fibers, the former being distributed to the eemieircufar eanaU^ the latter to the 
scKcWe, utricle, and cochlea ; 2, that the cochlea is not the only organ for the appreciation 
of sound, since the utricle and eaccule participate, to some unknown extent, in that func- 
tion ; 8, that the deafness which occurs after excision of the cochlea alone is probably 
due to an extension of inflammation to the utricle and saccule, or to the formation of a 
rigid cicatrix, which prevents the transmission of an auditory impulse to those partSL 
While these facts need subsequent confirmation (since the experiments are by no means 
ooDcluaiTe), they are worthy of due conskleration in the discussion of this complicated 
and imperfectly understood organ. 



454 



THE CRANIAL NERVES, 



reiUity, but a space partitioned off fmni rn*^ sealu v\ 
for the protection of the true organ of hearing, '"the oigan 
of Corti/' The preceding diagram (Fig, 122) will help to mak^ 
tins plain to you. 

This figure represents, in a diasi^ammatic way, the ap 
ance of a longitudinal section of the spiral cord in the coclil< 
in any portion of its two and a half turns around the modi 
lu.'i. It will be perceived at a glance that the canal is divid 
into an upi>er {s, r.) and a lower ys, t.) portion, partly l>y bn 
(6 and G) and partly by membrane (3). It will also be readil 
8m?n tliat a jK^rtion of the seala vestibuli is divided off by lh»* 
mew^rane ^ Jteissner^ and that thus a separate cavit>* is 
formed throughout the whole length of the sj^iral canal, vnWA 
the •*scala media/' Within this last-named cavity will \)e 
notictnl a Inxly covered with hair-like processes* '*the organ 
of Corti^"^ which rests upon the membrane forming the floor 
of tlio scala media, and caUed for that reason the ^' basil 





Fio, 1 2 L— The two piliar9 of iht (wyow of CortL (Sappey . ) 

A, citcmftl pillar of the organ of Corti ; 1^ body, or middle portion ; % po*tcf lor citr 
ity, or biise ; 3, cell on Its iuteruail side ; 4, ^oterior extremity ; 5, conrex »arCAC« I 
wliich it iA joined to the internal pllitir ; 5^ prolongation of thie extremity. 

II, lutoruiil pilliir of tli*? orgim of Corti : 1^ Iwxly, or middle portion ; 2, posterior «xtr«iii- 
\iy ; 3, cell on its external *>ide ; 4, unterior extreiaity ; 6, concave Nurf acw by wlddi 
It 19 joinefl til tlie external pillar; d, prolongation, lying above the corrc^poodllig 
prolongation of the external piUav. 

C, the tvro pillar? of the organ of Corti, united by their anterior extremity, and farmiD| 
An arcade, the concavity of which l<x)ka outward i 1, 1, body, or middle portiUBiOf 
the pillars ; 'i, 2, poaterior extremities ; 8, 3, oc\U attached to the posterior eslretn* 
itjcs; 4, 4, anterior extremitiea joined together; 5, lermtnal prolongoiJon of llkli 
cxir«mlty. 

memb^rane,^^ There is, furthermore, showTi in this figun? 
means by which the terminal filaments of the corhlear ner 
(one of the branches of the auditory nerve) escape from tt 
ceiUral^ canal qf ike modiolus and reach the 8CalE m€ 




^ 



Sach a figure will greatly assist you to properly appref.^iate 
the discussion of the function of eaeli oi these various parts, 
and also enable you to gi'asp the jjrincipal points in the 
physiology of the act of hearing, which sire to be con- 
sidered. 

The organ of Corti may be compared to a harj), since its 
rofts ai'e of different lengths. It is a continuous structure for 
the entii'e course of the spiml canal of the cochlea.. Helm- 
holtz has advanced the theory * that the several thousand 
stiings of this organ admit of the appi*eciation of all varieties 
of musical tone, since each note or chord creates a vibration 




I 



tar 



[, \tb,^l}%^nhuthiik 9j tkt cochimr ntrve in iftr npirnt hmitw of the coehtt^i (th« roeAJ^ 
m/rmn the riffhi tide tmd itteienjrom its antei'^in/eruxr fmrt). (Sappcf .) 

1, Inink of ttte rtH'tik'nr oetTe; 2^ 2, 2, mcinhniinous xudg of the ii|nr«i1 lattimn; 8, 8, d, 

t Inti of tlie t!f>clileiir nerve, espowtJ in it* wIimIc exti^ut by the retuovtl 

]ciU* of the lumitm spinilk; 4^ orifice* vf coTnttiuntcadon of the ac«U 

|ytu{)uiu Willi uic i^caU Vi'J^tibuU. 

in those strings only which are necessary to reproduce it^ in 
the same way as a piano, when a note is sounded, will create 
a vibration in the same string of an adjoining instruuient. 
Hensen, however, claims that the basilar membrane is com- 
posed of elastic fibers of varying f^ngfhs,* and that these 
tmrate fibei-s are thrown into vibration by sounds carried to 
he cochlea, w^hich, in turn, transmit their vibration to the 



* Thtt ihecrry In opposed by the fwds ibat the nxU of OortI uv mot datfk, and tlioy 
mr« d&imi *p Hrdu^ who enn unque«tioaAhly prroe-lvc ^MiuL 

* tu %r. HJtboin this theory U aitiibutcd to Ildmholt& 




45Q 



ra» CRANIAL KEnVES. 



organ of Corti lying n\)on them, and thus inform the anditur; 
nerve tilaments of the effect. of each individnal sound.' 

In the act of hearing, the vibrations produced within the 
menibrana tympani by the waves of sound are tniiismitled 
across the cavity of the middle ear, to a membrane eoveiiiur 
an opening nearly opposite the external dmm^ culled ihf 
fenestra ovalis^ by means of a chain of small boneji within 
the cavity of the middle ear, and, by means of secondary 
vibrations thus produced within this latter membrane^ the 
impulse is transmitted to the fluids qf the vestibule , Tht? 
vibrations now travel along the fluids of the scala vestibuli a( 
the cochlea and of the semicircular canals, thna passtng ia 
two different directions* In the semicircular canals^ 
ing to some observers, the direction from which the 
springs is perceived,' while the vibrations carried 
the scala media ' in the cochlea are transmitted to the fib- 
raents of the auditory nerve in the " ox^gan of Corti, ** prol 
bly by means of vibrations of the membrana hasilaris^ thii 
affording the appreciation of the note and the quality of 
the sound perceived. After reaching the apex of the coch- 
lea, the vibrations are transmitted from the scala vestibuli 
downward along the course of the scala tympani till thi 
reach the *' membrana tympani secundaria,'* which cove 
t\i^ fenestra TotuTida,* v^h^ve they are lost/ being no loi 



* The memhrana tedoria^ or ** mmihrang cf CorHy^* probably ftcU M m 
srrest the ribrtitioiis excited vriihin the ecnlm oiedia^ u its aitustloD Bugg«*ls no otlvr fM** 
Bible futiction. 

* The fuDction of the scmidrciiUr cdDtlB is yet ii matter of doubt, and i« nmr i 
ing the attention of experimental physiologista. They are snppos^d by fionie itjtliiif* J 
reljeTc exoessnV pretsure within the labyrinth when the stapes is driven too fordhly in- 
ward ; and, by others, to txreU tkt Jiuui of tht: lah^trintk ; while by some they are * 
ered to be Uie external organs of coordination of muscular movement. 

* The saccule cooimanicato^ with the scala media by mcana of a email eatiAl (d 
in ¥\p 121), called the **cana1te rennicn«," 

* An opening In the inner wall of the cavity of the middle car. 

* According to aome authorities the vibrations in the membrmtui tjiDpinl iK^umtaria 
are created, t!muUaneou«Iy with those at the fenestra ovalU, by Ibe ffbratlaiia of tlw 
air tn the middle car created by the movements of the external drain menibr»n«, «imI 
an impulse thuii travels <)imultaneously along the scala tytnpanl and tbe loala ToitllHilI, 
both [pinff in the tame tiirfttion^ to meet each other at the ei^»Ua, Tbey coniidT tlM tteaH't 
drum, at Ihc foramen rotundum, aa a proof of thiii function, but It muit lie ipfMiiBl tofl^f 
one that all the openings of the labyrinth intu the middle car mutft be closed la mamm m^ 



PHYSIOLOQ 7 OF A UDITION. 457 

transmitted, on account of the absence of any conducting 
medium. 

The free entrance of air to the cavity of the tympanum, 
or the middle ear, affords an equal density of 'air Mpon either 
side of the meTribrana tympanic and thus insures a vibration 
of that membrane in absolute imison with the vibrations of 
the sound which it is called upon to record, as the waves pass 
down the external auditory canal. 

The function of the organ of Cdrti^ of the membrana bast- 
lariSj or of the otoliths, can not be stated with any degree of 
certainty, since new discoveries are constantly being made, 
although some theories of their functions have been already 
given. 

The minute construction of the scala media and its con- 
tained organs can be found by reference to more extensive 
treatises. 

CLIiriCAL POIKTS OF INTBBEST DEPENDENT UPON TEE AUDrrOBY 

NERVE. 

