Brain surgery

Preface

Brain surgery is at present a subject both novel and interesting. It is within the past five years only that operations for the rehef of epilepsy and of imbecility, for the removal of clots from the brain, for the opening of abscesses, for the excision of tumors, and for the relief of intracranial pressure have been generally attempted. These operations are the practical outcome of the acceptance of the facts of localization of brain function established by the combined labor of physiologists, clinical observers, and pathologists.

Brain surgery has as its essential basis the accurate diagnosis of cerebral lesions, which was impossible until the localization of cerebral functions had been determined. And this diagnosis must be made by the physician before the surgeon is called in to remove the disease.

It is the object of this book to state clearly those facts regarding the essential features of brain disease which will enable the reader to determine in any caseboth the nature and the situation of the pathological process in progress, to settle the question whether the disease can be removed b}" surgical interference, and

IV

PREFACE.

to estimate the safety and probability of success by operation.

The facts have been reached by a careful study of the literature of the subject and by a considerable personal experience. The number of articles written upon brain surgery, the number of cases recorded and of operations reported in this country and in Europe during the past ten years is enormous. This literature is accessible to those only who have a large medical library at their command and who have the time for literary research. I have undertaken to bring together and to sift the scattered facts, to arrange them in an orderly sequence, and to deduce such conclusions from their analysis as seem warranted by critical study. While in no way disregarding the work of foreign observers, I have endeavored to utilize American observations and to cite American cases in preference to others. And this has in no way hampered me, for it is to the industry and genius of American surgeons that much of the great advance in this department of surgery is due.

To this collection of facts I am able to contribute a considerable number of cases of cerebral disease, operated upon under my direction. My own experience in the clinical study of brain diseases and my observation of the method and results of operations performed by different surgeons have enabled me to estimate the statements of other writers with some degree of critical judgment, and to arrive at certain convictions of my own.

PREFACE. V

I have to express my deep obligation to Dr. McBurne}' for placing at my entire disposal the large number of cases in which he has operated for me, and for a revision of the chapter upon the operation of trephining ; and also my thanks to Drs. Weir, Hartley, Poore, and Briddon for permission to cite the cases which I have seen with them. I am indebted to Dr. Van Gieson for the very careful investigation of pathological material placed in his hands and for the drawings which illustrate his descriptions.

It is my hope that this work may aid the physician to diagnosticate brain diseases with more accuracy, and to select such cases as are properly open to surgical treatment by trephining; and also that it may enable the surgeon to perform his delicate task with more precision and with a fuller knowledge of those principles of local diagnosis v/hich should form his constant guide.

M. Allen Starr.

No. 22 West 48th Street, New York, March 27th, 1893.

CHAPTER I. The Diagnosis of Cerebral Disease

PAGE

Diagnosis is Preliminary to Operation and must be Made by the Physician before Surgical Treatment is Attempted. The Diagnosis of the Nature of the Cerebral Lesion. The Diagnosis of the Situation of the Cerebral Lesion. The Facts of Localization Essential to Diagnosis. Cranio- Cerebral Topography, . . . 1

CHAPTER II. Trephining for Epilepsy

The Varieties of Epilepsy. Jacksonian Epilepsy. The Motor Form of Attack. The Sensory Form of Attack. The Aphasic Form of Attack. The Psychical Form of Attack. Traumatic Epilepsy. The Operation for Epilepsy. Records of Cases of Epilepsy operated upon, Personal and Selected. The Pathology of Jacksonian and Traumatic Epilepsy. The Results of Trephining for Epilepsy. Conclusion, . . .19

CHAPTER III. Trephining for Imbecility Due to Microcephalus

Clinical Types of Microcephalic Children : (1) Paralytic Cases ; (2) Imbeciles ; (3) Cases of Sensory Defect. The Occurrence of Epilepsy in these Children. The Pathology of these Clinical Types. The Operation of Craniotomy and its Results. Table of Cases. Report of Personal Cases. Conclusions, ........... 114

Vlll CONTENTS.

