A treatise on intracranial diseases: inflammatory, organic, and symptomatic

Front matter

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UNITED STATES OF AMERICA.

Preface

The present work on Intracranial Diseases embraces inflammatory, organic, and symptomatic affections of the brain and its membranes — diseases which are quite as important, and as frequently met with in practice, as those contained in my work on Diseases of the Nervous System. Though intended chiefly as a Supplement to the latter work, I have endeavored to render it so complete in itself, as to present within a moderate compass the leading views of those most advanced in cerebral pathology and therapeutics, and, at the same time, furnish a safe and sufficient guide to those who may be disposed to consult its pages for information on these interesting and important subjects.

As the diagnosis of intracranial diseases is frequently attended with considerable difficulty, I have prefixed a few chapters on matters pertaining to the regional diagnosis of cerebral affections ; for, as M. Charcot has well said in the preface to the American edition of his Lectures, " The exposition of the principles underlying the doctrine of cerebral localization seems to have now become a necessar}^ chapter of introduction to the practical study of diseases of the brain."

In conclusion, I desire to acknowledge with grateful feelings the generous appreciation bestowed by the profession upon my former writings, especially those pertaining to the nervous system, and to express the hope that the present addition thereto will be found to possess merits entitling it to a like favorable reception.

C. P. H.

CHAPTER I. Functions of the Cerebrum

Discovery of the cortical centres — Ferrier's experiments on the brain of an ape — Summary of the results obtained by Fritsch, Hitzig, and Ferrier — How the discrepancies between them may be accounted for — Methods employed in the investigation — Situation of the motor centres in man — Goltz's method of research — Broca's discovery confirmed — How these discoveries are regarded by Eckhard, Schiff, and others — Lussana and Lemoigne's objections — Brown- S6quard's views — 'Arguments in support of the cortical theory of localization — Objections answered — Confirmed by clinical experience — Law of functional substitution — The sensory centres — Facts which appear to be satisfactorily established — Volition and intelligent consciousness — The seat of intelligent language in man, 17

CHAPTER II. Functions of the Cerebral Ganglia

Meynert's ganglia of the tegmentum pedunculi and pes pedunculi — Effects produced by electric stimulation of the corpora striata — Hemianesthesia — Luy's four divisions of the optic thalamus — Functions of the corpora quadrigemina — Experiments of Hensen and Voelkers — Unilateral destruction of the corpora quadrigemina — Adamiik on stimulution of the nates — Expression of the emotions — Muscular coordination — Epileptic moans and cries — Functions of the crura cerebri and pons Varolii — Automatic movements — Functions of the cerebellum — Vertigo — Priapism — Diabetes, 30

CHAPTER III. Functions of the Bulb

Receives and transmits both sensory impressions and motor impulses — Crossed paralysis — Reflex coordination — The respiratory centre — The cardio-inhibitory centre — The vaso-motor centre — The emotional centre — The centre for deglutition — The cesophagal and gastric centre — The salivary centre — The centre for articulate speech — The diabetic centre — General centre for the coordination of muscular movements, ...... 38

CHAPTER I. Cerebral Lesions

What lesions are of special value in establishing the theory of cortical localization — No known systemic lesions in the brain — Predominant influence of vascular lesions — No known anatomical centres of mental affections — Differentiation by elevation of temperature and by motor phenomena— Latent disease of the cortex — Convulsions — Sensory disturbances — Aphasic symptoms — Word-deafness — Paralysis — Monoplegias — Associated symptoms — Transient paralysis — Destructive lesions — Secondary degeneration, ... 41

CHAPTEK II.

Lesions of the Basal Ganglia.

