NAIAD.—Sea-sickness cannot be considered as a disease of the stomach. It is caused by the motion acting in some way upon the brain. How it acts is not quite certain; possibly it is by interfering with the blood supply of the brain, or it might be due to a succession of slight “concussions.” An exactly similar form of sickness occurs in some persons from swinging, or who have been patronising the “giddy-go-round.” Also any injury to the head may be followed by sickness. How to prevent sea-sickness is a question which is confessedly a puzzle to all. The peculiarity of this form of vomiting is that it bears no relation to food. It is no more common after than before meals, and the vomiting produces little or no relief. We think everybody has her own little specific for sea-sickness, and it is as useless as her neighbour’s. Obviously, from what has been said above, no remedy which acts upon the stomach can prevent sickness, because it is a nervous and not a gastric symptom. We may hope one day to discover how to prevent sea-sickness; at present we cannot do so by any means. AN ANXIOUS GIRL.—Read our answer to “A Gaiety Girl.” The question of infection and epidemics is a most puzzling one for the public to understand. And yet it is of vast importance that it should understand it, for with the public, and not with the medical profession, lies the power of stamping out infectious diseases. As you only desire information about influenza, we will leave all other fevers out of court and confine our remarks to influenza alone. Influenza is an epidemic, possibly infectious, disease, chiefly characterised by inflammation of the mucous membranes, and by the exceedingly formidable list of its sequelæ and complications. It is due to the multiplication within the body of a definite germ. The disease never occurs without this germ, nor is the germ ever found in the human body except in those who are suffering from, or who have lately recovered from, influenza. The great question of its causation is, “How does the germ gain entrance into the body?” And this unfortunately we cannot answer. It is not commonly an infectious disease in the usual meaning of the term—that is, it is not commonly caught directly from person to person; but we feel certain that one person can inoculate her fellow. The disease is epidemic, and spreads in waves which have usually swept from the east westwards. For this reason it has been suggested that the germs are conveyed from place to place by the east wind—an utterly untenable theory. Most probably the disease is spread by water, or by dust infected with the dried spittle of persons suffering from the disease. It is by no means a modern disease. There were epidemics of it in 1833, 1847, 1848, and 1888. Nearly all the epidemics have started in Russia, and hence the disease has been called Russian fever. When a person has had pneumonia following influenza, it imports that she has