CHAPTER IV. Trephining for Cerebral Hemorrhage

PAGE

Records of Cases of Clots Removed from tlie Brain. Report of Personal and Selected Cases. The Symptoms of Traumatic Cerebral Hemorrhage. The Differential Diagnosis Between Intra-Dural and Extra-Dural Hemorrhage. Operations for Non- Traumatic Hemorrhage, 157

CHAPTER V. Trephining for Abscess of the Brain

The Surgical Treatment of Brain Abscess. The Varieties of Brain Abscess. (1) Traumatic Abscesses. Surgical Indications for Trephining, General and Local. Report of Cases. (2) Abscesses Secondary to Ear Disease. Symptoms. Differential Diagnosis between Abscess, Meningitis, and Sinus Thrombosis. The Situation for Trephining after Ear Disease. Illustrative Cases. Conclusions 179

CHAPTER VI. Trephining for Tumor of the Brain

The Frequency and Varieties of Tumors in the Brain. Analysis of Six Hundred Tumors. Tumors in Children Contrasted with Tumors in Adults. The Diagnosis of the Nature of the Tumor. The Diagnosis of the Situation of the Tumor. The Percentage of Brain Tumors Open to Operation. The Results of Operation for Brain Tumors. Analysis of Ninety-seven Cases. I. Cerebral Tumors. Selected American Cases. Personal Case. Tumor of Frontal Lobes. 11. Cerebellar Tumors. Diagnosis. Difficulties of Operation. Three Personal Cases. Table of all Brain Tumors Operated upon. Conclusions, .......... 200

Trephining for Headache, and Other Conditions, . 273

CHAPTER X. The Operation of Trephining

The Necessity of Antiseptic Precautions. The Preparation of the Patient. The Choice of an Anaesthetic. Marking the Scalp. The Incision in the Scalp. Methods of Opening the Skull. The Treatment of Hemorrhage. Opening of the Dura. The Exploration of the Brain. The Closure of the Wound 275

LIST OF ILLUSTRATIONS.

FIG. PAGE

1. Diagram of the Functional Areas of the Right Hemisphere, 4

2. Diagram of the Functional Areas of the Left Hemisphere, . 5

3. Diagram of the Median Surface of the Right Hemisphere, . 7

4. The Projection Tracts within the Brain, .... 9

5. The Association Tracts within the Brain, . . . .10

6. Photograph of the Head and Brain (Fraser) , ... 12

7. Photograph of a Cast of the Head, 13

8. Diagram of the Cranial Measurements to Locate the Fissures, 14

9. Diagram of the Relations of the Skall and the Brain (Reid) , 15

10. Diagram to Show the Relation of the Skull and the Func-

tional Areas of the Right Hemisphere, . . . .16

11. Diagram to Show the Relation of the Skull and the Func-

tional Areas of the Left Hemisphere, . . . .17

12. Diagram to Show the Opening in the Skull in Case I. , . 30

13. Diagram to Show the Opening in the Skull in Case II., . 32

14. Diagram to Show the Opening in the Skull in Case III. , . 36

15. Diagram to Show the Opening in the Skull in Case IV. , . 37

16. Diagram to Show the Opening in the Skull in Case V. , .39

17. Diagram to Show the Opening in the Skull in Case VI. , . 42

18. Diagram to Show the Opening in the Skull in Case VII. , . 43

19. Diagram to Show the Opening in the Skull in Case VIII. , . 45

20. Diagram to Show the Opening in the Skull in Case IX. , . 47

21. Diagram to Show the Opening in the Skull in Case X., .48

22. Diagram to Show the Opening in the Skull in Case XL, . 50

23. Diagram to Show the Opening in the Skull in Case XII., . 53

24. Diagram to Show the Opening in the Skull in Case XIII. , . 54

25. Section through Pia and Cortex Showing Meningitis, . . 71

26. Section Showing Spiculum of Bone in the Brain in Case III. , 84

27. Degeneration of Brain Cells in Epilepsy, . . . .87

28. Degeneration of Brain Cells in Epilepsy, . . . .89

29. Degeneration of Brain Cells in Epilepsy, . . . .90

30. Changes in the Neuroglia in Epilepsy, . . . . .98

31. Changes in the Neuroglia in Epilepsy, ..... 99

32. Neuroglia Cells Undergoing Changes in Epilepsy, . . 100

Xll

LIST OF ILLUSTRATIONS.

FIG.

