Mat 6, 1921] 



SCIENCE 



425 



nerve. Leo (1893) reported that when the 

 otoliths were removed from both ears com- 

 pensatory movements were perhaps weakened 

 but were not completely done away with; but 

 that on the other hand the compensatory posi- 

 tion was not retained after the movement 

 ceased. Parker (1909) and I (1910) botli 

 found that the removal of the large otolith of 

 the sacculus had no effect whatever on the 

 equilibrium reactions, static or dynamic. 

 Moreover I found that after removal of tlie 

 otoliths from the sacculus and in addition all 

 the six ampullse good comi>ensatory motions 

 occurred to rotations in all planes except the 

 horizontal if only the little otolith of the 

 recessus uti-iculi remained uninjured. If now 

 I removed the otolith of the recessus also 

 every trace of labyrinthine reaction perman- 

 ently disappeared. It made no difference in 

 the result, however, if I omitted the removal 

 of the saccular otolith. 



The removal of the otolith from the recessus 

 of the utricle without too great damage to the 

 connection of the utriculus with the mouths 

 of the anterior vertical and horizontal canals, 

 especially the latter, was so great that at first 

 it seemed impossible. In my earlier experi- 

 ments I was puzzled by the fact after com- 

 plete removal of the otolith the ampulla of 

 the horizontal canal always ceased to func- 

 tion. When at last I was able to make a 

 small incision through the delicate wall of 

 the utriculus and wash out the otolith with a 

 fine pipette I found not only that compensa- 

 tory movements occurred in response to rota- 

 tions in all planes, but that the compensatory 

 positions were retained. Thus it becomes ap- 

 parent that not only the otolith-organs with- 

 out the ampullse but also the ampullse without 

 the otolith-organs possess both dynamic and 

 static functions. I may say here that in 

 either case, after loss of the ampullse or after 

 loss of the otoliths, the reactions are notice- 

 ably slower and weaker than in the normal 

 animal; evidently the two sets of structures 

 reinforce each other. 



(6) Stimulation Experiments 

 Stimulation experiments on the otolith- 

 organs have been attempted by many ob- 



servers but usually with inconstant, contra- 

 dictory or negative results. Kubo (1906), 

 however, reported very definite responses to 

 stimulation by the application of pressure to 

 the otolith. According to his statements the 

 otoliths have definitely localized functions 

 corresponding to those of the semicircular 

 canals. These localizations corresponded to 

 the statement of Breuer that the otoliths like 

 the semicircular canals are arranged in three 

 planes in space, each responding to motion in 

 its own plane. Kubo states that the otolith 

 of the utriculus when pushed anteriorly 

 causes the eyes to roll backward, tliat is, to 

 rotate on their axis, nasal pole up, which is 

 the compensatory movement occurring when 

 the head is tilted downward. Moving this 

 otolith backward had no effect. In an 

 analogous manner moving the large otolith of 

 the sacculus backward gave the same move- 

 ment as tilting the head up, and pushing the 

 same otolith outwards from the median line 

 gave the same reaction as that which comes 

 from rotating the body to the same side 

 around the longitudinal axis. In the light of 

 our present knowledge Kubo's results are 

 perfectly easy to understand, but are of 

 absolutely no scientific value. His experi- 

 ments were made without removing the 

 ampulke and he specifically states that they 

 succeeded best when performed without re- 

 moving " the membranous capsule of the 

 gelatinous mass." In each case the result 

 was just what would occur when he acciden- 

 tally produced a change of tension on the 

 nearest ampulla. 



In order to study the effect of stimulation 

 of any of the labyrinthine structures it is, of 

 course, necessary to make sure that the struc- 

 ture in question is really the one in which 

 the excitation takes place, since, as we have 

 seen, all the compensatory movements which 

 can be excited through the otolith organs in 

 the absence of the semicircular canals can 

 also be excited through the semicircular 

 canals in the absence of the otolith organs. 

 It is then evidently useless to attempt to 

 determine the action of the otolith by stimu- 

 lation experiments so long as the ampullse of 

 the canals are in place. The only completely 