Cerebral hemiplegia accompanied with cerebral hemianesthesia — Central cerebral hemiplegia — Temporary and persistent hemiplegia — Cerebral hemianesthesia — Destructive lesions of the internal capsule — Vaso-motor disturbances — Hemichorea — Thalamic lesions — Homonyomous hemiopia — Athetosis and unilateral tremor — Disorders of psycho-motor reflex actions — Lesions of the nates — Lesions of the testes, . 47

CHAPTER III. Lesions of the Cerebellum

General character of cerebellar symptoms — Cerebellar paralysis — Vomiting — Amaurosis — Incoordination of movement — Lesions of the middle lobe — Excitation of the genital functions — Lesions of the middle peduncle — Vertigo — Anarthia, headache, etc. — Diagnostic lesions, .... 53

CHAPTER IV. Lesions of the Cerebro-spinal Isthmus

Systemic lesions — Alternate paralysis — Lesions of the pons Varolii — Apoplectic symptoms and rise of temperature — General paralysis — Epileptiform convulsions — Diabetes mellitus and insipidus — Albuminuria — Muscular rigidity — Emotional weakness — Lesions of the medulla oblongata— Implication of special nerves — Disturbances of respiration, circulation, etc. — Value of negative symptoms, 57

PART II. Intracranial Diseases

SECTION I.

Cerebral Affections.

CHAPTER I. Anemia of the Brain

The intracranial circulation — The cerebro-spinal fluid — The three principal forms of cerebral anaemia, namely, the irritative, apoplectic, and syncopal— Symptoms — Symptoms in the aged — Syncope — Vaso-motor anaemia — Paresis and paralysis — Causes — Diagnosis — Prognosis — Morbid anatomy — Pathology — Treatment — General and special indications, 62

CHAPTER II. Cerebral, Hyperemia

Active and passive hyperaemia — Symptoms of excitation— Symptoms of depression — Headache — Hyperesthesia of the special senses — General anaesthesia — Irritability of the vascular system — Krishaber's investigations — The delirious, convulsive, and apoplectic forms — Causes — Diagnosis — Prognosis — Morbid anatomy — Pathology — Treatment— General indications— Special indications, 73

CHAPTER III. Cerebral Apoplexy

Definition— Symptoms — Hemiplegia — Causes — Cerebral haemorrhage — Haemorrhage into the cerebral membranes — Embolism of cerebral arteries — Cerebral hyperaemia — Sunstroke — Uraemic and alcoholic intoxication, . 91

CHAPTER IV. Cerebral Hemorrhage

Definition — Comparative frequency in different parts of the brain — Symptoms — Apoplectic and paralytic forms — Variations in the animal temperature — Conjugated deviations of the eyes and head — Symptoms of the second stage

Acute bed-sores — Hemiplegia— "-Facial paralysis — Paralysis of the extremities — Secondary contraction — Causes — Diagnosis — Prognosis — Morbid anatomy — Pathology — Treatment — General and special indications, . . 93

CHAPTER V. Cerebral Thrombosis

Definition — Symptoms — Marantic thrombosis — Venous thrombosis in the adult — Causes — Diagnosis — Prognosis — Morbid anatomy and pathology — Atheromatous degeneration of the cerebral arteries — Illustrative case — Heubner's case — Eed and yellow softening — Treatment, . . . . . . Ill

CHAPTER VI. Cerebral Embolism

Definition — Symptoms — Causes — Multiple emboli — Brown hospital case — Diagnosis — Prognosis— Cerebral softening — Morbid anatomy and pathology — Virchow, Cohnheim and Schiitzenberger's observations — Partial cerebral anaemia and softening — Treatment, . • 116

CHAPTER VII. Cerebral Softening

Definition — Symptoms — Anaemia and red softening — Yellow and white softening — Variations of temperature — Mental debility — Paralysis — Headache 1 — Aphasia — Chronic softening — Causes — Diagnosis— Prognosis — Morbid anatomy and pathology — Treatment — General and special indications, . 121

CHAPTER VIII. Encephalitis

Definition — Symptoms — Symptoms in the aged — When complicated with meningitis — Cerebral abscess — Causes — Diagnosis — Prognosis — Morbid anatomy and pathology — Treatment, 130

CHAPTER IX. Cerebral Hypertrophy

Definition — Symptoms — Causes — Diagnosis — Prognosis — Morbid anatomy and pathology — Treatment, 137

CHAPTER X. Cerebral Atrophy

Definition — Symptoms — Partial atrophy — General atrophy — Causes — Diagnosis — Prognosis — Morbid anatomy and pathology — Treatment — Electricity, 139

CHAPTER XL Primary Multiple Sclerosis.

