4'H On Sea-Sicbiess, 



the sam:* manner, and for the same reason, the blood no 

 longer presses downwards with its whole weight, and will he 

 driven, upward.^, by the ela^^ticity which before was iDerely 

 sufficient to support it. | 



'I'he sickness occasioned by swinging is evidently from 

 the same causes as sea-sickuess, aiid that direction oF ihc 

 motion which occasions the most piercing sensation ot un- 

 easiness, is contormable to the explanation above given. 



It is in desjcending torvvards that this sensation is per- 

 ceived ; tor, then the blood has the greatest tendency to 

 move from tlie teet towards the head, since the line joining 

 them is in the direction of the motion. But when, in the 

 descent backwards, the motion is transverse to the line of 

 the boiiv, it occasions little comparative inconvenience, 

 because ttte tendency to propel the blood towards the heaJ 

 is then inconsiderable. 



The regularity of" the motion in swinging, aflTorded me 

 an apparently favourable opportunity for trying the effect 

 of inspiraticm; but althougiwhe advantage was manifest, 

 I must confess, it did net fully equal the expectations I had 

 formed from my experience at sea. It is possible that the 

 suddenness of the descent may in this case be too great 

 to be fully counteracted by such means ; but I am inclined 

 to think that the contents of the intestines are also af- 

 fected by the sanie cause as the blood ; and it these have 

 any direct disposition to regurgitate, this consequence will 

 be in no degree counteracted by the process of respira- 

 tion. 



A friend of mine informed me that he had endeavoured 

 to counteract this mechanical efiect upon the stomach, and 

 had experienced immediate relief from a slight degree of 

 sea- sickness, by l)in'g down upon the deck with his head 

 towarfls the stem of the vessel ; by means of which, upon 

 pitching, he was in the attitude of a person descending 

 backwards in a swing. 



Whether the stomach be or be not thus primarily af- 

 fected, or only by svnipattiv with the brain, the sensation 

 of sinkinsi; is in all cases referred directly to the stomach, 

 which is seized with such instantaneous retching, that no 

 person who has not been so situated can form a just con- 

 ception of it*. 



In 



* There is one occasion upon wliirh a slighter f.ens'.'tion of this kind h 

 perceived, and it appears to indicate th'.' direction of the m';tion from 

 which it arises, to be downwards. " In a country subject to frequent re- 

 turns of earthquakes," it is §aixif tliat " a few minutes before any ihuck came, 



niJLny 

 ^ Phil. Trans, vol. jlii. p. 41. 



