In previous papers on this subject ' the attempt was made to present, from observed cases, an inference as to the influence of combinations of pressure, extrinsic and intrinsic, in the production of vertiginous symptoms, with especial reference to the study of those cases in which the extrinsic cause might be regarded as predominant. The hypothetic basis for these observations was that, while moderate degrees of variation, from the constant of the ampullary end apparatus, could be compensated

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... r by the provisions for movement in the normal sound transmitting apparatus, and in the aqueducts, greater degrees of variation, either beyond the possibility of normal compensation, or inhibition of the normal compensation itself, would be productive of symptomatic results unless the inhibition had been one of such slow increase as to permit of gradual accommodation to the" abnormal condition, evidenced, for instance, in cases of progressive stapes fixation, or of progressive contraction of the tensor tympani muscle. In the study of a symptom of such varied causation, it is only by compilation of observations from different sources that reliable differentiative data can be obtained, and this is especially true of the more vague, the less acutely pronounced manifestations, those in which the prime causative factor is determinable only by an elaborate process of successive eliminations. With a well-marked intralabyrinthine hemorrhage, or effusion, the diagnosis, both as to the character and the location of the lesion, is usually easily determinable, and this is equally true in cases with pronounced evidence of intralabyrinthine pressure of extrinsic origin. In the former instances, when once the acute stage has passed, and the effect of the localized intralabyrinthine pressure has been compensated for by natural processes of repair, the vertiginous symptoms recur only under conditions of like causation, a repetition of the hemorrhage or effusion, for instance; or, more frequently, recurrently, under the temporarily increased intralabyrinthine pressure incident to such a cause as a localized suspense of vasomotor inhibition. In the latter instances the symptoms of ampullary disturbance may persist with only such variations as are incident to intralabyrinthine circulatory changes, until the major, accessible, extrinsic, pressure cause is removed, be it a new growth or an epidermal accumulation in a suppurative middle ear, an extensible cicatrix of the drumhead transmitting preponderating atmospheric pressure to the stapes or a muscular retraction to be overcome by the creation and protracted main-1 Middle Ear Tension, or Pressure Abnormality as a Factor in the Causation of Auditory Vertigo, Trans. Am. Otol. Soc. Vertigo of Aural Causation, Boston Med. and Surg. Joue., 1905. tenance of a partial vacuum in the external auditory canal. In cases of recurrent vertiginous attack with inadequate evidence of an intralabyrinthine or of an accessible extrinsic pressure factor, it seemed desirable to test the effect, upon the line instituted by Babinski, of decrease of intracranial and, correspondingly, of intralabyrinthine pressure by some means which would leave the auditory apparatus intact, an additional incentive to such a series, of investigations being previous experiences in disturbances of intralabyrinthine pressure, incident to investigations in regard to the removal of the stapes.2 Under these considerations, in conjunction with Dr. J. J. Putnam, in a series of adult cases in which the extrinsic pressure factor was at a minimum, or absent, lumbar puncture was practiced with results thus far sufficiently favorable to warrant a continuation of the investigation. In no instance were there more unfavorable consequences than severe headache of several days' duration in three instances; in all of the cases treated there has been a temporary amelioration of the condition, and, in the majority, entire relief from the vertiginous attacks during a period of from a few months to three years, the latter being the major limit of observation. In two cases in which the attacks recurred within a year the onsets were less severe and the complex incomplete, and a repetition of the lumbar puncture was followed by entire relief up to the date of the last observation. In all instances the withdrawal of fluid ranged from 10 to 15 ccm., and the cases were kept under immediate observation for several days. A typical case is that of a student, a young man twenty-four years of age, who had, during one and one-half years previous to his coming under observation, attacks of vertigo, preceded by intense circulatory tinnitus and followed by nausea. These attacks occurred at irregular intervals, varied in degree of severity and seriously interfered with the prosecution of his law studies. Aural examination showed both middle ears to be normal in appearance, the hearing in the left ear normal and in the right ear much impaired for tones of medium high pitch and wanting, both aerially and by bone conduction, for tones of medium low pitch. Careful examination revealed no central cause or disturbance, and lumbar puncture was practiced with withdrawal of 15 ccm., since which time, three years ago, there has been no repetition of the vertiginous symptoms and only such occasional slight dizziness as could be accounted for by increased cerebral circulation incident to protracted study and fatigue. Immediately after the lumbar puncture the hearing in the right ear was found to have improved for tones of medium high pitch, having doubled for the Pollitzer acoumeter, for instance. This improvement in hearing increased up to one year after the date of the lumbar puncture and has since then slowly decreased, without, however, reaching its first level; the hearing for tones of medium low pitch remaining unchanged. Another case is that of a man fifty-four years of age, with a history of a first occurrence of Ménière's complex of symptoms in the right ear two years previously, '