Definition — Charcot's researches — Symptoms — Sclerosis limited to the hemispheres — Muscular incoordination — Causes — Diagnosis — Paralysis agitans and chorea — Prognosis — Morbid anatomy — Pathology — Secondary multiple sclerosis — Treatment, 143

CHAPTER XV. Cerebral Tumors

Varieties— Glioma — Psammoma— Cholesteatoma — Xeuroma— Cancer of the brain

— Tuberculous and syphilitic tumors — Mucous, lipomatous, cystic, and mel-

anoid tumors — Symptoms — Causes — Diagnosis — Prognosis — Morbid anatomy

and pathology — Aneurismal tumors — Treatment— General indications, 157

CHAPTER XVI. Cerebral Syphilis

Xature — Varieties — Symptoms — Congestive, vascular, and syphilomatous forms — Causes — Diagnosis — Syphilitic thrombosis — Prognosis — Morbid anatomy and pathology — Treatment, 164

SECTION II.

Meningeal Affections.

CHAPTER I. Simple Acute Meningitis

Lepto-meningitis cerebralis — Symptoms — Morbid anatomy — Pathology — Causes — Diagnosis — Prognosis — Treatment — General indications — Special indications, 171

CHAPTER II. Tubercular Meningitis

Definition — Leptomeningitis — Symptoms — Prodromic stage — Symptoms of excitement — Symptoms of depression — Closing stage — Morbid anatomy — Pathology — Etiology — Diagnosis — Tache cerebrale — Prognosis — Treatment — General and special indications, 179

CHAPTER III. Traumatic Meningitis

Forms — 1. Pachymeningitis — Symptoms — Treatment — 2. Arachnitis — Morbid anatomy — Symptoms — Etiology — Diagnosis — Prognosis — Treatment — 3. Leptomeningitis — Symptoms — Morbid anatomy - — Pathology — Complication — Prognosis — Treatment, . • . . 189

CHAPTER IV. Chronic Meningitis

1. Chronic convexital meningitis — Symptoms — Morbid anatomy and pathology —

Causes — Diagnosis — Prognosis — Treatment — 2. Chronic basilar meningitis —

Symptoms — Morbid anatomy — Pathology — Causes — Diagnosis— Prognosis —

Treatment— General and special indications, 195

CHAPTER II. Vertigo

Definition — Muscular coordination — Etiology and pathology — Varieties — 1. Labyrinthine or auditory vertigo — Symptoms — Diagnosis — Prognosis — 2. Ocular vertigo — Symptoms — 3. Gastric vertigo — Symptoms — Diagnosis — 4. Nervous vertigo — Symptoms —5. Intracranial vertigo — Diagnosis — Treatment — General and special indications, 269

CHAPTER III. Insomnia

Sleep — Sopor — Partial insomnia — Complete insomnia — Causes — Treatment — General indications — Special indications, ..... 282

CHAPTER IV. Coma

Definition — Degrees of insensibility — Carus — Diagnosis — Causes — Prognosis — Treatment — Special indications, 286

s, CHAPTER V.

Sunstroke.

Varieties — 1. Syncop a/— Symptoms — 2. Asphyxial — Symptoms — 3. Hyperpyrexial — Symptoms — Vaso-motor paralysis and rise in temperature — Morbid anatomy — Causes — Prognosis — Treatment — General and special indications, 290

