ELIMINATION OR REDUCTION OF MOTION SICKNESS 



387 



ented" groups there was an average sickness 

 rate of 11.7 percent and a range of rates of 

 5-19 percent with 2.2 percent severely sick. 

 The "non-oriented" group had an average 

 rate of 30 percent motion sickness, and a 

 range of 25-42 percent with 10.1 percent 

 severely sick. Under the conditions of the 

 experiments, the effectiveness of visual ori- 

 entation was as great as that afforded by 

 drug medication. This finding may be 

 regarded as reliable, since it was derhon- 

 strated on observations of over 2,100 men 

 in 24 experiments. 



From these results it might be concluded 

 that the use of a visual artificial horizon 

 below deck might reduce the incidence of 

 motion sickness. This approach was actu- 

 ally adopted by Tyler in an unpublished 

 study in which he mounted an artificial 

 horizon near the operating stations of below 

 deck personnel (113). The results of the 

 study suggested that the artificial horizon 

 did have the predicted effect of reducing 

 motion sickness; but the investigator re- 

 garded the findings as tentative. This type 

 of experiment definitely needs further devel- 

 opment because of its possible practical value 

 as well as its theoretical importance. 



Magladery (68) has indicated that the 

 early British gliders had small port-hole-type 

 windows that markedly restricted the vision 

 of the horizon by glider personnel. It was 

 thought that this restriction of vision po- 

 tentiated the appearance of motion sickness 

 and it was recommended that subsequent 

 glider models be provided with larger win- 

 dows; this change was believed to have ap- 

 preciably reduced the incidence of motion 

 sickness. 



Although studies show an effect of vision 

 on motion sickness, it is yet not clearly 

 settled whether vision can exercise both a 

 facilitating and an inhibiting effect under 

 different conditions. It is worthy to note 

 that there have been no successful attempts 

 to produce symptoms of motion sickness by 

 vision alone (62), A moving picture taken 

 from the subjects' position on a swing failed 



to produce any symptoms of motion sickness 

 in subjects shown the film for over 30 min- 

 utes (85). 



Redaction in motion sickness achieved by 

 lying down is primarily the result of changing 

 the position of the head, i.e., the vestibular 

 apparatus, with respect to the applied ac- 

 celeration. In a series of experiments on 

 head and body position, it was found that 

 regardless of body position, a relation existed 

 between head position and the direction of 

 the changes in acceleration (55, 56, 78, 107). 

 The incidence of motion sickness in these 

 studies was greatest if the changes in accel- 

 eration were perpendicular to the plane 

 through the external auditory meatus and 

 the lateral canthus of the eye; lower rates 

 of motion sicloiess were noted when the 

 changes in acceleration were parallel to this 

 plane. Such findings give objective support 

 to confirm the impression that sufferers from 

 motion sickness secure relief from lying in 

 bed, beyond the mere effect of resting alone. 



These results also afford evidence that the 

 effect of acceleration upon the viscera and 

 blood column is not an important factor, 

 if present at all, in the production of motion 

 sickness. Indirect confirmation is also con- 

 tained in the observation that no relation 

 existed between the amount of visceral 

 movement in individuals and susceptibility 

 to motion sickness (69). 



Numerous factors have been mentioned in 

 the folklore of motion sickness that are now 

 known to be largely irrelevant. The use of 

 special diets, conditioning exercises, pre-em- 

 barkation cathartics, and other clinical de- 

 vices have been minimized in the face of 

 experimental evidence (114). Fatigue, 

 odors, illness, and other factors have also 

 been mentioned in connection with motion 

 sickness. Without specific information 

 available, it is difficult to estimate their 

 importance, although in view of the trend 

 toward defining motion sicloiess with greater 

 specificity, it is reasonable to view the im- 

 portance of such possible determinants with 

 suspicion. It is worth noting here that any 