In attacks of auditory vertigo, or Meniere's disease, there 
is much more than ordinary giddiness. The patient will often 

to prevent the etagfe of ihe perilympk. While U is cUfflealt to podtlrdy decide this point. 
I am personally incllnad to regard the foramen rotundom as ^% mat of Urmination of 
wave sounds, rather than a means of tramniiuion of trnpuUm to the flnids of the oochlea. 
Dr. A. H. Bud(, in a late tueatise on the ** Diagnosis and Treatment of Ear Diseases/' 
again advocates theories long maintained by him as to the physiology of audition, which 
may be thus given : The impulse of tho stapes, at the fenestra ovaKs, is carried by means 
of the periiymph directly into the scala vestibuli. This causes compression of the fluid in 
tho scala media, which, in turn, causes pressure upon and movement of the elastic ** mem- 
brana basilaris." The pressure is thus transmitted, for a second time, to the fluid in the 
9eala tympatdy and, as fluids are incompressible, the membrana tympani secundaria, which 
doses tho foramen rotundum, is forced tnfo the eavUy of the middle ear until the force 
is expended, when it returns to its normal condition. It will be thus perceived that he 
discards the ioceufe and the eana'is reunions as a channel for the passage of the acoustic 
wave. He also questions the existence of any communication, at the cupola^ between the 
scala vestibuli and the scala tympani. While his theory seems ingenious, and perhaps 
more in aooordsnce with fact than the older views, and is well illustrated by diagrams 
and supported by some carefully conducted experiments, still it can not, as yet, be said 
to be positively oonfirmed. His view as to the absurdity of the membrana tympani w- 
tmndaria being a transmitter of eound waves to the cochlea agrees with my own, as advo- 
cated above. He seems also to favor the theory that the basilar membrane \^ the true 
mbrmting madiiim, which carries to the auditory nerve the appreciation of the note 
aoonded, rather than the " oigan of CortL*' 



458 



TEE CRANIAL NERVES, 



tell you that, when the attack commenced, everything be^ran 
to whirl, or possibly appeared to be moving toward one ^i*l*^ 
that his gait became unsteady, and, if walking was pcxssi : 
that he reeled and staggered ; while, in some severe casee^ th*" 
patient feels unsafe even when lying upon a bed or sofa^ aod 
may be obliged to grasp the sides of the couch to protect him- 



FlQ. 1 26.^ — ki^kt memhvana tympanl^ tctok from \oitldn, Fj^OfH a p?mi4>p^afih^ m 

reduced. (Radio^er) 

1, head of the malleuR, divided ; 2, nock of tlie malleus ; 8, htndle of the nuilleiui, 
the tendon of the tensor eympanl niii«cle ; 4+ divide i tendon of the tetu^or tymp 
B, 6, portion of the malkuH between the layers of the membrftna tfmpanr ; t, c 
(radiating) and inner (circular) fibet* of the roembrana tymimni ; H, fibrous nag 
the metnbrana tjinpani ; 9, H, IB, doiitated fibers, discovered by Grubcr; HX, jw* 
nor pocket; 11, connection of the posterior pocket with the malleus; 12, aa.Wrl 
pocket; 13^ chorda tympam nerve. 

self from a sensation of falling. In many cases, these Eym 
toms are markedly intensified by movement qf the head^ and» 
in some instances, such movements often tend to bring abont 
an attack.* The patient is usnidly pale and liaf;gard, some- 

' Btuoard, ** Lancet," March i IsTti 




MENIERE'S DISEASE. 459 

times perspires freely, and often vomits/ while ^am within 
the head is a symptom which not infrequently accompanies 
such an attack. The extent to which this type of vertigo 
may be manifested varies from an attack of but momentary 
duration, where the patient can retain his feet, to those severe 
forms of the disease where the attack is accompanied by a 
loss of consciousness, which may remain for some hours, and 
resemble the condition of epileptic vertigo. 

There seems to be little doubt that, in these cases, the at- 
tack is always preceded or followed by some abnormal con- 
dition of the ear, and that this diseased condition was the 
starting point of the vertigo.' Sometimes the patient has 
long been deaf in one ear, or a condition of deafness may 
follow the first attack of tertigo ; again, the approach of an 
attack of vertigo may be told by the occurrence of noises 
within the ear of one side, while, in some cases, there exists 
a constant noise within the ear, which increases as the attack 
of vertigo is imminent. 

It is often extremely diflBicult to persuade a patient, suffer- 
ing from this affection, that the attack is not dependent upon 
a disordered state of the digestive apparatus^ and especially is 
this the case when the ear trouble is of old standing, or when 
the x>atient is unconscious of any defect in his hearing, which 
is by no means an unusual occurrence. Such patients are 
better satisfied if the attack be attributed to the liver, dys- 
I)epsia, or nervousness. I quote the following sentence from 
Hughlings- Jackson ' as evidence that this difficulty is met 
with even among the most enlightened of the community. 
He says : '' Even medical men, who have aural disease, often 
totally reject the proffered explanation of their attacks of 
vertigo ; many of them ascribe their ailment to digestive 

» Ferrier, ** Vomiting in connection with cerebral disoaae," " Brain," July, 1870. 

* The occurrence of vertigo and interference with coordination i8 not alone produced 
by local disease of the ear, even when assodated with impairment of hearing. It may 
indicate disease of the cerebellum or of the medulla oblongata, which creates irritation of 
or some interference with the auditory nucleus. For the clinical facts pertaining to this 
symptom, the reader is referred to previous pages of this volume. 

* Hoghlings-Jackson, "I^ancet," March 11, 1876; same author, "Lancet," March 11, 
1876; Oowers, " Lancet,'' March, October, 1880. 




Fig. 127. — Scriiofi of the ^rut turn of tfu^ Hfnrat cemai of a mi nemljfJiom^^Sttiiom ^f lli 
totMea of a human /trivts at tke foutih monik. F)riom aplyiogn^th, amd MMlM 
reduced.* (Rudinger) 

Upper figure: 1, 2, 6, lamina ftpiralin; 2^ lower plate; ^, 4, A^ 5, nenrtu cncftiU 
membrane of Hois^ncr ; 8, mcmbniEia t^ctoria ; 9, epitheliiira ; 10^ 1 1, pUUnK 
12, inner hair cells ; 1*% outer hair cella; 14, 16, mcfnbrtiia ba«i)arii; Ifl, ffift!] 
liuin in the sulcus spiralis; 17, 18, 19, U^ftineatum epirale ; SO, epltal cioal bek 
the membrana basilarin. 

L^wer figurt? : S T, S T, 5, 6, 7, 7, B, 8, ncala tympmni ; S V, S V, 9, 9. acda riwUbiili : ! 
bA«e of the cochlea ; 2, apex ; 3, 4, oentnU cotmnn ; 10, 10, 10, 10, ductu'^ 
1 1, briiuehtiii (»f the ncrrus cochlearis ; 12, 1 %^ 1 2, apiml gnngUon ; IH, 14. 
mv apinilis ; Ifi, membrane of tleisaner ; 16, epitbeUum ; 1 7, outer Kntr . , 
thcliitm of the membraua ba^ikris ; 19, nervou* (ylnmcnts ; ti\ uninn 
ba^iilaHs with the lipimentum Apirnle ; 21, epithelium of the perii 
<lticttH cochteam ; 22, 33, membrane tectoria ; S4, apirml canal below iIm i 
basilaria. 




FUNCTION OF SEMICIRCULAR CANALS, 401 

den, he had a jyain in his head, was very giddy, fell in the 
shrubs, and vomited. This was plainly ear vertigo, as he 
himself knew. But he had the following diagnoses made of 
his case by other medical men : 1, nothing ; 2, nervousness ; 
3, deranged stomach." 

That some persons who are deaf in one ear are absolutely 
unconscious of it is too often noticed to be now disputed. 
Gowers * lays stress upon this point in the following words : 
"The fact that the patient may be unconscious of a most sig- 
nificant auditory defect lessens the value of f onner observa- 
tions as evidence of the definite character of stomachal ver- 
tigo. My own conviction is that, in the vast majority of 
cases in which a vertigo of definite and uniform character is 
apparently excited by gastric disturbance, an auditory defect 
will be discovered on careful examination." 

Patients Hfflicted with diseases of the ear may, in some 
cases, make themselves dizzy by pressure upon the ear of the 
affected side ; * while oscillatory movements of the eyes may 
occasionally accompany the vertigo dependent upon disease 
of the acoustic apparatus. 

It is well known that the semicircular canals within the 
temix)ral bone, when diseased, are liable to create the so-called 
Meniere's malady, in which constant vertigo is a prominent 
symptom ; and experiments upon birds and animals • seem to 
show that, in some unknown way, these canals affect coordi- 
nation of movement and tend to preserve the equilibrium of 
the body. 

When the horizontal canal of the bird is cut, the head is 
constantly moved from side to side ; when the posterior rerti- 
cal canal is cut, the head is moved up and down ; when the 
anterior vertical canal is severed, the movement of the head 
is in a diagonal direcition. If section of either of these canals 
be made, upcm both sides of the head, the movements of the 
head above described are permanent ; but, if made on one 

• "Brit. Med. Jour.," April, 18V7. 

* Schwaback, as quoted by niighlingp^ackson. 

*Flourens, 1824; Crum Brown, **Jour. Anat. Pbys.," 1874; Cyon, "Thdse pour le 
doetormt in medicine,*' as quoted by Foster. 



402 



THE CRANIAL NERVES. 



side only, they tend to dissipi>ejir within twenty-f i lur or ' 
eight horn's/ K the same class of experiments be made upon 
mbbits, the movements of the head are less marked, but osdl* 
lating mov ements of the eyeballs (nystagmus) are developed : 
while, if made upon eertam other animals, a loss of eoordim 
tion in the movements of the body and limbs is fiometime^ 
produced.' 