Chapter I. Functions Of The Cerebrum

Although numerous experimental researches had been previously made with a view to determine the special functions of different parts of the brain, it was not until the year 1870 that the cortical portion was found to be endowed with either sensibility or motor excitability; previous observations tending to show that neither pain nor convulsive action could be produced by stimulation or lesion of any portion of either the grey or white matter of the hemispheres. In that year, however, two German physiologists, Fritsch and Hitzig, by subjecting certain parts of the cerebral cortex of a dog to a weak galvanic current, discovered certain centres of motion in the grey matter of the hemispheres, which, when thus stimulated, could be made to produce certain well-defined muscular movements. These physiologists, by applying electricity to different portions of the cerebral surface, showed (1) that the grey matter of the hemispheres can be directly stimulated ; (2) that there are true motor centres in the cerebral cortex; (3) that the action on the muscular system is a cross-action, that is, that it acts only on the side opposite the seat of irritation; (4) that there are special centres or areas governing the movements of the extremities, the jaws, and the tongue; (5) that the special function of each area is limited to its particular centre, except so far as it may be affected by vicarious action ; and (6) that severe hemorrhage destroys the excitability of the grey matter of the cortex; thus accounting, perhaps, for the negative results reached by previous investigators. According to the same authorities, the motor centres, even when contiguous to each other, or occupying the same convolution, may be connected with w y ide]y different sets of muscles. Thus, the centre governing the supinator and flexor muscles of the forearm is found to be in close relation with the centre controlling the zygomatic muscles of the face, w T hilst adjoining the latter is a centre affecting the movements of the eyes and head. These results were afterwards confirmed by Ferrier, who repeated the experiments on the brain of a monkey, an animal whose cerebral convolutions most nearly resemble those of man.

The following is a brief summary of the results obtained by these observers, so far as they bear upon the theory of cerebral localization:

1. Notwithstanding the fact that, as shown by previous investigators, the hemispheres fail to respond to any form of mechanical, chemical or thermal lesion or stimulation, this is found not to be the case with electrical stimulation, the direct application of which to the surface of the hemispheres, in certain regions, causing definite movements in certain remote parts of the body; and, what is still more important, these movements are found to be associated with irritation of certain circumscribed areas.

2. While considerable differences exist between Hitzig and Ferrier in regard to the extent of cerebral localization, as well as in respect to the character and significance of the phenomena elicited by their experiments, the discrepancies between them may be satisfactorily accounted for, partly by the manner in which they interpret them, and partly by the difference in their methods of investigation.

3. The method employed by Hitzig consisted chiefly in applying directly to the surface of the hemispheres, by means of blunted electrodes, a galvanic current of sufficient intensity to cause a distinct sensation when applied to the tip of the tongue. Ferrier's method was by means of a similar application of the electrodes of an induced or secondary current, of a strength sufficient to cause a pungent, but quite bearable sensation when applied to the tongue, affording a greater degree of stimulation without danger of producing disorganization.

4. An electrical current that will cause intense and indefinite action in an animal non-narcotized, w T ill, according to Ferrier, excite only moderate and definite action in an animal merely rendered insensible to pain, and no effect whatever on one fully anaesthetized. The state of the cerebral circulation also greatly modifies its excitability, haemorrhage lowering it in a marked degree. Great differences also exist in different animals, with respect to the degree and duration of the excitability of the hemispheres. Again, various regions of the brain differ in respect to their excitability. Thus, a current sufficient to cause a decided contraction of the orbicularis oculi, will, according to this authority, fail to produce any movement of the limbs. By observing this principle, using the faradic current, and applying a current of sufficient strength to produce a uniformly definite effect, Ferrier obtained positive results in regions of the brain in which Fritsch and Hitzig, with the weaker galvanic current, failed to elicit symptoms, and which they therefore termed inexcitable.

5. The situation of the motor centres in man, according to the physiological experiments of Ferrier on the monkey, an animal whose brain, as already stated, most nearly resembles that of man, is as follows: (See Cut, page 20.)

a. The centres for the movements of the eyes are situated on the posterior half of the superior and middle frontal convolutions (12), and the anterior and posterior branches of the angular gyrus (13, 13'). Electrical stimulation of the former (12) causes elevation of ilie eyelids, dilatation of the pupils, conjugate deviation of the eyes, and turning of the head toward the op-

INTRACRANIAL DISEASES.

posite side. Stimulation of the posterior centres (13, 13') causes the eyes to move toward the opposite side, with an upward or downward deviation, according as the electrodes are on one or the other branches of the angular gyrus.

