R M. Bache on Seasickness. 23 



time, to reconcile the evidence of his senses. If he possesses 

 sight, it will have been educated in conformity with unequal 

 motions, just as it was educated from childhood to comparatively 

 equal ones, or if he is blind, his conception of the appearance of 

 motion, will have been reconciled with motion experienced. In 

 either case, it is the conception of the appearance of motion, as 

 contrasted with the feeling, which conception will have reconci'led 

 itself with existing conditions. Both those who see, and the 

 blind possess this habitual conception, which is never shut out 

 from the mind as has been shown. Closing the eyes will not 

 discard it. If it did, every one subjected to unusual motion 

 could in that way, secure immunity from nausea. This has been 

 shown not to be the case. 



Let us now consider the peculiar effect of unequal motions 

 upon the human body. It is my conviction that motion is nau- 

 seating whenever the estimate of its extent does not correctly 

 precede it. The mind mechanically calculates what is to take 

 place while it is taking place. 



I shall now endeavor to show, that "motion is nauseating 

 whenever the estimate of its extent does not correctly precede 

 it.'' I have already shown that motion is not nauseating " per 

 se." I have also shown, that when it does nauseate, it is when 

 the brain is impressed. The question naturally suggests itself 

 here, as to what there is in the impression produced on the 

 brain which affects us unpleasantly and produces nausea. It is 

 the idea of undefined movement of the body of the observer. 

 Back of this I do not pretend to go. Nature has so constituted 

 us, that undefined motion is repugnant to our organizations. 

 Kauseation from motion proceeds from the idea present to the 

 imagination, that the body is the subject of undefined motion. 

 The nauseation of sea-sickness, of course, eminently proceeds 

 from undefined motion. But to the proof— an experiment which 

 any one can make. I have often lain awake at night in the 

 cabin of some great ship at sea, and guaged the motion and cal- 

 culated the capability of the passengers to resist an access of nau- 

 sea. Choose a time, when there is a regular sea and wind, when 

 the ship ploughs along pretty evenly. Now and then, seas will 

 •rise somewhat higher than the rest. Sea-sick passengers habit- 

 uated to uniform motion — at the intervals when the ship has been 

 accustomed to rise or to fall, feel that they rise still higher or 

 fall still lower. The difference in motion is not perceptible in 

 violence, and yet causes many to give involuntary evidence of 

 the occupancy of their state rooms. The strain of fancy is ever 

 exerted and solicitous to imagine and attain the turning point, 

 although after it is gained, the motion, as in a descent, may be 

 still more rapid. Let any one who has been at sea, recall hov» 



3 movement m one direction, even a long 

 rise upon a wave, when the motion is certainly not as swifl as in 



