20 R. M. Bache on Sea-sickness. | 



to riding in a carriage, nauseated by riding with the hack to- 

 wards the direction in which he is proceeding, for the appear- 

 ance of motion "per se" does not nauseate, nor can motion 

 "perse" nauseate in that instance. The effect is derived from 

 consciousness of motion perceived by two senses at least, while 

 at the same time, the appearance of objects violates the habitual 

 impression produced by the sight of them. In the dark, the 

 effect must be derived from pure imagination. If we grant then, 

 that a particular mode of progress in a carriage can nauseate 

 one accustomed to a carriage (and it is often seen) and we 

 grant at the same time, that appearance of motion "per se" is 

 not nauseating (and this I have proved) and we know also, in 

 the case spoken of, that motion " per se " could not have pro- 

 duced the sensation of nausea (because the motion is the same 

 in any position, and the person is habituated to one) we must 

 then acknowledge that the nausea is produced neither by the 

 motion "per se," nor by the appearance of motion "per se," but 

 by a conflict of the two senses of feeling and sight. If this 

 can be inferred in the case of one accustomed to the motion of a 

 carriage, it must apply with more force to one unaccustomed to it 



So thoroughly have the senses created a conception of mo- 

 tion, that the exclusion of sight does not alter the idea of its 

 appearance, nor alter the idea of the appearance of violation 

 of preconceived effects. The mental picture is always present 

 If the exclusion of the sight did alter these ideas, the closing 

 of the eyes would in one of the cases just mentioned, save 

 from nausea a person unaccustomed to riding in a certain po- 

 sition, and in the other case, would secure immunity from nau- 

 sea to the person unaccustomed to riding at all. But it does 

 not save them, which shows that the mental picture of progress 

 and of unwonted effects, takes the place of that produced by ac- 

 tual vision. It is immaterial whether the sight is acting or not 

 acting. Whatever senses exist in an individual, have conjointly 

 created a well defined idea of the contrasted effects of motion, 

 and. this conception is always evident to the mind without the 

 continued intervention of all the authors of the conception. 



Having shown that a certain motion is nauseating, but is not 

 nauseating " per se," we may fairly infer that no motion is nau- 

 seating "per se." Perhaps in very violent motions, there may be 

 some mechanical effect produced by the movement of the stom- 

 ach — this is not a primary cause of sea-sickness, but an aggrava- 

 tion of it. Otherwise, it must be supposed that the stomach of 

 a sailor becomes entirely changed in its nature. 



The law to be deduced from what I have attempted to demon- 

 strate is this— that the violation of the habitual conception of 

 contrasted effects of motion, is the cause of the nauseation which 

 occurs during novel motions — and the cause is not motion 

 " per se," nor the appearance of motion "per se." 