The connection of this region (the angular gyrus) with the organ of vision, has been noticed by Hitzig, Goltz, McKendrick and others, the first two of whom experimented upon dogs, and the latter upon pigeons. Ferrier objects to Goltz's method of research — which consisted in washing away a portion of the brain after trephining over the spot selected for investigation — as not fulfilling the conditions required in investigations

Diagram representing side view of the human brain. — (After Ferrier.)

of this nature. Ferrier's method of localized destruction of special areas, was chiefly by means of the actual cautery, varied occasionally with excision of the part. The result of his experiments upon this part was, that while electrical irritation of the angular gyrus, in which one of these motor centres for the eyes is situated (13, 13'), produces the movements of the eyes, pupils, and head above stated, its destruction causes no paralysis in the muscles of either the eye, its lids, or the pupils. Unilateral destruction of this centre, however, produces temporary blindness in the opposite eye; whilst bilateral destruction of this centre causes 'permanent blindness in both eyes. It is plain from this that the centre of each hemisphere has a peculiar effect upon both eyes, which is explained by the peculiar decussation of the optic nerves in the optic chiasm. It is also plain that, as stated by Ferrier, the movements consequent on electrical stimulation of this centre are merely reflex indications of sensory stimulation. Whether, as he says, these movements are ue to the associated action of lower centres, cannot be experimentally determined. We shall recur to this subject again, under the head of sensory centres (q. v.).

b. The centres for the movements of the jaws and tongue, are situated at the inferior extremity of the ascending frontal (Broca's) convolution, on a level with the posterior termination of the third frontal convolution (9 and 10). Electrical stimulation of this region is attended with opening of the mouth, and with protrusion (9) and retraction (10) of the tongue; action bilateral. These movements frequently continue after the electrodes are withdrawn. Ferrier found, in experimenting upon the dog, that the stimulation of this region also occasionally caused vocalization, or feeble attempts at barking or growling. In one experiment this was exhibited in a very striking manner. Each time the electrodes were applied to this region, the animal uttered a loud and distinct bark. To exclude the possibility of mere coincidence, Ferrier says he then stimulated in succession various parts of the exposed hemisphere, producing the characteristic reaction of each centre, but no barking. We shall see hereafter that Broca's convolution is, in man, the seat of intelligent language, and this experiment seems to confirm the truth of Broca's discovery, so far as experiments on the lower animals could be expected to do it.

c. The centres for the mouth and lips are situated on the ascending frontal convolution, above the centres for the jaws and tongue (7 and 8). Electrical irritation of the upper portion of this region (7), by its connection with the zygomatic muscles, retracts and elevates the angle of the mouth; whilst stimulation of the lower portion (8) elevates the ala of the nose and upper lip and depresses the lower lip, so as to expose the canine teeth on the opposite side.

.d The movements of the upper extremity are so numerous

INTRACRANIAL DISEASES.

and complicated, as to require many individual centres. That for supination and flexion of the forearm, is situated on the upper part of the ascending frontal convolution (6); that for extension and forward movement of the arm and hand, is situated at the posterior extremity of the superior frontal convolution (5); and the centre for backward movement of the arm with abduction, the palm of the hand being directed backward, as in swinging, occupies adjacent margins of the ascending frontal and ascending parietal convolutions (4). Centres for the extensors and flexors of the individual digits could not be differentiated, but the prehensile movements of the opposite hand are centralized in the ascending parietal convolution (a, b, c, d), the stimulation of which causes individual and combined movements of the fingers and wrists, ending in clenching of the fist. Paralysis caused by destruction of these centres, when the injury is limited to the cortical grey matter of the region included in them, is confined strictly to the voluntary movements produced by electrical stimulation of these particular centres, and without affecting the sensibility of the parts over whose movements they preside.

e. The centres for the movements of the lower extremity are situated on the posterior parietal lobule (1), and on the upper part of the ascending parietal and adjoining part of the ascending frontal convolution (2). The first of these centres (1) when electrically excited, advances the lower or opposite hind limb, as in walking. Occasionally this movement is confined to the foot and ankle, the foot being flexed on the ankle and the toes widely separated. Stimulation of the other centre (2) produces complex movements of the thigh, leg, and foot, with adapted movements of the trunk, by which the foot is brought to the median line of the body, as in scratching the chest or abdomen. Destruction of these centres, as in the case of those governing the movements of the upper extremity, causes paralysis of voluntary motion, without affecting the sensibility, the paralysis being confined to the movements resulting from electrical stimulation of these centres.

