Sea-sickness is a variety of vomiting deserving of special notice. It is often preceded by premonitory symptoms, which appear almost immediately after a susceptible person is exposed to the motion of rolling water in a vessel or boat, and are as distressing as the vomiting itself. Amongst these symptoms may be mentioned vertigo and headache, with a peculiar feeling of sinking and distress about the pit of the stomach. Vomiting, however, in general, soon comes on, accompanied with convulsive heaving of the stomach, and such an indescribable feeling of prostration as to render the patient utterly regardless of what is going on around him, and almost indifferent to life. Moreover, pallor and cold sweat are commonly present, with disturbance of the action of the bowels, usually constipation, but occasionally diarrhoea. The susceptibility to this troublesome affection varies extremely in different persons. Some never suffer from it, others only on their first voyage, and others, again, like Nelson, in every fresh voyage they take; with some it continues but a few hours, while others suffer almost continuously throughout a long voyage. In the great majority of cases the sickness disappears in a few days, unless the weather be very boisterous. It almost always ceases on landing, although more or less giddiness may prevail for some hours. Though a very distressing malady it is rarely serious, but sometimes is so severe and prolonged as to prove fatal. Infants and aged persons are supposed to possess a comparative immunity from sea-sickness, while as a general rule women suffer more than men. According to Dr Althaus, persons with a strong heart and a slow pulse generally suffer little from sea-sickness, while irritable people, with a quick pulse and a tendency to palpitation, are more liable to be affected; and he thus accounts for different liability of different nations to this affection; 'for, as a rule, the French and Italians being of a more irritable temper suffer most from the disorder, the Germans less, and the English least.'
The primary cause (or rather condition) of sea-sickness is the motion of the ship; and the pitching of a vessel, or alternate rising and falling of the bow and stern, is especially apt to produce it. It is less felt in large and heavily ballasted vessels, because the movements referred to are least perceptible in them. Other more or less regularly repeated oscillatory movements produce a precisely similar condition in some people; the motion of a swing or a toboggan in particular. Some suffer in a railway journey, especially when sitting with their backs to the engine; while a few individuals are so intensely susceptible that even a short drive in a carriage or omnibus is enough to induce nausea and vomiting.
The mode in which such causes produce sea-sickness has been much discussed; but it is now generally believed to be by a reflex disturbance of the nervous system, induced by the unusual and violent stimulation of the sensory organs concerned in the maintenance of the equilibrium of the body, particularly the semicircular canals (see EAR) and the eyes, and also of the viscera, particularly the stomach. This is not inconsistent with the view of Dr Chapman, who gave much attention to the subject, and held that the motions of the vessel cause the accumulation of an undue amount of 'blood in the nervous centres along the back, and especially in those segments of the spinal cord related to the stomach, and the muscles concerned in vomiting.' He accordingly believed that the only scientific and really effective remedy for this disorder must be one which has the power of lessening the amount of blood in the whole of the nervous centres along the back, and this can be done by lowering the temperature of the spinal region by the local application of ice. For a description of Dr Chapman's 'spinal ice-bags' (which may be obtained from any respectable surgical instrument-maker), and for the method of applying them, we must refer to his work On Sea-sickness (1864). They have undoubtedly proved of great value in many cases. Another method of treatment, which is less difficult to employ and sometimes gives good results, is to make the sufferer breathe deeply and regularly, timing the respirations by the watch at about fifteen to the minute.
Those who are susceptible to this distressing affection and have not the opportunity of trying the ice-bags, may, at all events, diminish the sever- ity of the vomiting by assuming, and as long as possible retaining, the horizontal position as nearly as possible in the centre of the ship's movement, and keeping the eyes closed. Compression of the abdomen by means of a broad tight belt sometimes gives relief. Fresh air and light diet are undoubtedly of great importance. A little arrow-root, flavoured with brandy or sherry, is usually a kind of food that will most easily remain on the stomach, when the severity of the symptoms is abating. The maintenance of the surface temperature, by warm blankets and hot bottles if necessary, should be attended to. The application of a mustard poultice or stimulating liniment to the epigastrium is often useful. Sucking or swallowing small lumps of ice also tends to diminish the tendency to vomiting. As soon as possible the sufferer should go on deck, and try to move about; if this can be done the nervous system undoubtedly becomes more quickly accustomed to the unwonted conditions under which it is placed.
With regard to drugs, no specific has been discovered, nor is it likely that there ever will be. But something can often be done by medication both before and during a voyage. First in importance are purgatives. The bowels should be freely relieved the day before the voyage begins, and should never be allowed to become constipated. The administration of a tonic (e.g. Easton's syrup) for a few days before starting is also useful; and regular doses of the bromides, commenced just before going on board, sometimes diminish the intensity of the malady. When it has set in, chloroform (a few drops on a piece of sugar), opium, chloral may do good; and cocaine, nitrite of amyl, nitroglycerine, and antipyrin, drugs more recently introduced, have all been strongly recommended. But with all such remedies disappointment is only too common.
See Dr T. Dutton, Sea-sickness (2d ed. 1891); and a small monograph by Rosenbach (Berlin, 1891).