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A hundred years ago: Fons et origo mali maris: or, the cause of sea sickness

By Kenneth F. Lund, M.B. (Lond.), B.A. (Cantab.).

Late Master, Coombe Hospital, Dublin.

By Kenneth F. Lund, M.B. (Lond.), B.A. (Cantab.).

Late Master, Coombe Hospital, Dublin.

Extracted from the August 1907 issue of The Practitioner

Vomiting is produced by direct stimulation of the medulla, or by reflex irritation through one or more sensory nerves. Sea sickness is essentially a condition brought about by the motion of a ship, and, as the reflex causes of vomiting are so numerous, one must eliminate from the consideration of the cause of sea sickness all those which have no reference to motion.

It is a curious, perhaps analogous fact, that there is one class of sorely afflicted people who are never sea sick. I refer to deaf mutes. By deaf mutes I mean those who have been born deaf, or who have lost their hearing at a very early age. I have not been able to discover at what age the onset of deafness fails to bring with it immunity from sea sickness, but those who become deaf late in life still suffer from the complaint. I do know of one gentleman who lost his hearing at the age of twenty, and was never sea sick after.

A party of twenty-five deaf American gentlemen crossed the Atlantic, in 1889, to attend the Paris Congress of Deaf Mutes. It was a very rough voyage, and every passenger was ill except the deaf mutes, who had all the tables in the dining saloon to themselves. A deaf lady was a passenger by the same boat, and she and the captain had one table to themselves throughout the voyage.

Another idiosyncrasy, peculiar to deaf mutes, is that they do not experience that sensation in the stomach once described as "a momentary displacement of the viscera" to which most of us are liable on descending in a lift, or in swinging. Nor have the deaf mutes, to whom I have spoken, experienced nausea, or sickness when climbing, or looking down precipices.

The connection between sea-sickness and the organ of hearing does not at first sight seem obvious, but the simple act of syringing the ear produces, in some people, all the symptoms of mal de mer. A relative of mine says that he can produce the sensations of being at sea by the mere act of syringing his own ear. He turns faint and giddy, vomits, and is obliged to lie down for several hours to prevent the recurrence of the vomiting.

The following case is also of interest with reference to the connection between the auditory organ and motion:-
A young lady, when 17 years old, had a severe attack of scarlet fever and diphtheria. The glands in her neck suppurated, and she entirely lost the hearing of one ear. She is now married and has one child. She is unable to ride a bicycle, or to walk in the dark; indeed, she is very uncertain of her walking even in daylight. But her eyesight is normal, reacting to light and accommodation, and there is no astigmatism. From being a very bad sailor, she is now quite happy at sea, and never suffers from sea sickness, although her hearing is not entirely destroyed. In reviewing the various causes of sea sickness put forward by different authorities, I come to the conclusion that:-
(a) Strictly speaking, the vomiting is not due to the unusual impression of vision, as it occurs in some people on land; it occurs even when the eyes are closed, and the blind suffer as much as, if not more than, sighted people.
(b) It is not due to smell. Any bad or unpleasant odour may cause vomiting. This cause is common to people on land or sea, in fact, to any or all, including deaf mutes, who have sensitive nasal organs.
(c) It is not due to momentary displacement of viscera which seems to occur in swinging, or in descending in a lift. The sensation is present whether the eyes are open or closed, but it does not occur in deaf mutes.
(d) There is some mechanism in the auditory organ, possibly in the system of semicircular canals, which is directly affected by the oscillations of a vessel at sea, and which acts as a stimulus to the vomiting centre.

With regard to the nature of the movement, it may be pointed out that it is one of sudden descent, as any one may prove for himself by trying a few experiments in a lift. I have certainly noticed a peculiar sensation in my ears, synchronous with the sensation in the epigastrium, on the sudden downward movement of a lift, and experienced no sensation on the upward movement. It is conceivable that these sudden and unexpected movements may take the endolymph in the semicircular canals, so to speak, unawares, and create a condensation or rarefaction, or both alternately, in one part or another of the labyrinth, thereby altering the pressure in the nerve ending and thus causing a direct stimulus to vomit.

The routine treatment adopted for combating sea sickness is compatible with this theory, as it mainly consists in lowering the sensibility, or conductivity of the afferent nerves, or in numbing the vomiting centre by the action of such drugs as potassium bromide, chloral, or morphine.

If this theory is not altogether convincing with regard to the origin of sea sickness, it may possibly induce anatomists and pathologists to enquire more closely into the exact nature of the lesion that occurs in the auditory organs of deaf mutes; although there are obvious difficulties in the way of procuring subjects for examination and dissection.

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