These structures are not confined to the circumscribed space covered by the inner tympanic wall, but extend well backward into the aditus, the semicircular canal lying behind, and the facial canal just below, that bony space. The tympanic portion of the aqueduct, presenting as a horizontal ridge just above the oval window, is certainly not the only region in which the nerve may be exposed to injury. The relation of the bend of the canal to the aditus and antrum is more intimate and surgically important than is generally recognized. This relation is very well shown in several of the writer's specimens presented to-night. (See Text-plates No. IV. and No. V.) When, therefore, we recall the statement of Broca, that if in the course of a mastoid operation the antrum is not reached at a depth of 20, 22, or 25 mm, the surgeon need not be afraid to go still farther, the importance of correcting so dangerous a dogma becomes obvious.

What we have spoken of as the triangle of election has been described by many writers as the surgical guide to the

antrum.

So far as we are justified in drawing any conclusions from the measurements presented and facts adduced, they may be stated as follows:

1. That in operations upon the mastoid process the antrum should always be approached from the nearest point upon the mastoid cortex, which in the great majority of bones is the small triangular space just behind the spine of Henle.

2. That this point of attack not only furnishes a guide to the site of the antrum, but also gives fairly accurate data as to the depth beyond which it is not safe to proceed.

3. That the depth of the antrum is always less than the length of the postero-superior wall of the meatus; that in the great majority of bones it is not over 12 mm, is often very much less, and is never greater than 15 mm, or § inch; and therefore

4. That in a surgical attempt to expose the antrum a depth of inch should be regarded as the extreme limit of safety.

N. B.-The original drawings for this paper were prepared

from the writer's specimens by Dr. H. J. Prentiss, of the University-Bellevue Medical College,-to whom the writer wishes particularly to express his thanks.

REFERENCES.

I. GRUBER'S Diseases of Ear, p. 437.

2. POLITZER'S Diseases of Ear, 3d edition, p. 513.

3. BUCK, Diseases of Ear, p. 436.

4. DENCH, Diseases of Ear, p. 438.

5. SCHWARTZE, quoted by Gruber. Loc. cit., p. 438. 6. BROCA, Surgical Anatomy of Ear, p. 9.

INTRADURAL AND LATER DOUBLE CEREBRAL ABSCESS COMPLICATING CHRONIC TYMPANIC SUPPURATION; OPERATIONS; CURE.

By B. ALEX. RANDALL, M.A., M.D., AND BARTON H. POTTS, M.D., PHILADELPHIA.

(With a Temperature Chart.)

F. K., aged four years, came to Dr. Potts in the dispensary of the Children's Hospital with a history of discharge from the left ear for two years. Two weeks before being seen, the discharge ceased and the child complained of pain about the left ear. One week before examination, a slight swelling appeared behind the ear and she complained of headache, most marked in the region of the temple. She had not retained food for two days and vomited under examination.

Examination showed some oedema behind the auricle, but no fluctuation; some tenderness over the mastoid; upper and posterior canal-wall red and sagging; temperature 102° Fahr. Hospital care was advised, with probable operation.

The patient was admitted to the house where she was soon examined by Dr. Randall, who arranged to operate at the earliest convenient hour. The eye-grounds and ocular movements were normal. A few minutes later the patient went into a general and quite violent convulsion, more marked on the right side, the muscles of the right side of the face and right eye being involved. At this time and on the return of the convulsions later, chloroform was administered, which quieted the movements except those of the right arm and leg, but upon the withdrawal of the anæsthetic the convulsion returned. The temperature rose to 106.2° Fahr. with pulse 180 and very thready. A lumbar puncture was done finding high pressure and drawing off between three and four ounces of clear fluid, which gave temporary relief.

Under ether, the usual incision for a mastoid operation was made by Dr. Potts, letting out a little pus from the sagging canaltissues, and the intact mastoid was opened with a spoon. Some pus and granulations were found in and near the antrum and pus was seen flowing from up and back. With spoon and rongeur the course of the pus was followed until the middle cerebral fossa was freely opened and a perforation of the dura, 2 mm in width, was discovered, out of which the pus was pulsing. An incision 3.5 cm in length through the dura exposed the brain surface, which was carefully examined, but showed no sign of deeper trouble; so, after irrigation, the dural wound was sutured. A tympanomastoid exenteration was then completed on account of the history of chronic suppurative otitis media.

The convulsive movements ceased during the operation and the patient's condition improved; the pulse being of fair quality, rate 160. A restless night was followed by paralysis of the right arm and leg. When dressed on the fifth day there was some protrusion of the cerebral substance, which showed pulsation. Temperature was normal and motion was returning to the right arm.

On the tenth day the temperature began to show some febrile reaction, and a study of the accompanying chart will show the interesting and significant discrepancy between the temperature and pulse-rate, the latter becoming more and more slow and out of proportion to the former. Its hourly noting was ordered. On the fifteenth day it fell to 64; but this through an error was not recorded on the bed-chart. The child seemed comfortable, took milk well, but vomited several times on the fourteenth day. On the sixteenth day vomiting began again and the urine was voided involuntarily; the child sank into a condition of semi-stupor; pupils equal and possibly slightly sluggish. No doubt could be entertained that brain-abscess demanded intervention.

As the cerebral surface was bare for a sufficient area it was deemed best to explore for brain-abscess without an anesthetic. An Allis dry dissector was passed by Dr. Potts through the protruding and pulsating cerebral substance in a forward, inward, and slightly downward direction to the region of the tegmen. The blade was too quickly withdrawn after a little less than the full permissible penetration. It was then re-entered, passed a half inch farther, rotated partly in its track, and very slowly withdrawn. A trace of pus followed it. Forceps were then introduced and expanded and an abscess-cavity containing four or five ounces of