33. Adhesion of Scalp and Cortex in Case II. , .

34. Section Sliowing Changes in Membranes and Brain in Case

II.,

35. Clianges in the Cortex in Case II. ,

36. The Capillaries and the Neuroglia in Case II. ,

37. The Neuroglia in Case II. , .

38. Porencephalic Brain (Shattenberg) ,

39. Porencephalic Brain (Ferraro) , . . .

40. Porencephalic Brain (Ferraro) , . . .

41. Hemiatrophy of the Brain, Superior Surface,

42. Hemiatropliy of the Brain, Inferior Surface,

43. Hydrocephalus (Delafield and Prudden) ,

44. Diagram to Show the Opening in the Skull in Case XIV. , .

45. Diagram to Show the Opening in the Skull in Case XV. , .

46. Diagram to Show the Opening in the Skull in Case XVI. , .

47. Diagram to Show the Opening in the Skull in Case XVII. , .

48. Diagram to Show the Opening in the Skull in Case XVIII. , .

49. Diagram to Show the Situation of the Clot in Case XVIII. , .

50. Diagram to Show Relation of Skull and Functional Areas of

the Left Hemisphere, . . . . . . , ,

51. Diagram to Show the Opening in the Skull in Case XIX. , .

52. Diagram to Show the Opening in the Skull in Case XX. ,

53. Photograph of the Brain Abscess in Case XX. , . . .

54. Lateral Aspect of the Skull with Trephine Openings (Bal-

lance),

55. The Cerebral Axis (Allan Thompson),

56. Photograph of the Skull and Brain (Fraser) , . . .

57. Diagram to Show the Opening in the Skull in Case XXI. , .

58. Photograph of a Tumor Removed from the Brain in Case

XXI

59. Hydrocephalus (Delafield and Prudden) , ....

170 175 186

193 210 211 234

Chapter I. The Diagnosis Of Cerebral Disease

Diagnosis is Preliminary to Operation and must be Made by the Physician before Surgical Treatment is Attempted. The Diagnosis of the Nature of the Cerebral Lesion. The Diagnosis of the Situation of the Cerebral Lesion. The Facts of Localization Essential to Diagnosis. Cranio- Cerebral Topography.

There are two essential preliminaries to any operation upon the brain. The first is the diagnosis of the nature of disease which is present, and the second is the diagnosis of its situation. Both are purely medical questions, and until they are decided the surgeon cannot be asked to operate.

The diagnosis of the nature of disease in the brain is usually one of no great difficulty. The general cerebral symptoms characteristic of meningitis, either of the dura mater or of the pia mater, of hydrocephalus, of cerebral hemorrhage, of cerebral softening from embolism or thrombosis, of cerebral abscess, of cerebral tumor, and of sclerosis of the brain are in the majority of cases quite evident. The differential diagnosis between these conditions is elaborately discussed in every text-book on practice and on neurology. A careful study of the various symptoms, of the order and manner of their development, and of the general history of the case will usually lead with little difficulty to a diagnosis of the nature of the lesion present.

It is not my purpose to enter upon the discussion of the diagnosis of cerebral disease in general. In the course of the following chapters and in the recital of certain cases the essential facts will be carefully considered. But it should not be forgotten that surgical interference is by no means warranted in any case unless the nature of the disease is well determined.

The second essential preliminary to operation is a knowledge of those facts regarding the localization of brain functions, so far as they are at present determined, which may lead to a correct diagnosis of the situation of the disease. These facts may be stated briefly.

The Fads of Localization.

There are certain areas upon the cortex of the brain, not necessarily co-extensive with either lobes or convolutions, whose functions are accurately known.

These areas are : (1) the sensori-motor area. (2) The speech areas. (3) The visual area. {-^) The auditory area. (5) The area of sensations of smell and of taste.

(1) The sensori-motor area (Figs. 1 and 2) includes the cortex of the anterior and posterior central convolutions which border the fissure of Eolando and the adjacent cortex in front and behind these convolutions.

Each hemisphere controls movement on the opposite side of the body, but as the right hand is more generally used and is better trained than the left, this area is larger on the left hemisphere than on the right.

The cortex of the posterior part of the second frontal convolution controls the movements of the eyes and head. Impulses starting from this area produce conjugate movement of these parts toward the opposite side. The eye district is below, the head district above.

The lower third of the anterior and posterior central convolutions governs the movements of the face, tongue, larynx, and pharynx. The eyebrows and cheeks are controlled by the upper and forward part of this area; the tongue and larynx by the lower and forward part ; the mouth, pharynx, and platysma by the hinder part.

The middle third of the anterior and posterior central convolutions governs the movements of the upper extremity ; the shoulder motions being controlled in the anterior and upper part of this area, the elbow motions in its middle part, and the hand and finger motions in its posterior and lower part.