When a person is rotated for some time, a sense of rert%o 
is produced ; and tliis symptom seems to warrant the supimeri* 
tion that some abnormal effect \b produced within the ^emidr- 
mdar vanalH^ through the auditory nerve filaments, possiblf 
as a result of concussion of the fluids of ths ear agaiiijst the 
bony wall,* 

The following quotation from Michael Foster,* in dis€ti»^ 
ing the different theories advanced to explain coordination of 
movement and the various reflex phenomena which are con- 
stantly brouglit to the notice of the physiologist, seems 
ticularly applicable to the practical branches of mecliciiid 
''All day long, and every day, multitudinous afferent im- 
pulses, from eye and ear, and skin and muscle, and other 
tissues and organs, are streaming into our nervous sjrstemt 
and, did each afferent impulse produce its cori'elative motor 
impulse, our life would be a prolonged convulsion. Aa it is, 



* E. Cyon, rt;>. rt/., 1878, 

* Tbe cxperimciits of Arthur Boucher^ made in 1S73, eeem U> conflict wHh 
Cyon, Golt?, and FIoureni%, aa to the function of the fiemidrcukr cahaIs. He i 
the section of either ciliuiI can be made without cau^sing any symptomf of inockdnliaatiflB* 
provided the audiiory nert*€ filamenh an not piiHcd upon. The fact thttt Um* nvilHorj 
norve U not bound down at anj point between the brain and the labyrinth 4M[pUiB% i 
cording to thU ob^cTver, why tbe tiightest traftion upon tt may injure its attm-hnMnt&l 
the medulla, and thus create the symptoms dcscritied by Cjon, GoUi, and Floureoi. 

' A. 11. Buck I In a late treatise, reiterates his former statement, that n«im9> vre ] 
found in the »emieireu1ar canals, except in the ampoIlsD. This fact be addnoM ia 
port ol the theory that they have no relation to the perception of sound inipul«c«. Ifo 
a1«o claimi} that the small size of this portion of the membranous labyrmth, as oimpttrt^ 
with the <liameter of the bony excaTation^ coupled with the peculiar reticu1at#«l ama^ 
inenl which exists in the apaoe between the membranous tube and the hoxxy watt, fur 
BUStains his objection. This author seems to claim that the semicircular eauaU a*-t i 
means of relief to extreme intra-cochleai' pressure. Certainly, martt U^t ia Hfcdtd i 
the const ruction of this portion of tbe iniemal ear, before Iti fiiiio|ioit cut l»a | 
determined, 

* Op. dt. 



FUNCTION OF TEE TYMPANIC MUSCLES. 463 

by the checks and counter-checks of cerebral and spinal activ- 
ities, all these impulses are drilled and marshaled, and kept 
in hand, in orderly array, till a movement is called for ; and 
thus we are able to execute at will the most complex bodily 
manceuvres, knowing only why^ and unconscious, or but dimly 
conscious, how we carry them out." 

The tensor tympani muscle^ which has previously been 
mentioned as deriving its motor power from the fifth nerve 
and otic ganglion, is of use, even in the quiescent state, in 
preventing the membrana tympani from being pushed too far 
' outward. During its contraction, the membranous drum of 
the ear is made tense, for the puri)ose of deadening some 
sounds or of favoring the reception of others, by bringing the 
tension of the membrane in more perfect attune to the sounds 
which fall upon it. It may, therefore, be considered in some 
respects as an analogue to the ciliary muscle of the eye, 
since both act as a sort of accommodation to a mechanism. 
In some persons, this muscle is under voluntary control, and 
thus a crackling sound may be produced within the ear at 
will, or discords be produced when musical sounds are being 
listened to. 

The stapedius muscle^ which derives its motor power from 
the facial nerve, is supposed to regulate the movements of the 
stapes (one of the small bones of the middle ear), and esi)e- 
cially to prevent any sudden or excessive movement of the 
membrana tympani from forcing its base too far into the 
fenestra ovalis. 

The Eusta/ihian tube is unquestionably open during the 
act qf swallowing^ but it is still disputed whether it remains 
permanently open or is open at intervals. The swelling of 
the mucous membrane which lines the tube, in catarrhal 
inflammation, interferes with the entrance of air into the 
middle ear, and is frequently associated with that peculiar 
ringing or buzzing in the ear so often present during attacks 
of influenza. One of the functions of this tube is undoubtedly 
to afford a means of exit for the secretions of the cavity of 
the middle ear, and, in case of inflammation of that cavity. 



464 THE CRANIAL NER VE8. 

should the Eustachain tnbe become closed, perforation (fth 
drum will ensue, when the presence of the accmnulated pns 
creates imperfect nutrition of that membrane and consequent 
ulceration of its coats. 

Waves of sound can and do reach the endolymph of the 
internal ear by direct condiLction through the skull. Since, 
however, sonorous vibrations are transmitted from the air to 
solids and liquids (and most sounds come to us through the 
air), some special apparatus is required to thus transfer the 
aerial vibrations to the fluids of the labyrinth. The late me- 
chanical devices, recommended for the relief of perfect deaf- 
ness, in which the teeth are used as a conducting medium, 
have not as yet fulfilled the predictions of their inventors.* 

The deafness which often follows suppuration of the mid- 
dle ear does not necessarily indicate any diseased condition 
of the auditory nerve, since it may be the result of perfora- 
tion of the membraua tympani* or of an abnormal condition 
of the hones of the middle ear^ both of which might interfere 
most seriously with the transmission of sound. 

Foreign bodies in the ear often create most alarm in(f 
syviptoms ; and even an accumulation of wax, pressing on the 
drum, may create a mental condition strongly resembling the 
excitement of alcohol or mania.* Even syringing the ear has 
been known to produce fainting and severe attack of audi- 
tory vertigo. Prolonged suppuration of the middle ear may 
be the direct cause of fatal inflammation of the meninges of 
the brain. 

Neuroses of the acoustic nerve are, of necessity, more ob- 
scure and difficult of detection than those of the other special 

* It has long been the custom with otologists to use a tuning-fork, placed upon the 
forehead (when in vibration), to determine between disease of the middle car and that of 
the labyrinth ; since in the former the affected ear hears the tuning-fork most plainly, 
while, in the latter, the unaffected ear hears it most distinctly. 

' Perforation of the cxUrnal drum of the ear does not necessarily create deafness*. 
That remarkable case, reported by Sir Astley Cooper, when both drums were nearly de- 
stroyed and where the patient could still hear ordinary conversation, illustrates thia 
point. 

* See case of a louse in the ear, reported by Hughlings Jackson, " Lancet," Octi»ber, 
1880. 



NEUROSES OF THE AUDITORY NERVE. 465 

senses ; since the tests of normal sight, smell, and taste are 
much more easy and satisfactory than the appreciation of the 
faculty of a fine discrimination on the part of the patient be- 
tween notes of a diflferent pitch and quality. To what extent 
the original and exhaustive researches of Brenner,* as to the 
value of the galvanic current in the diagnosis of abnormal con- 
ditions of the nerve filaments within the chambers of the laby- 
rinth, will be sustained by pathological and clinical investiga- 
tion, it is difficult now to say ; but it certainly appears to shed 
some light upon a field of diagnosis which has been almost 
unexplored on account of the difficulties which have hitherto 
existed. It will exceed the scope of this volume to enter into 
the detail of this new method, since the principles of the 
manifestation of the electric current upon nerve tissue would 
have to be explained, and the diflferent formulae of nerve reac- 
tion given. It can, however, be stated that the principle con- 
sists of obtaining certain sensations by means of the auditory- 
nerve filaments, when one moistened pole of an electric bat- 
tery is placed upon the tragus or the auditory meatus, and 
the other to the back of the neck or the inner side of the 
arm, and the intensity of the current regulated by means of 
the rheostat.' By this means the condition of acoustic hyper- 
esthesia and of anaesthesia may be detected with an accuracy 
which older methods could not aflford. 

The state of acoustic hypercBsthesia may be of central 
origin or dei)endent upon some peripheral cause. If due to 
the former, it may be developed in connection with chronic 
cephalalgia, hysteria, insanity, cerebral hyi)er«emia, and with 
irritative conditions of the brain or spinal cord. It is some- 
times associated with hallucinations of hearing, esi)ecially 
if present as a complication of insanity. The peripheral 
causes of this condition comprise anything which can pro- 
duce an exaggeratixm of the tension of the tnuscles or bones 
of the middle ear, thus resulting in a constant compression 
of the internal structures of the labyrinth. The -experi- 
ments of Lucae seem to point to the tensor tympani mus- 

I As disoiiaied in detail by Erb, Rosenthal, and others. ' Erb*B rule. 



4M TSi: CXAJZAL XBMVB& 

<it ^& -flat ±ffm:i zi Kciat^edaniig die bones of the middk 
40? z: iat» ^rtKzecc KCKcnska of mMuieal tones, while the 
itsp^^i^ 'L4 V, 't^ri^ zr*^^£=!S 'r-Tier ibe J^commodation for shriller 
ajbi %•;■%-« %^..'-:J s^'t^^-i^ itmtaiiims. We can thus' under- 
jGUfi. if T2L^ rtf- zrx^ Jk-if paialTsis of the stai>edias mnflcle 
w-cji KTiAZr- :kx lTT ^r ji .^dii »ji m of ifae acoustic apj^aratus, and 
ft» !ifii« Bi2$ifii^ 3fiiT be- ^^?ctied in fMisl paralysis, how all of 
the c&ss^s K'i zhi^z c\^atSA?ik bbt be the eaccdtiiig causes also 
of thi$ a^ieifcs:^ c-f i&e mr.^ 

Tile ^saK- of 'JA^4tAiffia of the aadit<ny nefrve is always 
assxia;^ viih <oiifee <iereie and persistent defect in hearing, 
sincv' the fiiaaten:? of the anditorr nerre are no longer able to 
tnnsadt the impi>?!Sta<tts of sonnd. Its causes are bnt pooily 
and^stwdL bat it ^leems positnre that leaimis of the postericnr 
rmoifes itf the me!Scv<ephakHu the mednllay and cerebellam, as 
v«ll as new gxvkwths at the base of the brain, ezoessiye intra- 
cranial pKs$ni>^. and local disease of the labyrinth itself, may 
be thus manifested. The deafness which follows the exan- 
thnaatoos fevers^ and is obsenred in hysteria and ataxia, 
usuallT indicates changes in the meninges of the brain, which, 
if ^veiv, pixxluce an incurable loss of hearing. Malforma- 
tions of the interoal or middle ear, either congenital, or ac- 
quiivil durinir childhood after cerebral diseases, are the com- 
mon causes of <Ua/'mutism. 