6. Whilst the great majority of physiologists, including Fritsch, Hitzig, Ferrier and other distinguished investigators, regard the above-described centres as directly motor, other noted observers, as Eckhard, Schiff, Hermann, and Brown- S'-quard, attribute the movements excited by electrical stimulation of the cerebral surface to a reflex, indirect, or vicarious action; and that, too, notwithstanding the fact that the results obtained by Hitzig and Ferrier are found to agree in most instances with clinical and pathological observation, as we shall see when we come to treat of the localization of cerebral diseases. Some contend that the movements observed are not due to the excitation of the cerebral cortex, but to the transmission of irritation to the motor ganglia below; in proof of which they point to the fact that Eckhard has succeeded in tracing one of the excitable fibres for the front leg from the cineritious substance down to the corpus striatum. MM. Lussana and Lemoigne, who also deny that the so-called cortical centres are true motor centres, found their objection upon the fact that. mechanical stimulation does not excite them, and that galvanism and faradism are also generally insufficient when the animal is fully anaesthetised, as well as immediately after death. They also point to the discovery of Goltz, who, in his experiments upon the dog, found that the motor paralysis observed after destruction of the cortical centres, is neither complete nor permanent, like that which follows the destruction of the lower motor centres. Hence we find Dr. Brown- Sequard, the most noted skeptic on this subject, using the following language: "Take, for instance, the sense of volition; we find it destroyed or altered in diseases of the brain, yet cases are not wanting in which certain parts of the brain have been destroyed while volition was not lost; and this is true of all the functions referred to the brain. At times alteration or destruction of these functions attend lesions of the brain, at times again these lesions are present while the symptoms are absent, and at times an entirely different class of symptoms ma)' appear. Each alleged function of the brain may remain after the destruction of what is considered its centre"* Brown-Sequard also denies the doctrine of cross-paralysis, basing his opinion on the histories of less than three hundred cases in which paralysis occurred on the same side as the cerebral lesion. But as he had to ransack the entire literature of medicine to

* Lecture delivered at the Cincinnati Hospital, March 13th, 1872.

find these exceptions to the general rule, that the paralysis is on the side opposite to the injury, and as many of these cases were very old, and therefore probably incorrectly reported, his opinion on this point, as on that of the cortical motor centres generally, is diametrically opposed to that of most of his colleagues. Moreover, from what Ave now know regarding the variations in the course of the pyramidal fibres, such exceptional cases are perfectly consistent with the received rule on this subject.

7. The advocates of the cortical theory of localization rely for the support of their doctrine chiefly on the fact, that paralysis of voluntary motion generally follows destruction of the corresponding cortical centres, and that any apparent exception to this result is capable of explanation in a way consistent with their view. They allege, also, that the theory derives marked support, not only from clinical observations, but from anatomical and pathological considerations. They refer with emphasis to the researches of Betz, who found in the region anterior to the fissure of Rolando, corresponding to Hitzig's motor centres, giant-pyramidal cells, while in the region posterior to that fissure, which is not excitable, layers of nuclei predominate. Xow these "giant-pyramids," which occur only in Hitzig's excitable zone, are not fully developed until after birth. Here, then, it is claimed, we have a striking analogy, so far as the nervous elements are concerned, to the motor elements in the grey matter of the spinal cord.