The upper third of the anterior and posterior central convolutions including their junction in the paracentral lobule controls the motions of the lower extremity ; the thigh, knee, foot, and toes being governed by various parts of this area from before backward in the order nam^ed.

It will be noticed that the parts susceptible of the finest and most delicate movements, those directed by the most acute sensations, the lips, the fingers, and the toes, lie furthest back in the motor area, chiefly in the posterior central convolution. Lesions in this convolution almost always cause some loss of tactile sensation as well as paralysis, and hence this area is thought to be the seat of tactile sensations as well as of movements, while some cases point to the localiza-

FiG. 1.— Diagram (after Eberstaller) of the Fissures and Convolutions of the Convexity of the Right Hemisphere of the Brain. The relative depth of the fissures is indicated by the shading. The extent of the fimctional areas is indicated by the dotted lines.

tion of muscular sensations in the area just behind that of motion.

The median surface of the hemisphere in front of the paracentral lobule is known to be related to movements of the trunk in monkeys, but these movements are rarely affected by disease in man and their cortical representation is still uncertain, though

THE DIAGNOSIS OF CEREBRAL DISEASE.

a case reported by Horsley ' points to the cortex in front of the leg area on the convexity as the probable location of the trunk area.

There are no sharply defined sections of the motor area to be assigned to special motions. Each motion, each part of a limb, has a wide general representation over the cortex and a special representation at a limited area. Horsley says that the areas of representa-

FiG. 2.— Diagram of the Fissures and Convolutions of the Convexity of the Left Hemisphere of the Brain. The speech areas are shown on this hemisphere. The motor area is more extensive than on the right hemisphere.

tion of different limbs merge into one another ; thus in the representation of the thumb we find that there is a focus, but that the thumb is represented over a great deal of the upper limb region, and that this representation diminishes in intensity gradually as we pass from the focus upward. This explains the fact that the excision of a small area does not totally para- ^ Amer. Jour. Med. Sci., April, 1887, Case III., Fig. 18.

\ lyze the portion of the limb represented chiefly on

I that area. The adjacent areas represent to some ex-

f tent that limb and hence can govern it if need be.

j (2) TJie speech areas (Fig. 2) are of four kinds and

in four locations. They are limited to the left hemisphere in right-handed persons and to the right hemisphere in left-handed persons. There is the motor speech area in the posterior part of the third frontal convolution, in which the movements concerned in the |. act of speaking are controlled. The use of language

and the power of talking are affected when this region is destroyed. There is the audit ory speech area in the first and second temporal convolutions, in which the memories of word sounds are stored up. The understanding of language and the powder of recollecting the names of objects are lost when this region is destroyed. There is the visual speech area in the lower parietal region, in which the memories of printed words are stored up. The understanding of written language and the power to read are lost when this region is destroyed. The poicer of writing is a part of speech and is usually lost when the motor speech area is destroyed, but its exact location is not fully determined; some cases pointing to the second frontal convolution, others to the lower parietal convolution near the hand centre as its probable cortical position.

(3) The area of sensations of sight (Fig. 3) is located in the occipital lobe of the brain, including the cuneus on the median surface and the occipital convolutions on the convexity. The cortex lying in the calcarine fissure is the part primarily reached by the visual impulses, ' but the parts named are also concerned in vision. Each occipital lobe receives impressions from one-half of both eyes, hence a lesion in one lobe produces hemianopsia, a half -blindness in both eyes,

Fig. 3. —The Median Surface of the Right Hemisphere (after Ecker). The visual centre is in the cortex lying within the calcarine fissure, OC, and in the cuneus, OZ. The sensations of smell and taste are received in the uncinate convolution, [7, and at the tip of the temporo-sphenoidal lobe. AB shows the position of the paracentral lobule, which is included in the motor area of the leg.

the blind field of vision being on the opposite side to the lesion.

(4) The area of sensations of sound (Fig. 2) is located in the first and second temporal convolutions of the brain. Each ear is connected with, both hemispheres ; hence deafness from a unilateral lesion is only partial and is not generally noticed. But if both temporal lobes are destroyed the patient becomes totally deaf.

^ Henschen: " Pathologic des Gehirns, " ii. , 358, 1892.

(5) The area of sensations of smell and taste (Fig. 3) is located at the tip of the temporal lohe on its under and inner surface, which rests on the sphenoid bone. Each lobe is related to sensory organs on both sides, and a unilateral lesion does not often produce noticeable symptoms.