TEE GLOSSO-PHARYNGEAL, OR NINTH NERVE. 

Like the two previous nerves, both the superficial and 
deep points of origin of the glosso-pharyngeal nerve are situ- 
ated in the medulla oblongata, a separate ffray nucleus in the 
floor of tlie fourth rentride being ascribed to it.* This nerve 
escaj^es from a groove between the lateral tract and the reBti- 
form body of the medulla, lying below the auditory nerve 
and above the pneumogastric, and passes out of the cavity of 

> This may be deemed incompatible with statements made on page 440 of this toI- 
ume, as the tensor tympani muscle was there stated to be an agent in creating auditory 
defect in BelPs paralysis. 

' See previous page in this section, in whidi its deep origin is discuased. 



THB QLOSSO-PHABYNQEAL, OR Nl^TH NBRVK 407 

the cninium by the jugular foramen, where it lies in close 
relation with the pneumogastric and spinal accessory nerves, 
the jugular vein, and tlin inferior meningeal artery. It pos- 
sesses *motor and sensory fibers, and fibers which assist in 
the appreciation of the special sense of taste. 



20^ 



^^^ 



17 Ji 



^1^ 



1 1, Uf'-" ^"^'* '^' *^** fif**^ ^^t^vn : 9 .*"ncriu,T^ of c;ajBper ; 8, f>pht1iiitm!c tlivi(«ion of the flfih ; 

lior tnattllnry diYiBion ; 6, 10, /in<7ua/ branch 

'J tht chorda t^fmpani ; 7» branch from the »ub- 

MuguM-i to the tinirtini bmtali uf the fifth ; 8, eharda iiftnpani ; 9, inferior dental 

ll«nr«; 10^ lervittiml (iUiii<fnt« of Mio lingtial tic-rve ; U» «ubrutii ill itry ganglion ; 12, 

jnjlo^bToid branch of (he in ntnl m^rrc ; IS, interior M\y of tbt* digftttHc 

ile; 14, BcctloQ of tho I rnuBcle; 10, V&^ ohmihpharjffufmi nn't** ; 16« 

o/ Andtfteh, H, ^rtinmr^ from tha glma<h§JMrjfn^«al to (kr Hffffo-^fouiu 

tk0 J^o^wlktuymffgm rnimlm : 19, 19, pnoanopstflo; tU, 21, ^nglia of the 

jirtrfo; 8a» W ■ ' 

•ubliagual nerve aiut brmnche^, 



rfntQinoif^rte ; %% SS, iUfM*rlor larvngcd iterrn; S3, iif»I&al acoesoorv : Jl. ifn 26, 
S7, «8, tublii 



By reference to the diagram/ it wU be perceived that two 
[panglioform enlargements are developed upon this nerve^ the 
upper one being situated on a level of the upper opening of 

' 8m Fig. Ii9, on the followbi]^ pigjQ. 



4^ 



THE CRAKIAL NERVES. 



the jugular forameiL 




Fig. 12y. — A dinqram of tfu hrancha of 
tlw ninth cniuial or piatso-pharyn- 
p€al mri't. 



1. filaments of oriirin, extending into 
the nietiulla oblongata; 2, xhejup. 
ular foranun^ throus^h which the 
nervf escape-^ from the cranium ; 
8, tlie jurruhir aoupliun^ developed 
uj>on tiie nerve in \\\q juffulnr fora- 
men : 4, the fj'tnpHon of Andtrttch^ 
or the " /)eirouj< tjannhon "/ 5, the 
auricular branchy derivinir a fila- 
ment also from the pneiimo^stric 
ner\'e ; G, a eommunicatiufj branch 
to the pnctunofjastnc nerve ; 7, a 
conwiunictitlnff branch to the sym- 
pathetic nerve ; 8, the tymp^iuie 
branch or " Jac^jbson\H «mr,'' dis- 
tributed to the middle ear; i\ a 
communicatiuff branch to the carot- 
id plexus of the sympathetic ; 10, 
the tonsillar branches^ distributed 
to the tonsil ; 11, a portion of the 
pharyngotl />/rxws, formed also by 
the pneumojrastric nerve; 12, the 
lingual branching distributed to the 
mucous membrane and the papillaj 
of the base and sides of the tongue. 



hfle the lower one lies slightly below the 
foramen. To the first, the name 
*'^juffidar ganglion " is ap- 
plied, while the second is callefl 
the ''^ganglion qf Andersch^ 
after its discoverer. These two 
ganglia do not include the same 
relative proportionof nerve fibers 
derived from theglosso-phaiyn- 
geal, since the jngnlar ganglion 
is developed upon only a por- 
tion of the nerve, while the 
ganglion of Andersch includes 
all the filaments of the trunk of 
that nerve. 

Within the jugular foramen, 
the glosso-pharyngeal nerve lies 
in front of the spinal accessory 
and pneumogastric nerves, which 
are separated from it by a sheath 
which invests the two latter, and 
it bears an intimate relation with 
the jugular vein within the fora- 
men, and also in the neck. 

As a motor nerve^^ the glosso- 
pharyngeal supplies the levator 
palati, azygos uvulae,* stylo- 
pharyngeus, and the middle 
constrictor of the pharj^nx; 
while, as a nerve of general sen- 



' It is extreiDely doubtful if the glosso- 
pharyngeal nerre possesses any motor fibers 
which are not derived from other nervt* by 
filaments of communication. 

* These muscles, if supplied by this nerve 
(as experiments seem to show), are reached 
by fibers sent to the facial nerve, and after 
ward, by means of the great petrosal branch, 
to Meckel's ganglion. 




DISTRIBUTION OF GLOSSO-PnARYNGEAL NERVE, 



isation^ it supplies the root of the tongue, the soft palate, the 
pharynx, the Enstachian tube, and the tjTnpaniim. It will be 
thus perceived that the glossopharyngeal nerve possesses, 




Fro. 1S0,_/\tpt//tf of the ionput, (Sdppey.) 

1, 1, rfnniinriiUatr ptpUlip; % median drcutuviLltiitc pttpILlo, which cntlivljf fitUi the fof^ 
i_ men coMMiin; », 8, 3, 3, ffintr^forra papilljx* ; 4, 4, filtform papiUit); R, 6, verticil 

I^K foldfl and furniwM of i ' '»f (he ton^Ui* ; 6^ fi, fl^ (\, ^himlt^ at the bftflc t»f Um 

^H tongitv; 7, 7, ion«ilii ; ^; 9. nKuJiAit );lM9M>-eptg1otlidiuui fold. 

r: 



Hthin iUelf^ all the necessary fibers to insure those suoces* 
ive acts of a reflex ty|*e which occur during deglutition/ 



* it \h dt^ni^fd \ef Aome phyM!olo);itts thai th>? j^enmry jUamentM, which arc th« iRftin 
Ifi eictiini;; tb« reHex acY0 |H'rc%'ivi»d during dcj^utttiot^ nrv tho^o of this g1<Mao> 
plutfTIIgm) nrrre ; tiDiv the (Mpni^onr filatneittJi of ihu flflh tiervo diiitrihutod to the pakM 
■ad phftfTUx from Mtfokern gnngUon Aeem to ftbo fulfill thnl tmportMnt functioo. 



L 



470 



THE CRANIAL NERVES. 



and it is by this nerve that the second act of degmu 
chiefly excited and performed. 

The sense of taste, which is afforded by the glosso-pharyii- 
geal, is confined to the posterior third of the tongite. A sim- 
ilar distribution of its sensory fibei-s is remarkably illustrated 
in that case of Hilton's,' where an attack of tonsillitis 
duced a sympathetic /z^rr/zifir of the posterior third anly 
the lateral half of the tongue. 

Though analogy would lead us to suppose that a sHmulni 
applied to any part of the course of the gustatory fil)ers of the 
glosso- pharyngeal nerve would give rise to a sensation of 
taste and nothing else, the proof is not forthcoming; since 
tills nerve, as before stated, is a mixed nerve containing sen- 
sory fibers as weU as those of tast^. 



m 




Fio. 131, Fio. 132. 

VarieHes o/papiUa of the Um^m, (Sappey.) 

Ho. 181,— McdluTD-iised circumTdkte papitU; 1^ papilla, the baje cml/ being %i , 
it is seen that the Iwise is oovened with secondary papillw ; % groof« between 
papilla and the euiroundiiig wall ; S^ 3, wall of the papilla. 

Fi«, 132.— Fungiform, filiform, and hemispherical papilltr: 1, 1^ two f>'i 
covereil with ^econdarj papiUip; '2, % 2, filifonu papitlip; 8, a fill 
prolonpitions of which arc turned oatward; 4^ a Hliform papilla^ wni] vi?ni^ 
lonjratiunis ; 5, G, small (it! form paplthe, with the prolongations turned iiiwM<4 
filiform papillfflj with striations at their baaes ; 7, 7, hcixiispherical papUlK, \ 
apparent, eituated between the fungifonn and the filiform paptlhe. 

Bitter substances are ntiost tasted upon the ha^jk qf /J( 
tongue^ and sweet substances when placed %tpon the tip{ 
a point not without value in administering medicines. 

* *' Rest and Pain." For ahnilar eCfecta due to the fifth oenrCf §«« a pnrrimw 1 
' Mich. Foiter, op eii^ 



FUNCTIONS OF GLOSSO-PHABYNGEAL NERVE. 



471 



so-called "gustatory buds," which by some have been re- 
garded as specific organs of taste, are found also upon the 
epiglottis, which is wholly devoid of taste ; hence their func- 
tion can not as yet be considered as fully determined. 

As a means of refreshing your memory, the following 
classification of the branches of the glosso-pharyngeal nerve 
may prove of value. It will be seen that the tympanic branch, 
or Jacobson's nerve, is specially important, since it supplies 
portions of the middle ear which have been studied, when the 
auditory nerve was discussed, in their relation to the mechan- 
ism of hearing ; and also because it gives a filament to two 
of the i)etrosal nerves, whose functions have been considered 
in connection with the seventh cranial nerve.' 



