442 On Sea- Sickness, 



served the sound that occurs upon stopping the ears, but 

 ascribed it, according to the notions that prevailed in his 

 lime, to the hurried motions of the animal spirits*. 



Part IL On Sea- Sickness, 



The second remark which I have to offer to the society 

 relates to sea-sickness, the cause of which has not hitherto 

 been fully explained ; and although the explanation which 

 I am about to propose, niay not appear altogether satisfac- 

 tory to persons who, when at sea, are also rendered giddy 

 by the incessant motion of the waves, and-are consequently 

 liable to consider as cause and effect phaenomena which in 

 their minds are constantly associated ; yet the observation 

 on which it is founded may deserve to be recorded, on 

 account of the degree of relief that may be obtained in that 

 most distressing atiection. 



After I had been harassed by sea-sickness during a short 

 voyage for some days, and had in vain attempted to ac- 

 count for the difference between the inexperienced passen- 

 ger, and those around him more accustomed to the motion 

 of the sea, I imperceptibly acquired some power of resist- 

 ing its eifects, and had the good fortune to observe a pe- 

 culiarity in my mode of respiration, evidently connected 

 with the motion of the vessel, but of which, in my then 

 enfeebled state, I was unable to investigate either the cause 

 or consequence. In waking from a state of very disturbed 

 sleep, T found that my respirations were not taken with 

 the accustomed uniformity, but were interrupted by irre- 

 gular pauses,' with an appearance of watching for some 

 favourable opportunity for making the succeeding effort ; 

 and it seemed as if the act of inspiration were in some 

 manner to be guided by the tendency of the vessel to pitch 

 with an uneasy motion. 



T^he mode by which I afterwards conceived that this 

 action could priniarily affect the system, was by its in- 

 fluence on the motion of the blood ; for, at the same in- 

 stant that the chest is dilated for reception of air, its vessels 

 become also more open to the reception of the blood, so 

 that the return of blood from the head is more free than at 

 any other period of a complete respiration. On the con- 

 trary, by the act of expelling air from the lungs, the ingress 

 of blood is so far obstructed^ that, when the surface of the 



* Vera itaquc ratio expcrimenti ]irxdicti est, quia ia di^^ito et brachio 

 totoque corpore conlinuato fnint niulti molus ac tremores, ob bpirituum 

 •a^itationem hue illuc perpetuo accurrentium. Grijiialdi, Pliysicomathesis 

 tie Lumine, p. 38.3. 



brain 



