/790 THE SENSE OF EQUILIBRIUM 



unusual rotation, say, around the longitudinal axis of the body, gives 

 rise to a horizontal nystagmus of the eyes. This phenomenon con- 

 sists in a slow lateral movement of the eyes in the plane of the rotation 

 which, however, is soon stopped and superseded by an abrupt return 

 of the eyes into the midline. This rotation-nystagmus is to be sharply 

 differentiated from that form of nystagmus which is frequently 

 exhibited by persons looking out of the window of a railway car. The 

 former occurs even in the dark and in blind persons, while the latter 

 does not, and may be suppressed by fixedly gazing into space. A 

 nystagmus of the entire head is often observed in birds when made to 

 stand upon a rotating surface. The head is at first turned against the 

 direction of the rotation and is then made to execute jerky move- 

 ments around the long axis of the body. 



Compensatory movements of the entire body are frequently 

 noticed after rather excessive rotation. Thus, if we turn around the 

 longitudinal axis of our body a number of times and then suddenly 

 stop, it will be found that the objects in space continue to move against 

 the direction of the rotation, while we ourselves leave our previous 

 position and sway toward the rotation. It is to be noted, how- 

 ever, that this compensation is forced upon us reflexly and should not 

 be mistaken for the ordinary effects of the momentum of the rotation. 

 In addition, it is easily observed that these compensatory movements 

 are confined chiefly to the head and trunk and would, in the absence 

 of corresponding movements of the legs and arms, give rise to a com- 

 plete loss of equilibrium. 



These rotation experiments should be executed with some caution, 

 because in hypersensitive persons they are prone to produce nausea, 

 vomiting, muscular weakness, disturbances in vision and slight 

 cardio-inhibitory effects. For this reason, it is commonly held that 

 seasickness is caused by an unusual and excessive stimulation of the 

 static and dynamic sense-organs. A similar complex of symptoms, 

 aggravated, however, by vertigo, forced movements and a constant 

 ringing in the ears, is presented by Meniere's disease.^ The latter 

 seems to have its origin in an inflammatory and hemorrhagic affec- 

 tion of the semicircular canals and neighboring nerve fibers. It is 

 also well recognized that the injection of solutions into the tympanic 

 cavity as a curative means in affections of the middle ear may give 

 rise to vertigo and nystagmus; in fact, in some persons, loud noises 

 suffice to induce these symptoms. 



The character of the results obtained with deaf persons, differs with 

 the extent of the lesion. Inasmuch as only about 65 per cent, of these 

 persons show a lesion of the canals in addition to that of the cochlea, 

 it cannot surprise us to find that many of them present absolutely 

 no disorders of their senses of position and movement. The others 

 have learned in the course of time to compensate for the disturbances 



1 Gaz. m^d. de Paris, 1861; also: Frankl-Hochwart, Das Menier^sche Sympto- 

 men-complex, Wien, 1906. 