There are large areas of the cortex of the brain whose function is undetermined. These are much more extensive on the right hemisphere than on the left. There are no definite symptoms produced, so far as we now know, by lesions in these areas ; but the negative fact is certain, that lesions in them do not cause disturbances of motion, of sensation, or of speech.

There appears to be a certain relation between the frontal lobes of the brain and the higher forms of intellectual activity, the powers of fixing the attention and of reasoning and of self-control. But disease here does not cause a loss of any one mental faculty, and for the higher powers of the mind a general integrity of the entire brain, not of any one part, is necessary. When it is considered that every concept is made up of numerous memory pictures joined together, each of which has a separate location in the brain cortex, it becomes evident that to the process of thought a healthy state of the entire cortex is necessary and also of the white matter beneath it, through which the associating fibres pass. And it is therefore impossible for a single lesion anywhere to cause a loss of memory or of imagination or of judgment. Yet for the co-ordination of facts into orderly series, for comparison, and for analysis of knowledge gained through the senses, the healthy state of the frontal lobes appears to be necessary. And lesions in

Fig. 4.— The Projection Tracts joining the Cortex with Lower Nerve Centres. Sagittal section showing the arrangement of tracts in the internal capsule. A, Tract from the frontal lobe to the pons, thence to the cerebellar hemisphere of the opposite side; ^, motor tract from the central convolutions to the facial nucleus in the pons and to the spinal cord ; its decussation is indicated at K; C, sensory tract from posterior columns of the cord, through the posterior part of the medulla, pons, crus, and capsule to the parietal lobe; jD, visual tract from the optic thalamus (OT) to the occipital lobe; E, auditory tract from the inter-geniculate body (to which a tract passes from the viii. n. nucleus (J) to the temporal lobe; F, superior cerebellar peduncle; (t, middle cerebellar peduncle; H, inferior cerebellar peduncle; CiV, caudate nucleus; CQ, corpora quadrigemina; Fit, fourth ventricle. The numerals refer to the cranial nerves.

the frontal region, especially upon the left side, are quite uniformly attended by mental dulness, apathy, lack of power of concentration, and imperfect self-control.

BRAIN SURGERY.

The cortex of the hemispheres upon the base of the bram lying on the orbital plate, on the sphenoid and temporal bones, and on the tentorium cerebelli has as yet no assignable functions, and lesions in these regions do not produce recognizable symptoms.

As to the functions of the centrum ovale, it is known

Fig. 5.— The Association Fibres in the Centrum Ovale. A, Between adjacent convolutions; 5, between frontal and occipital lobes; C, between frontal and temporal lobes, the cingulum; D, between temporal and frontal lobes— lesion of this tract causes paraphasia; E, between occipital and temporal lobes— lesion of this tract causes word-blindness ; CA^, caudate nucleus; OT, optic thalamus.

that through this region the great brain tracts pass in various directions (Fig. 4) . Many of these connect the various areas of the cortex with their respective sensory or motor mechanisms in the base of the brain and spinal cord. Others join the different areas of the cortex with each other, this bringing about a combination of sensory impressions into a single mental image (Fig. 5). Others again unite the two hemispheres of the brain with one another, it being certain that symmetrical areas must act in unison on the two sides.

The basal gangha, the corpora striata, and optic thalami, lying deep within the hemispheres, are masses of gray matter whose function is undetermined. Lesions in them frequently affect the various tracts which pass between them in the internal capsule, thus cutting off afferent or efferent impulses to and from the cortex and causing sensory and motor symptoms of the nature of hemiansesthesia, hemianopsia, and hemiplegia (Fig. -1). But if disease in the ganglia does not invade the internal capsule it cannot be detected during life.

The crura cerebri, pons, and medulla contain the centres of the various cranial nerve nuclei, and hence cranial nerve palsies are caused by disease in them. They transmit motor and sensory tracts to the spinal cord, hence numerous symptoms appear when they are injured.'

The cerebellum, lying in the posterior cranial fossa beneath the tentorium cerebelli, controls the equilibrium of the body; hence disturbances of the nature of staggering and vertigo are produced by lesioDs affecting it, especially if its median lobe is involved.

These local symptoms of brain disease must form the chief guides to the physician in his diagnosis and

^ For a fuller statement of these facts of localization the reader is referred to my book, " Familiar Forms of Nervous Disease."