A TABLE OF THB BRANCHES OF THE GLOSSO-PHABTNGBAL NERVE 
AND THEIR DISTRIBUTION.* 



GLOaO-niABTVOIAL 

(Ninth Cranial) 
Nbt& 



Trmpanio brandi, or 



"•™»''*» 1 Small p«ro«ilner»c. 

2. Carotid brandies. 

8. Pharyngeal branches (help to form ^b% vkarymg^ pUicm), 
4. Musoilar branches (to muscles of the pbanmx)! 
6. Tondllar branches (help to form the tonsfliar plems). 
^ 6. Lingual branches. 



EFFECTS OF SECTION. 

Section of the glosso-pharyngeal nerve is followed by a tyi)e 
of paralysis, in which deglutition becomes an act of extreme 
difficulty, and in which regurgitation of food into the nostril 
is particularly liable to occur. The sense of taste in the pos- 
terior third of the tongue is furthermore completely destroyed, 
thus tending to prove that the gustatory fibers are inherent to 
the nerve itself, and not the result of a communication between 

I Flint ascribes to the thorda (ympani nerve the ability to perceiTo only ealine, acid, 
and djfpiie qualities ; and to the gloeeo-pharyngeal nerve, the appreciation of wed, aUca- 
Unty bUUr, and meiallie tastes. Jaoobson*8 nerve probably controls the flow of saliTa; 
aeting in concert with the chorda tympani branch of the facial nenre. 

* Copied from the ** Essentials of Anatomy *' (Darling and Ranney). Putnam's Sons, 
New Torl^ 1880. 



472 

it iiUi\ jsiome other n^nre, a.s is ei:mu£d in 
latory fibers of the tifttL' 

It is stated, by some of the bter inyiHrtjflitaii mptm tim_ 
9abject, that the senae of taste is not aloDft onttftufl to 
trmgcie, bot exists also in tlie pfUarM of fh*^ fmmoet and 
walU of the pharynx^ and that sectioii of the j 
gnl oeire eauses an entire abolition of this powir of spedsl 
WBSm in these latter regions^ as well as in the posteaor Aiid 
of the tongoa* 

TBS ACT OF OJSOLCTITtaV AJm US 

The act of deglatition is, p^^ps^ moie pncuje g iy 
neeted with the glosso^phaiyngeal ner?e than with any othei; 
although that nerve aasists in the i)erfonnani.\^ of one stage 
only of the entire act For conTenience of description, it 
bfien the cnstom of physiologists to divide the act of de^at 
tion into three distinct periods- The tirst perio<l, oomi 





/ 



p^^r7^^==i7^^F^ 



Fio. 18S.— TUrf* budM/rom iht 



(fjJHe urtjan of tJkt roht^ 



the jia-Hsa^e of the bolns of food through the month, whirh is 
Tinder the control of the voluntary muscles : the second^ the 
I>a.ssiige of the bolus through the isthmus of the fauces and 
the pharynx ; th6 third, the passage through the oesoph: 
U} the canty of the stomach. 

In the Jlrst period^ the food is first seized by the lips, then 

■ See preTiom lecture on the fifth nerve, »nil wJi» the leeHtre upon the fidal MVfVu 
* Erpcriments seem U» point to ihc /unciform lod mrmmmaitmte pnfi/lm of the longvt 

u the chief egenti in peftetniig Uflte, if the fuiKtioii of tb* ** Ittit lM»d> ** of hemim lai 

ScbwAlbe 4re accepted u proven. See Fig. 13S. 




THE PH78I0L007 OF DEGLUTITION. 473 

forced between the jaws by the tongue and the buccinator 
muscles ; and by the teeth it is not only masticated, but is 
also mixed with the salivary secretion. When the food is 
ready to be swallowed, the mouth is first closed, as the act is 
performed with extreme difficulty when the mouth is open, be- 
cause the tongue can not properly act upon the bolus.* The 
tongue now becomes widened, so as to offer a large surface 
to the bolus of food, and, with the bolus placed behind it, is 
pressed backward along the roof of the mouth. In case the 
food to be swallowed happens to be in a liquid form, the 
tongue is so curved that its edges curl upward, while its 
dorsum is depressed in the center, thus forming a longitu- 
dinal groove along its entire length ; and the soft palate is 
so closely applied to the base of the tongue as to admit of a 
sucking force. 

The imi)ortance of the tongue during this period of the act 
of swallowing can not be overestimated. Animals, in which 
the tongue has been paralyzed by section of the nerves of that 
organ, exhibit the utmost distress in their efforts to bring the 
food to the back portion of the mouth, and are forced to so 
toss the head as to bring the force of gravity to their aid.* 
Drinking, also, becomes even more interfered with, and the 
tongue is no longer used to help in the act ; hence, various 
devices are used to bring the fluid where the reflex act of the 
fauces will help to carry it to the stomach. If it were not for 
the fact that, after removal of the tongue for local disease, 
the stump was of sufficient length to be of great assistance in 
controlling the bolus of food, such an operation would be a 
questionable procedure in surgery. 

It may be noticed, by those of you who have been follow- 
ing these remarks with care, that the glosso-pharyngeal nene 
has, as yet, had no influence upon the mechanism of degluti- 
tion, since the buccinator muscles are supplied by the facial 
nerve, and the tftngue by the hypo-glossal nerves, which have 

* For the clinical proof of this fact, the reader is referred to the effects of " facial 
diplegia.*' See page 448. 

* We see this also marked, but to a less extent, in patients afflicted with glosso-labial 
panlTiif. 



m 



THE CRAKIAl KFPTFJi^ 



not, a^ yet, been described ; but, as tlie sefrond and 
peri(Kls of the act are the most complex, and the second 
completely under the control of that nerve, the omintmi of 
the mechanism of the fii'st period^ until the whole could be 
considered together, was for the purpose of making the sab- 



-/^ 



Pio. 184. — C&riiifit of tht mouth and pKar^nx, Me, (Sttppojr.) 

Section in the medUn line of the face and Ihp superior purtioo of the ovclt. dc^imcil ' 
show the mouth id its relations to tbe na^l fosaap, the ph&fyiuc, ai ' 
sphenoidxl sinuses; % internal orifice of the Eiintaclimn lubo ; H. 
velum pendulum paUti; 5, anterior pillftr of tbc soft pilule; 6, ]> 
the soft palate; 7, tooi^tl ; S, Ungual poitioxi of the cavity of Qte phi 
|>1otti«; 10, flection of the hyold bone; 11, laryngeal portiofi of ibi: rwritv 
pharynx ; 12, carity of the laryns. 



ject moi'e easy of comprehension than if the different periods 
were considered separately feom each other. The effect 
section of the inferior maxillary branch of the fifth nei 
upon the act of deglutition has been mentioned in a preric 
lecture, but this effect is due, not alone to an absence < 



THE PHTSIOLOQr OF DEGLUTITION. - 475 

normal muscular i)ower of the muscles of mastication, but 
also to an anaesthetic condition of the mucous lining of the 
mouth, which renders the tongue unable to appreciate the 
situation of the bolus of food ; as has been proven by the fact 
that the same difficulty exists when section of the fifth nerve 
is made in front of the ganglion of Gasser, where only the 
sensory portion of the nerve can be injured, as when both the 
motor and sensory portions of the nerve are involved, after 
section below the foramen ovale. 

In the second period of deglutition, the bolus of food, 
by being crowded backward, tends to raise the soft palate ; 
and the levator palati muscle further assists in retaining the 
palate in this elevated position, while the superior constric- 
tor muscle of the pharynx causes the posterior wall of the 
pharynx to bulge. forward, and thus to meet the uvula. The 
posterior nasal openings are thus mechanically closed to the 
entrance of the food into the chamber of the nose, prepara- 
tory to the series of reflex movements which are to ensue, for 
the puri)ose of forcing the bolus downward into the oesopha- 
gus, and thence into the stomach. 

The larynx is now suddenly raised^ so as to bring the 
superior opening of that organ underneath the base of the 
tongue, which has been crowded backward during the first 
period, in order to force the bolus against the soft palate. 
Its soft structure renders it admirably adapted to mold itself 
to the irregularities of outline of the laryngeal opening. By 
this i)osition of the tongue, the epiglottis is also applied over 
this opening,* and the entrance of food into the larynx is 
furthermore guarded against by the approximation of the 
vocal cords by means of the adductor muscles of the larynx. 
The muscles which thus raise the larynx are the anterior 
belly of the digastric, the mylo-hyoid, the genio-hyoid, the 
stylo-glossus, and some of the fibers of the genio-glossus. 

Simultaneously with the elevation of the larynx, the pa- 

' It wtB formerlj supposed that tho epiglottis was the chief iDStrurocnt in prcvent- 
Ing the entranoe of food into the larjnz, but the large number of canes where tho 
epiglottis has been remoTed, and no difficulty in deglutition apparently produced, haye 
created a doubt as to ita importanoe. 



476 



THE CRANIAL 



lato-pliaryngeal muscles contract and raise the Iowa ' 
the pharynx^ thus shurtenmg the length of that orgiiii iiu 
tending to draw the pharjTix over the bolus of food^ ve 
much as a glove is drawn over the finger ; while, at the 
tune, the ciu*ve uf the posterior pillars of the pharrnx 



fif 



131 



fat 



Fig. 135. — JfMctfH o/ ihe phnrvni^ rte. (8ttpi>ej.) 

