l82 



NATURE 



[May 8, 1919 



THE FUNCTIONS OF THE INTERNAL 

 EAR. 

 Equilibrium and Vertigo. By Dr. Isaac H. Jones. 

 . With an analysis of pathologic cases by Dr. 

 Lewis P^isher. Pp. xv + 444. (Philadelphia and 

 London: J. B. Lippincott Co., 1918.) Price 

 21S, net. 



ALTHOUGH the internal ear or labyrinth of 

 man's body is so small that it may be placed 

 within a hazel-nut of moderate size, it contains 

 two organs of the first importance — one for the 

 recognition of sound, the other for the recogni- 

 tion of movement. A hundred years ago anato- 

 mists and physiologists had no suspicion that the 

 internal ear was a double organ. When John 

 Hunter discovered that fishes had an elaborate 

 internal ear or labyrinth, with three well-developed 

 semicircular canals, he believed he had established 

 as a fact that fishes are furnished with the power 

 of hearing. The discovery made by Flourens in 

 1825 that a partial or total destruction of the 

 semicircular canals of a pigeon deprived the bird 

 of all power of controlling its movements was 

 altogether unexpected and puzzling. No one had 

 suspected that the vertebrate animal was fur- 

 nished with an organ which silently answered the 

 purposes of a mariner's compass, nor could it have 

 been anticipated that such an instrument should 

 form part of the apparatus known as the internal 

 ear or labyrinth. 



After the initial discovery by Flourens our 

 knowledge of the equilibrating function of the 

 labyrinth developed slowly and intermittently, 

 being regarded as a matter of mere academical 

 interest until 1905. In that year Robert Bardny, 

 lecturer on aural surgery in the University of 

 Vienna, made a chance observation which led to 

 a knowledge of this obscure and silent function 

 of the ear becoming a matter of immediate prac- 

 tical importance to every medical man. Barany 

 noted that when he douched the ear-passage of a 

 patient with cold water, the eyes immediately 

 swung in one direction ; when he employed hot 

 water in place of cold, the eyes moved in a 

 reverse direction. He immediately suspected, and 

 proceeded to prove, that the douches set up con- 

 vection currents of opposite directions in the ad- 

 joining semicircular canals, the cold douche giving 

 a downward flow, the hot one in a reverse direc- 

 tion. If there was a diseased or disordered con- 

 dition of the canals, then no response was given 

 by the eyes, because the automatic mechanism 

 which fixes the gaze on an object when one's head 

 is turned no longer acts. 



In 1909 Bcirany made the further and even more 

 important observation that the action of every 

 muscle of the body was influenced by messages 

 or stimuli which arise in the semicircular canals 

 and ^adjoining parts. When he set up currents 

 within the canals either by douching or by seating 

 the patient on a rotating chair, he found that the 

 power of carrying out precise movements was 

 lost in every part of the body. Thus the canali- 

 cular mechanism of the ear establishes a con- 

 NO. 2584, VOL. 103] 



nection with every part of the executive elements 

 of the central nervous system. By testing the 

 reactions yielded by the semicircular canals, the 

 physician can explore the central nervous system 

 and ascertain whether or not a multitude of its 

 connections are in a normal condition of health. 



In no country has the practical application of 

 Bdrany's discoveries been more vigorously fol- 

 lowed up than in the medical schools of the 

 United States. That has been particularly the 

 case in the University of Pennsylvania, where 

 Dr. Isaac H. Jones holds the post of instructor 

 in "neuro-otology," and at the same time acts 

 as laryngologist to the Philadelphia General Hos- 

 pital. In the work under notice Dr. Jones not 

 only introduces his readers to the latest teaching 

 regarding the functions and connections of the 

 labyrinth, but also adds certain discoveries 

 of his own. He claims that the nerve- 

 fibres from the external or horizontal canals 

 pursue a separate course and form different con- 

 nections in the central nervous system from the 

 fibres which issue from the vertical canals — the 

 superior and posterior. The section of this book 

 in which Dr. Lewis Fisher gives an analysis of 

 a great number of cases where a defect had 

 occurred in the balancing mechanism of the body 

 will prove of particular interest to clinicians. Of 

 more immediate importance are the chapters 

 devoted to a description of the tests applied to 

 candidates for the aviation corps, for it is mani- 

 fest that a sound and sensitive equilibrating 

 mechanism is as necessary for a flying man as 

 for a bird. The essential tests are based on 

 Bdrany's discoveries. 



Dr. Jones does not touch on the very interesting 

 problem of how two functions so different in 

 nature as are those of balancing and of hearing 

 became associated in the same organ, nor is our 

 knowledge sufficiently complete to permit us to 

 tell the story in full. Yet from a double source — 

 from the evidence of embryology and of compara- 

 tive anatomy- — we know for certain that the in- 

 ternal ear was evolved as a balancing mechanism 

 — as a sense-organ to provide the body with a 

 knowledge of its position and of its movements 

 —and that the part which serves the function 

 of hearing is a comparatively late addition or 

 extension. In making that addition Nature intro- 

 duced no new principle, but by a slight modifica- 

 tion of the apparatus used for registering changes 

 in the position of the body she evolved an instru- 

 ment for the registering of sound-waves and for 

 their conversion into nerve stimuli. The basal 

 design of the labyrinth is a minute closed sac 

 filled with fluid. On its floor is a carpet of cells 

 bearing cilia; on the cilia is poised a load. The 

 slightest change in the position of the body of the 

 animal is accompanied by a change in the position 

 of the load and a bending of the cilia. In a 

 manner which we can only guess, the mechanical 

 bending of the cilia is converted by their basal 

 cells into nerve stimuli. For the detection of 

 bodily movements, part of the closed sac became 

 converted into semicircular canals, and across each 