BRAIN SURGERY.

to the surgeon in operations. When they are present they point to a particular area of the organ which must be involved. When they are absent both neu-

FiG. 6.— Photograph (Fraser) Showing the Relations of the Cerebral Hemisphere, the Cerebellum, the Cranial Nerves, the Upper Spinal Cord and Cervical Nerves to the Surface of the Head. The figures 1, 2, 3, are placed upon the chief convolutions of the frontal, parietal, occipital, and temporal lobes of the hemisphere.

THE DIAGNOSIS OF CEREBRAL DISEASE.

rologist and surgeon are as helpless as they were before any of these facts of localization were determined.

Cases open to Operation.

There are many cases in which it is evident that brain disease is present, but in which it cannot be

Ftg. 7.— Photo^aphof a Cast of a Head showing the Relation of the Cranial Sutm-es to the Cerebral Fissures and Convolutions. F, Frontal ; P, parietal ; O, occipital ; T, temporal lobes ; S, fissiire of Sylvius ; R, fissure of Rolando ; /, interparietal fissTu-e ; P O, parieto-occipital fissure ; A P, anterior and posterior central convolutions.

located because the necessary symptoms to determine its location are absent.

BRAIN SURGERY.

There are other cases in which it is evident that the disease is located deep within the hemispheres or on the base of the brain entirely bevond the reach of the surgeon.

It is therefore evident that only in a limited number

{. distcnz

Occiv prctu,

Glabella

Fig. 8.— Diagram Showing the Measurements Required to Determine the Position of the Fissures of Rolando and Sylvius.

of cases of brain disease can any operative interference be considered with favor.

Operations may be performed for the relief of epilepsy, for the cure of imbecility, for the removal of clots, for the opening of abscesses, for the excision of tumors, for the relief of intracranial pressure— with or without drainage of the lateral ventricles — and for the cure of traumatic insanity. In the following

THE DIAGNOSIS OF CEREBRAL DISEASE.

chapters each of these conditions will be discussed, the pathology of the disease being especially considered, and the results of operations hitherto done being fully described.

Cixuiio- Cerebral Topography.

The fact that the brain may be exj^osed for the removal of diseased parts in appropriate cases has made

Fig. 9.— The Guiding Lines of Reid and the Relation of the Chief Convolutions

to them.

it necessary to ascertain the relation of its different fissures and convolutions to the cranial sutures, or to certain landmarks upon the surface of the head. These relations are well shown in the figure (Fig. Y), which is a photograph of a cast of a head made immediately after death by Dr. Cunningham, of Dublin.' Numer-

1 See Dublin Journ. Med. So., 1888, p. 157. For an opportunity of photographing this cast I am indebted to Dr. F. Ferguson, Curator of the Museum of the New York Hospital.

BRAIN SURGERY.

ous rules have been laid down for the determination of the location of various parts of the convex surface of the hemisphere upon the head. The most important are the following, which may he compared with the diagram (Fig. 8), and with Eeid's figures (Fig. 9).

Fig. 10.— The lines indicating the fissures of Rolando and Sylvius laid down on the skull according to the rules given in the text and the relative situation of the functional areas of the cortex to these lines : the right hemisphere.

To find the fissure of Eolando, lay down a line from the root of the nose to the occipital protuberance over the top of the head, and take a point 0.557 of the distance back upon this line. This point will correspond to the upper end of the fissure. The fissure makes an angle of 67° with the median line just

THE DIAGNOSIS OF CEREBRAL DISEASE.

measured. Hence if two strips of metal fixed to one another at this angle be placed on the head with their junction upon the upper end of the fissure, when one strip is on the median line the other strip, pointing forward and downward, must lie over the fissure of

Fig. 11.— The lines indicating the fissures of Rolando and Sylvius laid down on the skull according to the rules given in the text and the relative situation of the functional areas of the cortex to these lines: the left hemisphere.

Rolando. In its lower third the fissure becomes a little more vertical than the strip. The fissure is about three and a half inches long.

To find the fissure of Sylvius, lay down a base line from the lower margin of the orbit to the auditory meatus. Lay down a second line parallel to the base line from the external angular process of the frontal bone backward one inch and a quarter and then measure upward one quarter of an inch ; this gives point one. Find the most prominent part of the parietal eminence and from it draw a line downward perpendicular to the base line, and on this take a point three-quarters of an inch below the eminence ; this gives point two. Join these two points and the line will lie over the fissure of Sylvius. The anterior limb of the fissure will be two inches behind the external angular process. The fissure of Sylvius is about four inches long.