I, 9, 8, 4» 4» superior (sonstrictor ; 5, 0, 7, 3, midillv c*m«tn<;tor ; 9, 10, 1 1, 1% [afe 

strictor; 13, 13, atylo-pharyngcua ; 14, ?tTlo4iyoid uiiisde; 15, 9tf-)(>{;loMus * 
hyo-gloeaus ; 17, mjlo-hjoid muscle; It^, buccinator muscle; 1(^, i«QK>r {mlali; 
IcTAtor pukti. 



made straight, and, by the approximation of these maa 

to the sides of the uvula, the opening of the pharynx tnt^ 

the nares is now completely occluded* 

The constrictor muscles of the pharynx now come tnta 



THE PHYSIOLOGY OF DEGLUTITION. 477 

play, contracting in succession from above downward ; the 
I)08terior pillars of the fauces, by their approximation, pre- 
vent the bolus from again entering the mouth ; and it is thus 
forced to enter the oesophagus. 

It is apparent that most of these movements are of a re- 
JUx cTiaracter^ and are excited by the presence of the bolus 
of food, which passes out of voluntary control as soon as it 
passes the anterior pillar of the fauces, at which point the 
second period of deglutition maybe said to commence. Every 
reilex act presupposes some sensory filaments to convey the 
impression to the brain, and certain motor filaments to trans- 
mit the impulses to the muscles destined to act upon the 
bolus; it is now believed that the glosso-pharyngeal nerve 
I)ossesses both of these sets of fibers, as well as those control- 
ling the special sense of taste. This nerve may then be con- 
sidered as a nerve of taste, a nerve of motion to the pharyn- 
geal muscles, and the true ^^excUory nerve^' of the act of 
deglutition. 

The importance of the soft palate in the act of deglutition 
is particularly shown during the swallowing of liquids, since 
it has to be closely applied to the base of the tongue, in order 
to allow of a x>artial vacuum within the cavity of the mouth, 
and thus to draw the fluid along the furrow formed by the 
curving upward of the edges of the tongue. This fact is clin- 
ically shown by patients affected with paralysis of the velum,* 
who experience great difficulty in swallowing liquids, since 
the fluid is liable to escape through the nose. A case of this 
• character is reported by B^rard, where a young lady wa« 
obliged to free herself from all observation whenever she at- 
tempted to drink, as the escape by the nostrils was so profuse 
as to occasion embarrassment. 

The prevention of the entrance of food into the cavity of 
the larynx, as has been mentioned, is insured : first, by the 
base of the tongue ; secondly, by the epiglottis ; and, thirdly, 

' ParalyBifl of certain muscles of the soft palate occurs when iha faded nerre is im- 
paired behind the point of origin of its petrosal branches. For particulars of this diag- 
nottic fTmptom, the reader is referred to page 440. 
88 



47« 



TBE CRANIAL XERVES. 



i 



by the approximation of the vocal cord»; but ihar 8uch acci- 
dents do still happen from attempts at inBpiration * dtrnn^ 
eating is attested by the violent congliing excited^ and bj 
the instantaneous expulsion of the foreign substance, imlp?» 
it should chance to become mechanically arrested in the laiyox. 
Ltmget accoimts for the symptoms excited by such an acci- 
dent as the result of an exquisite sensibility posaeaeed by thr 
mucous lining of the upper part of the larynx. It is weD 
attested that the danger of entnince of fluids Into this oiigan 
is far greater than in the ciise of solids ; and the act of gar- 
gling is especially liable to be followed by such an occqit^qd^ 
since the laiyiix is much wider open than in the act of degl 
tition. In the administration of anaesthetics to patients w 
have eaten largely before the hour appointed for sui^gi' 
relief, a great danger of the entrance of vomited matters 
into the cavity of the larynx is encountered, since the sensi- 
tiveness of the mucous lining is destroyed, and the expulsime 
efforts of Nature are often wanting.* 

ITie tJiird period of the act of deglutition is confined to 
the oesophagus, through which the bolus has to paas to readi 
the stomach. The dowTiward movement of the bolus is aa- 
sisted by alternate contraction of the longitudinal fibers of 
the tube, which shorten it and tend to dra^v its walls upward 
over the bolus, and contraction of the circular fibers, which 
constrict the tube and force the bolus downward. The fiot 
that gravity has little, if anything, to do with this dowTiwarf 
movement is proven by the fact that the i>osition of the body 
does not seem to affect it, while acrobats are often known to 
perform the feat w hile standing upon the head or hands. The 
time consumed in the passage through the cpsophagus v«i 
estimated by Magendie * as about two minutes in animalay bnl 

* As occurs during aUftcka of laugfaing, hiccough, ete^ mhttt food b prwanl hi lb* 
mouth« or during too huty fto effort to consume food, 

' In CMOS where this accident occurs, the tongue should be foraihly drmim ool of tlie 
iDomfh, to t« to pull up the epiglotitft, nnd the foreign body cxti««M bf the in^er, if 
poMfhle, or, if not, the patient should be held bj the feet, tnd thoB, hf shskiiig tlw pi* 
tient, grnrit? maf help to dislodge it I once sored the life of n nana hf Hili mmm 
when nil others hud failed, and fatal asph^ila i 

* "Journal dcPhraioL*' 



THE PHYSIOLOGY OF DEGLUTITION. 479 

it is probably much shorter in man ; although we are often 
conscious of a delayed tennination of the act, and are forced 
to hasten it by the drinking of iluids, as most of us can attest. 
It is probable that this i)eristaltic action of the oesophagus, 
like that of the intestinal canal, is partly controlled by the 
nervous influence of the sympathetic system, although the 
pnemnogastric nerves have an extensive distribution to and 
a very maikfid control over this organ.' 

Deglutition is e^erUially a reflex act^ save in its first 
period, when volition plays an important part. It can not 
take place unless some stimuhia is applied to the mucous 
lining of the fauces ; and those apparautly voluntary acts of 
deglutition which are produced when no 16od is within the 
mouth are undoubtedly due to the swallowing of saliva, or 
to irritation of the fauces by the base of the tongue Itself. 
When we tickle the fauces, we can see all of the act of deglu- 
tition, confined to the second period, artificially produced ; 
and this irritability of the fauces is so extreme in some per- 
sons as to render any attempt to examine the throat one of 
difficulty, and often a cause of refiex vomiting. So impor- 
tant is the education of the throat to enable the patient to 
tolerate the presence of instruments, that all surgical proced- 
ures upon the larynx, if performed from within the mouth, 
require often months of training to enable the jxatient to assist 
the oi)erator in a step whose execution may be a matter of a 
few seconds only. All forms of local applications are used 
to insure an ansesthetic condition of these parts, and the in- 
ternal administration of medicinal agents is, furthermore, 
often required to render such procedures within the cavity 
of the larynx i)ossible. 

That the ceivter for the reflex act qf deglviition is confined 
to the medulla oblongata is proven by experiment on animals 
whose brain has been entirely removed, with the exception of 
the medulla, when irritation of the fauces will still continue 

' Midiftel Foster regards this third act of deglutition as more closely dependent upon 
the emiral nervout tyttem than the morements of the intestinal tract, and attributes it to 
reiei actioii dns to the bdos. 



480 THE CRANIAL NERVES, 

to produce all the movements of the second sta^ of that 
act. 

CLINICAL POINTS OF INTEREST PEBTAINING TO THE OLOSSO-FHABYX- 

GEAL NEBVE. 

The intimate association which apparently exists between 
the fibers of this nerve and the sense of taste, the movements 
of the pharyngeal muscles, and the reflex acts excited by the 
presence of a bolus or of some foreign source of irritation to 
the isthmus of the fauces and the walls of the pharynx, would 
seem to suggest that any impairment of the glosso-pharyngeal 
would be followed by clinical evidences of imi)erfect i)erfonn- 
ance of each and all of these functions. It is, however, to be 
regretted that the questions of the course, origin, and func- 
tions of the chorda tympani nerve, the exact distribution of 
the fibers of the glosso-pharyngeal nerve to the tongue, and 
the source from which this latter nerve derives its motor fila- 
ments, are, as yet, disputed points among physiologists ; and 
the sources of doubt are not removed, but rather increased, by 
the results of pathological observation, since they often seem 
contradictory, and thus prove rather a source of embara^js- 
ment than an aid to definite conclusions. 

One would naturally suppose, provided that he was fa- 
miliar with the symptoms of that disease, called by Duchenne 
''glosso-labio-laryngeal paralysis" (although the word ^'pha- 
ryngeal" is often used in j^lace of "laryngeal" to express the 
same condition), that the difficulty experienced in deglutition 
would certainly indicate that the nerve which apparently pre- 
sides over that function would be found in a state of disease ; 
but, on the contrary, the glosso-pharyngeal nerve is not re- 
I)orted, to my knowledge, as having anything to do with that 
affection. We must, thei^fore, be forced to infer that the 
motor filaments of the pharynx are, to a great extent, con- 
trolled by other nerves ; and that, if they are api)arently 
branches of the ninth cmnial nerve, they are to l>e accounted 
for as fibers derived from communicating filaments from other 
sources. 



CLINICAL CONDITIONS CAUSING HYPERQEUSIA. 481 

Hirschfeld claims to have verified a branch of the glosso- 
pharyngeal nerve which extends to the anterior two thirds of 
the tongne; hence the strong probability that it partially 
controls the sense of taste in that portion as well as in the 
jKDsterior third of the organ. Stannius, by experiments, 
thinks that he has established the function of this branch, 
and he attributes to it the power of perception of hitter 
svJ)stanc€S only, the other varieties of taste sensations 
being presided over by the chorda tympani nerve or the 
gustatory branch of the fifth nerve. We know, clinically, 
that the conditions of hyperaesthesia and anaesthesia of 
the gustatory nerves are verified by many interesting phe- 
nomena; and we must be content to wait for the solution 
of the other mixed problems of gustation, until they are 
solved by further clinical, physiological, and pathological 
observation. 

The condition of gustatory hypercesfhesia^ called also 
'''' hyper geusia^'^^ ' is very marked in certain patients who fit^ 
in an anaemic and nervous condition, while it is a frequent 
phenomenon in hysteria and in melancholia. In such cases 
an apparent gustatory sensation may be often excited by the 
application of an electric cur^nt to the cervical or upper 
dorsal region of the spine. 

