722 THE MECHANISM OF THE COCHLEA.

have led to important results which should soon beavailable for publication. The need of the medicalservice at the present moment is for young doctorscapable of carrying out all this special work; thecharacter and interest of the work should ensure their

being forthcoming.

The Mechanism of the Cochlea.HITHERTO current physiological teaching has pro.

vided only a hazy conception of the mechanismfor hearing in the cochlea. HELMTIOLTZ put forwardthe view that this organ contained a series of resona-tors, which were differentiated like a set of piancstrings, so that each string vibrated only in responseto one particular note. It will be remembered thatthe cochlea forms a spiral, which when unwoundconsists of two chambers placed one above the otherand separated by the basilar membrane. At oneend (the base) of the cochlea, in the wall of the upperchamber, is the window which is set in vibration bythe middle ear, while in the wall of the lower chamberis a similar window whose function is to prevent thepressure from changing inside the cochlea when theupper window moves. Both chambers contain fluid,and at the other end (the apex) of the cochlea thechambers unite, for the basilar membrane ceases justshort of the apex. The suggestion that the fibres ofthe basilar membrane can act as a resonating systemhas been current since it was pointed out that theirlength (measured across the canal) varied continu-ously from the base to the apex. Now the fibres ofa resonating system must obey the laws which governvibrating strings, so that " n," the number of vibra-tions per sec. = 1/21 t/m where " 1 " is the length ofthe fibre, " t " is the tension of the fibre, and m "

is the mass per unit length. Dr. ALBERT GRAYshowed, in 1900, that the tension of the fibres of thebasilar membrane also varied from the base to the

apex, for while the spiral ligament which attachedthe membrane to the outer wall of the cochlea was

very dense near the base, it was on the contrary veryslender near the apex. We therefore know that thefibres of the basilar membrane are differentiated fortension and length, so that the short fibres near thebase are under high tension and the long ones nearthe apex are under low tension. To complete therequirements of the formula for vibrating strings itis only necessary to discover a system by which thefibres are differentiated for mass, which differentia-tion must, as the formula demands, be applied so thatthe loading on the fibres is small near the base, butlarge near the apex. A great difficulty in supposing thatthe basilar membrane represents a system of resonat-ing strings is the fact that it is immersed in fluid Itis precisely this point which Mr. GEORGE WILKINSONconceives to be, not a difficulty, but the key of thewhole problem. At a meeting of the Section of Otologyof the Royal Society of Medicine, reported in THELANCET of June lOth last, Mr. WILKINSON outlineda, new theory of the mechanism of the cochlea whichwas well received by his professional colleagues.Recently he has developed his theme before thelarger audience afforded by the annual gathering ofthe British Association for the Advancement ofScience, and the importance of his work has been

widely appreciated. He suggests that the differentia-tion of the fibres as to mass, or the " loading " of thefibres, is brought about by the fluid in the canals.When the fibres at any point of the membranevibrate in response to an impulse from the middle ear,they will be loaded by the weight of a column of fluid

proportional to the distance of the vibrating -pointfrom the fenestra rotunda, which is the window in thebase of the cochlea. The column of fluid between thewindow and the vibrating point will be least in the case

, of a point on the membrane near the base of the cochlea,and greatest in the case of a point near the apex.

So much for Mr. WILKINSON’S theoretical concep-tion. He has provided a convincing proof of hisviews in the shape of two very ingenious models.The first is a brass box divided horizontally into twolike the cochlea unwound from its spiral. The parti-tion which represents the basilar membrane consistsof a series of parallel wires of phosphor-bronzesoldered firmly in position and covered with forma-lised gelatin. On the basilar membrane is scatteredblue enamel powder. There is a fenestra rotunda andovalis at one end of the box, respectively above andbelow the basilar membrane, the windows beingformed in each case by a rubber disc. The box isfilled with water and is completely closed. In hisfirst model Mr. WILKINSON has kept all his phosphor-bronze wires at the same tension and of the same length.Yet he finds, when he applies a vibrating tuning-fork to the rubber membrane, or fenestra rotunda,that the powder on the basilar membrane takes up adefinite position which varies with tuning-forks ofdifferent rates of vibration. Thus a 200 D.V. forkproduces a localised resonant response at a distanceof 3-3 cm. from the proximal end of the scale, whilea 400 D.V. fork produces such a response at a distanceof 0-9 cm. If one makes use of the formula forvibrating strings and supposes that the differentia-tion in resonance is due to the different loading of thewires by the fluid according to the above hypothesis,then the point of resonance to the lower tone shouldbe 4 times the distance from the windows comparedwith that for the upper note. Actually we see thatit is not 4 times, but is o;9=36 times-a very strikingagreement. Here, then, is ocular demonstrationof Mr. WIILKINSON’S contention that a svstemof transverse fibres immersed in a fluid, as itis in the cochlea, is already. by reason of theposition of the fenestrse, differentiated for resonancein regard to the effective mass of the fibres. Inhis second model, which is larger, he has carriedout a differentiation of his phosphor-bronze wires inrespect of tension and length. The differentiation oftension is effected by attaching weights of differentsizes to the ends of the individual fibres; whilelighter weights are attached to the longer fibres nearthe " apex," the heavier weights are attached to theshorter fibres near the base. In this way he hasattained a model which gives a localised resonant

response over a range exceeding four octaves.There is no doubt that Mr. WiLKiNSON has made

a considerable contribution to our knowledge of themechanism of hearing; he has presented the firstclear conception of the details of that mechanism.

Interpretation of Figures.IN the May Bulletin of the New York Department of

Health, the veteran surgeon, Prof. W. W. KEEN, ofPhiladelphia, calls attention to some of the curiousfeatures of anti-vivisection literature. Statements,repudiated and shown to be false, tend to recur fromyear to year, so that even the long-suffering Dr.WILLIAM J. MAYO once cried out in his wrath, "Thetruth is not in these people." It seems, Prof. KEENfinds, impossible for them to quote correctly, and theirprinted statements are apt to lack references other thanthe year of publication, and to be undated or even