As for the transient character of the paralysis observed after destruction of cortical motor centres, it should be remembered that it applies only to quadrupeds ; in man and the monkey the paralysis is permanent. In view of this fact, Ferrier pertinently asks : " If we were to say, with Hermann, that the recovery in dogs disproves the view of the motor functions of the cortex, how shall we account for the paralysis observed in man and monkeys?" The explanation usually given of the phenomena, as met with in quadrupeds, is, that a process of compensation is effected by another portion of the cortex taking on the function of that which has been lost. In the case of bilateral movements, it is only necessary to assume a vicarious action of the corresponding centre of the opposite hemisphere. That such compensatory or vicarious action does take place where muscles of the opposite sides are usually associated in action, as in the movements of the eyes, chest, abdomen, etc., is evident, and seems to be satisfactorily explained by the theory of Dr. Broadbent, whose explanation is as follows : "Where the muscles of the corresponding parts on the opposite sides of the body constantly act in concert, and act independently, either not at all or with difficulty, the nerve-nuclei of these muscles are so connected by commissural fibres, as to be pro tanto a single nucleus. This combined nucleus will have a set of fibres from each corpus striatum, and will usually be called into action by both, but it will be capable of being excited by either singly, more or less completely according as the commissural connection between the two halves is more or less perfect. According to this hypothesis, then, if the centre of volitional action of one side is destroyed, or one channel of motor power cut across, the other will transmit an impulse to the common centre, and this will be communicated to the nerves of the two sides equally, if the fusion of the two nuclei is complete, and there will be no paralysis — more or less imperfectly to the nerve of the affected side if the transverse communication between it and its fellow is not so perfect, in which case there will be a corresponding degree of paralysis."

The above theory, which is in complete harmony with the facts of clinical experience, not only accounts for the comparative escape of bilaterally associated movements in case of corpus striatum haemorrhage, which the theory was formed to explain, but serves also to clear up the transient nature of the paralysis resulting from destruction of the cortical centres in quadrupeds, the movements of which are more generally automatic than are those of man and the monkey. This explanation, however, is not quite satisfactory, since, after recovering from paralysis caused by the extirpation of one cortical motor centre, the destruction of the corresponding centre of the opposite hemisphere does not reinduce the paralysis from which the animal had previously recovered. Besides, even after the destruction of both cortical centres, the power of voluntary movement of the parts to which their influence seems to be distributed is not entirely abolished. To account for these phenomena, Carville and Duret adopt the hypothesis of Flourens, Longet, and others, namely, that other portions of the hemispheres gradually assume the functions of the parts which have been destroyed. This law of functional substitution, however, is in direct conflict, not only with the doctrine of cortical localization of function, but with the results of the experiments on which that doctrine is founded. The law of substitution, in order to be consistent with the theory of cortical localization, requires to be limited to those centres of action already established — the lower ganglia — which, without resuming new functions, may in an indirect manner compensate for the loss of the upper centres.

THE SENSORY CENTRES.

7. We are indebted to Ferrier for most of our knowledge of the sensory centres of the cerebrum. We have already given the result of his experimental researches into that portion of the temporo-sphenoidal lobe known as the angular gyrus, in which is situated one of the motor centres controlling the movements of the eyes, pupils, and head, but w T hose destruction, while it produces no motor paralysis in the muscles of either the eye, the eyelids or the pupil (showing it to be not a direct but only a reflex motor centre), causes loss of vision in the opposite eye (which, however, is not permanent if the opposite gyrus remains sound), and when both angular gyri are destroyed, causes blindness of both eyes, which is complete and permanent, thus proving it to be a true sensory centre.

b. Pursuing his investigations, Ferrier found in the superior temporo-sphenoidal convolution a centre (14) which, under faradic irritation, caused the monkey operated upon to suddenly retract or prick up the opposite car, widely open the eyes, dilate the pupils, and turn the head and eyes to the opposite side — phenomena which a loud sound made in the ear opposite the irritated hemisphere would be likely to produce. This inference, as to the nature of the effect produced by electrical stimulation of this centre, was confirmed by destruction of the convolution, which, as in the case of the visual centre, caused apparent deafness on the opposite side, and, when both sides were de-