True gustatory hyperaesthesia may express itself as an in- 
crease in the delicacy of the gustatory sensation, so that ex- 
tremely small quantities of sapid substances may be perceived. 
We thus occasionally meet with hysterical patients, who can 
I)erceive the taste of certain medicinal agents in a solution 
which to the healthy subject would be tasteless. It may ex- 
press itself, again, as an unnatural enjoyment of food, or a 
loathing of certain dishes which convey a sense of taste which 
does not in reality exist. In facial paralysis of rheumatic 
origin, abnormal gustatory sensations are sometimes present, 
as sweetish, sour, or sapid tastes, within the mouth. In the 
insane, hallucinations of the special sense of taste, usually of 

' See experiments of Valentin and Kcppler, made to determine the exact degree of 
guitaloiy soisibility and ezdtability. 



482 THE CBANIAL NERVES. 

a disagreeable character, are often present, and indinur 
disease of central origin. 

The condition of gustatory anctsthesiay called ^^ ciffeusia,'" 
comprises all those phenomena which indicate either a [lartiil 
or complete loss of the sense of taste. Tims, the tongue 
be able to appreciate certain substances, and be insensili :^J 
others, while the ansesthetic condition may be circumscrih^^f 
or diffused, as regards its anatomical distribution, affecfioiE: 
either the tip of the tongue, its root, or one or both side*. 
This abnormal state is observed after paralysis of the trik^* 
minus, severe injuries to the trigeminus or the glosso-iihan. u 
geal nerves, intra-cerebral growths which create compr^asii 
of the glosso-phai'j-ngeal or trigeminus,' and atrophy of t 
nerves, as the result of compression, and of disease of their i 
herent fibers. As a rule, when this condition exists, we sh; 
find a similar condition of the optic, olfactory, trigeminus 
pneumogastric, spinal accessory, or some of the cutaneoi 
branches to the face. 



TUK PNEmiOGASTRIO, OR TENTEI NERVE, 

Ovnng to the numerous connections of the pneumti 
with other neiTes, its varied and extensive distribution, 
the important character of its functions, tlds may properly 
regarded as one of the most remarkable nerves of the whc 
body. It has been often known liy the name of the *'par 
f/um,-^ from the wandering course of its fibers, which 
distributed to five different vital organs, viz, ; the he 
lungs, stomach, liver, and intestines, as well as to many otl 
parts of secondary impcirtance. 

This nen e, like the seventh, eighth, and ninth nerves, ; 
^considered by comparative anatomists as belonpn^ to tl 

» Id the case reported bj Botu*Ker, although tigen^ existed.^ the potitjm otrnpiiiia 
of a coustaat burning and bitterness within the mouth. An autopsy ahowed lli« pr 
of a tumor of the base of the brain, which had caused atrophj of the gloaack-pliAr 
and pQeumo^astnc nerves by a steadr oomprcsBton. Loo^et reports cas«4 «h#t« iht 
neryea passing through the jugular foramen were all more or leaa deitroyed by p rmwr t 
from a BimihLr cause. 



I 



class of spinal neires, since it arises directly and entii-ely from 
the upper portion of the spinal rord. Its supei'ficial point of 
origin lies in the groove between the oUmiry and nsiiform 
bodies of the medulla, while its deep point of origin may be 
traced to a gmy nucleus in the floor of the fourth ventricle, 
slightly below the nucleus for the glosso-pharyngeal nerve/ 

There is a vei-y close affiliation between the deep fibers of 
the pneumogastric and glosso-pharyngeal nerves within the 



Fto. 186L— 




I 




(UirFchfeld.) 



with the f AdAl; 8, 8, pmeitmogfusfri 
ft, iublmgiiiil tkfTVQ ; 6^ superior <- 
arttitle t»f ifte firiU /tfvj cttrvicnl 

■ ' ^ympaibHic; 9, m 



i^tofnoaes of Hie gloH>o-pharyiig«l 

f of thp sympathetic ; 7, anajdantotie 

:id branch of the EUperior ccnrkal 

1 J:.i iiimrtij ; 10, branches of this nerve to 

11, branch to the Kustiichmn tiitH.- ; 12, br)*ndi to I he fcneMra 

o , ..., ,ji*h to the fcnctfr^' mtunrU; 14, enti^mal (Ii.H'p pt'lnHis ncrvf ; 1ft, 

tcmal deep pctroiia nerve ; IG. ion ; 17, auricular hr<int*fi **/ tftf fmnmut- 

IH, atitjsfoiitOKiH of tht I ft trilfi the tpinaf nctfvory : IW, irw^M/a- 

yf th yfric trith tku kuUitntfUtU : 20, anai4t(»mo«U of the ipinni ftcce»- 

With u. pdr of ciTvical nerves; 21, pharyngeiU plcxui ; :i2» euperlor 

ncrvt*. 



[ibstance of the medulhi oblongata, so close indeed aa to lead 
>me authors to consider them Identical with each other* 
'These deep fibers may l>e trar*Hl, in part, into th«^ substance 
^^of the restiforra body, a small bundle towunl the ren^lielbiritj 

^H * Snt pnrriouM page af tltin iteclbn, in wbJch tli« dee|> ort^n uf the oeirc U dbeotJitdL 




484 



THE CRANIAL NEEVE3. 




Fio. 187. — A diagram thawing the branches of distrifnttion and communication of the 
pncutnogastHc nerve. Cenncal portion of nerve. 

1, the filaments of origin of the pneumocjastric nerve; 2, the ttpiual acetsson/ nervo escap- 
ing from the medulla oblongata, below the pneumogastric nerve ; 3, the upper com- 
municating filament between the pneumogastric and the spinal aecessorjf nerves (often 
absent); 4, the ^^ ganglion of the root^'' situated in the jupilar foramen ; 6, the Jugu- 
lar forameny showing the transmission of three nerves ; 6, the communicating filament 
between the pneumogastric and the glosso-phargngeal nerves ; 7, the glosso-pharyngetd 
nerve, from its point of origin to its escape from the cavity of the cranium ; 8, the 
** ganglion of the trunk" of the pneumogastric nerve; 9, the lower Jiiatneni of 



QANQLIA OF THE PNEUM00A8TRI0 NERVE. 485 

communication between the pnettmogastrie and spinal aceeuory nervet, which probably 
controls the muscles of the larynx concerned in phonation and respiration ; 10, the 
communicating filament from the arcade, formed by the first and second cenrical 
nerves ; 11, the communicating filament from the facial nerve, which helps to form 
the auricular branch of the pncumoga^tric or "Arnold's nerve " ; 12, the three tets of 
filaments which join the pneumogastric nerve to the superior cervical ganglion of the 
sympathetic system; 18, the auricular brandi of the pneumogastric, or *^ Arnold's 
fXTVf," partly formed by the facial filament (11); 14, the branches to the ^'pharifn- 
gral plexus" formed also in part by the glosso-pharyngeal ; 16, the superior laryngeal 
nerve, supplying the mucous lining of the larynx and the crico-thyroid muscle; 16, 
the " depressor nerve of tJie hearty" formed by two roots, one from the pneumogastric, 
and the other from the superior laryngeal nerve ; * 17, the inferior or ricurrntt 
laryngeal nerve, windim; around an artery (19), and then returning to the larynx to 
supply the muscles of phonaticm ; * 18, the cervical cardiac nerves (sometimes three 
in number), going to the cardiac plexus ; 19, the suhdavian artery (if on the right 
side), and the arch of the aorta (if on the left side of the body). 

and a few toward the cerebrum ; but the larger portion pa^s 
to the median line of the floor of the fourth ventricle or de- 
scend into the substance of the medulla oblongata. 

The pneumogastric nerve emerges from the jugular fora- 
men as a single tioink, but immediately develops two gan- 
glia^ the upi)er of which is called the ^^ jugular ganglion^^'* 
or the '' ganglion of the root^^^ since it lies close to and some- 
times within the foramen of that name. After the nerve 
emerges from the foramen, another ganglion, about one quain- 
ter of an inch in length, is developed, called the ^'ganglion 
qfthe trunJc?'' Within the jugular ganglion, an interchange 
of fibers takes place between the pneumogastric and spinal 
accessory nerves ; and it seems clear that the laryngeal and 
pharyngeal branches (which are among the most decidedly 
motor of those given off from the pneumogastric) may all, in 
great part, be traced backward into the spinal accessory 
nerve. 

The researches of Valentin, Morganti, Longet, and others 
seem to prove that the pneumogastric nerve at its root pos- 
sesses no motor power, but is entirely an afferent ner\'e, al- 
though Stilling, Wagner, Muller, Volkman, and Bernard fail 

* For the physiological effect of stimulation of this nerve, see the late researches of 
Cyon and Ludwig upon this nerve in the rabbit ; also text-books of physiology of Michael 
Foster, A. Flint, Jr., and others. In man, this nerve is probably associated with one of 
the cardiac nerves. 

* The filament of the spinal accessory (No. 9 in the cut) Ib supposed to afford to 
thif nerve its motor power, having simply used the sheath of the pneumogastric as a 
■Mans of protection In iu course down the neck. The physiological import of this nerve 
■bowt the Tital neoeiaity for tuch protection. 



486 



THE CRAmAl XEEVEX 






to attribute all the motor tibers ul tixib nerve to eiilitr :! 
8pmal accessory or glusso-pharyiigeal nerves, and luiiiDtiu 
that motor libers may be demonstrated mthin the root of tli 
pneumogastric above the jugular ganglion. 

In regard to its trunks there can be no doubt fli.ir 
pneumogastric is txj be considered as a nerve of doul)!^ 
dowments, although it is certain that these endowment^i 
very differently distributed among its branches. That 
capable of conveying those impressions which become se\ 
tions when communicated to the sensorium Is experimentallr 
proved by the fact that, when its trunk is pinched, the ani- 
mal ^ves signs of acute i>ain ; and it is also evident from th«^ 
painful consciousness we occasionally have of any abnormal 
condition of the organs which it supplies. 

BRAKCHES OP THE PNEUMOOABTBIC NZBTB, 

The pneumogastric nerve, by means of its numerous poiai 
of distribution, participates in the operations of deglutUiQ: 
phonation, respirationj the eircnlaiion of the blood, 
the process of digestion. To fully describe the variatif>n5 la 
its course from above downward, and the tlistribution of 
branches to the various organs (in all of their physiologic 
bearings), you must, of necessity, be carried into a discus^- 
sion of the thoracic and abdominal viscera and the physio* 
logical acts which they perform, A hasty enumeration of t 
general course of the fibers of this nerve can, therefore, oi 
be given hem, reserving the many points of interest connect- 
with it for other lectui*es, when the viscera will be <H)nsi<le 

The efferent fibers of the pneumogastric nerve include 
tain motor branches which are distributed into the plm 
the larynx^ the CBsophagus, the stomach, and the intesi 
canal. 

The pharyngeal branches help to form the pharyngeal 
plexus of nerves, and thus to aid in the movements of 
muscles of that organ during the second period of deglntiUoi 

> Sec lecture upon the gtoaso-pbAryngcil ii«rire^ whcra the «!t of d«gttttitioii U 

dlflcussed. 




US^™ 




DISTRIBUTION OF PNEUMOOASTRIO NERVE. 



487 



It is also probable that these same muscles tend to modify 
the Ume and quality of the voice, and also to assist in the 




'./r.. 



38 



27 



Fio. 188. — Thoracic and abdominal portion of the nervf. 

SO, the tharaeie cardiac ncnrcB, anBinting to form the cardiac plexus ; 21, the filaments of 
ooiDmiuiication between the pneumagattric nerve and the thoracic ganglia of the sym- 
pathetic system ; 22, the branches given off by the pnciinH»fi^tnc nerve to assist in 
forming the pottcrior puimonarif plexus ; 23, the branches piveii off to assist in form- 
ing the anterior pulmonary plexw ; 24, the branches wiiich form the cuophageal 
planuy and assist in the performance of the thinl period of the act of deglutition ; 
26, the gastric branches^ supplying the coats of the stomach ; 26, the hepatic branchety 
aooompanying the portal system of veins ; 27, the inieiitinal branches^ controlling, to 
a largo extent, the porisultic action of that canal ; 28, branches which can be trmoed 
to tbe kidneys, the spleen, and the supra-renal eapstUes, 



PHY8I0L00Y QF PNEUM00A8TRIC NERVE. 489 

of the peculiarity of its course, since it winds around the sub- 
clavian artery before returning to the larynx, upon the right 
side of the body, while the left nerve winds around the arch 
of the aorta, and then turns backward, to be distributed 
to the muscles of the larynx. It is by means of these laryn- 
geal nerves that the muscles which mone the vocal cords^ 
and thus control the voice, are supplied ; while the same mus- 
cles are important agents in so adapting the size of the open- 
ing between the vocal cords, during inspiration, as to allow 
of an unimi)eded entrance of ah* to the lungs.* As the infe- 
Tior nerve is the one which supplies all of the laryngeal mus- 
cles but the crico-thyroid and a portion of the arytenoid, it 
becomes to the physiologist a nerve of great importance, since 
the acts of respiration and phonation are directly under its 
influence. Experiment seems to have proven, however, that 
the laryngeal nerves, although apparently deriving their mo- 
tor power froni the pneumogastric, are, in reality, but fibers 
of the spinal accessory nerve^ which have used the sheath of 
the pneumogastric nerve simply for protection in their pas- 
sage through the neck. The spinal accessory nerve is, there- 
fore, sometimes called the "superior respiratory nerve of 
Bell," since it controls the movements of the laryngeal mus- 
cles during the act of inspiration ; ' which are the highest, in 
point of situation, of any of the respiratory muscles. 

The branches to the cesophagus^ stomachy and intestine 
are the principal agents in promoting the peristaltic action of 
the alimentary canal, and they thus aid in the acts of degluti- 
tion and digestion. It is probable, also, that the pneumo- 
gastric nerves are capable of directly affecting the secretions 
of the alimentary canal, although the sympathetic system is 

' The researches of Bernard have done much to call profcpsional attention to the fact 
that the pneumogastric and Bj)inal nen-es arc alone involved in ordinary respiration, but 
that, when it becomes necessary to brinp; the respiratory movements into perfect accord 
with the requirements of animal life (as in adapting the action of the muscles of the 
larynx to production of voice), the spinal accessory nerve becomes an indispensable aid. 

• This statement is one that will admit of question. The reader is referred to the 
experiments of Bernard and Bischoflf (as given on a subsequent pajrc) for the difference 
between the effect of the spinal accessory fibers ui>on the glottis from those of the pneu- 
mogastric itself. 



490 



THE CBANIAL NERVES, 



still regarded as the nie^ans by wliirh these nerves exert tlieir 
influence upon that portion of the body* 




TiQ. 140. — Nervea o/ ifu larynx^ posterior Fio. 1 4 L — iWrvev of the UirfAjL^ laUrd 

view, (After Sappcj.) c4«ne. (After Birschfeld.) 

FlO-UO.'-l, 1, sttperior laryngeal nerves pasfiln^ thf^H^h ih** thvro<hYoid mombrmtie ; % I 
extertml lar^D^eal branch ^uppljing the t " 1, •Mending t 

distributed t<i the mucotig raembr&De of i liie brmoobM < 

ted to Ihe muoouM membrane of the eplgloui^ nu>i Uic «i ^ kvuM-cpiglotlidatn fol40; i|^ 
desoendiDg braochcs pas^dng to the muoood tnembrmiie corering the posterior turllici 
of the larynx (two of ihese^ of considerable size, croeB the trTicnoid muaole lo mpplf 
the mucou9 membrane lining the walla of the vestibule) ; 6^ branch connecting tbe 
superior with the inferior lftrynp:eal nerve ; 7, the name branch divided near iu pohit 
of origin; B^ 8, inferior laryiigenl nerve; 9^ branch to the potterior erieo-ArniiEnQld 
muscle, which is here divided in order to show the next nenre ; V\ branch lo tlM 
arytenoid winding under the lower border of the ma«ole so a^ to enter it from itt 
inner surfiice ; 11, branch to the lateral crioo-arytenold muidfi; 12, branob to Ihm 
thyro-arjtenoid muscle. 

FtuJ41,— a, section of the h^^oid bone; 6,iioctioQ of the thyroid cartilaf^; e, th]rro4qraM 
membrane ^ rf, cricoid cartilage ; <?, tradiea ; /, cesophagua ; g, o-J-i— *u . ^^ attpcrlor 
oomu of the thyroid cartilage ; t, great cornu of the hyoid bone ; hyrtwhyold 

ligament; /, thyro-hy old memb nine ; m, posterior crico^r)'toti> ; n, lat<ifa] 

crico-arytenoid muscle; o, thyro-arytenoid muscle; /j, baae of th»i tonguv ; I, f^cnrv 
pent biryngeal nerve ; 2, branches given off from thi* nerve to the posteirior rrloo- 
arytenoid mudcle; 3, branch to the lateral crico-arytenoid munele ; 4, bT«noh to tlnr 
thyro-arytenoid muscle ; 5, branch to the arytenoid muscle ; <J, right superioir laryn- 
geal nerve ; 7, Anastomosis of this nerve with the inferior kryngeal ; 6, dcacftudiog 
branches from the superior laryngeal ; % middle brancUcfl of tjbe aamit lierf« ; 10^ 
ascending branches. 

In addition to the branches, which are considered as 
greatest physiological importance, certain other w/>tor 




PHYSIOLOGY OF PNEUM06ASTEIC NERVE, 



4DJ 



"of 

Hue: 



now traced with tolerable certainty to the trunk of the 
neumogastric nerve, which are not unimportant. Thus we 
may include certain nei'ves which supply the plain muscular 
fibers of the trachea and of the larger bronchial tubes, fiber» 
which exeit a ram-viotarial inflMence upon the blood-vessels 
of the lungs, an inJiihitory nerm far the hearty and certain 
fil^i-s which ai^ distributed to 
the lungs and the heart, which 
are supposed to exert a trophic 
in/lvenee. 

The properties and functions 
of the cardiac nerre, and in 
hat way the pneumogastric 
nerve influences the action of 
the heart, are physiological 
questions of the greatest impor- 
tance. It is now known that 
Ieection of the pneuraogastric in 
the neck, instead of arresting 
Ihe action of the heart, in- 
preases the frequency of its 
contractions ; while galvanism 
of the divided ends causes the 
heart's action to stop during its 
diastole^ if the cnrrent be a 
I>owerful one, and, if a weak 
one, the heart's action is propor- 
tionately slowed* 
^B The drfyressor nerre of the 
^^^art is shown,* in the diagram- 
^miatie representation of the pnen- 

^Pnogastric nene and its branches, to arise from two filaments 
d«>rived, respectively, from the pnenmogiistric and thesui>erior 
lauyngeal nerves. The importance of this nerve in explaining 

' For th« fMcthml of uHgln of ihif* n«rrc, ioo the diiRnimtn»iio pliiU? of ilic «pi»f? 
\U *tt (he |)n«Mitno||;ti»trie nerve, page 484, While tho diiigram jUitfttrftten the cuuntnicv 
on of thin tir>fv4>, tin found in Xha rabbit hy Cyoti, it (a etill quc^oilonabl^ whethc*r a ftiiut- 
' tnrrthoil of ori^U\ can be dcmoniitratcd in man. Ttmt t\w n^rve i'sihU \n nut n matter 
f doubly but it U iiivpoteiblc to fmMralj »taU) iU na^sthudof ori^nn .^^ M« f.M .