revived hypothesis now as generally accepted, as if it were gospel truth. All I can say respecting it is, that if influenza be dependent on a germ or microbe, then every common cold a person takes is dependent on the same or a similar cause, for in every particular the taking of a common cold and the taking of influenza are identical except in matter of degree. In both a disturbance in the nervous system is the primary cause of the symptoms, and in both the course which the symptoms take depends on the impression of the first nervous shock. But those who are very susceptible to colds know perfectly well that they can give themselves a cold at any moment they choose. A sudden change of garments will suffice to produce the affection; sitting in a draught of air passing through a chink or a keyhole will do it; getting wet in the feet will do it; sudden change of air will do it; whilst anything that reduces the nervous tone will intensify the danger of each or any of these exposures. In childhood the susceptibility to colds is infinitely less than it is in advanced age, and is also less in men who are inured to cold and wind, like drivers of railway engines. On the other hand, those who, being accustomed to live in close, warm air, are suddenly exposed to damp or cold air; those who are always changing from shelter to exposure, like railway porters; those who have to walk about in the cold and damp and are subjected to considerable muscular fatigue, like policemen and postmen-those all are liable to colds, and in similar manner are liable to influenza. Influenza, in a word, is, as the older physicians said it was, "an epidemic catarrh." If a catarrh is infectious or contagious, influenza is, and the evidence in favour of infectiousness or contagiousness is the same in both affections. A cold or catarrh runs sometimes through a house. Is that evidence of contagion? Influenza, or

acute epidemic neuroparesis, stands in the same doubtful position.

As we reflect on the phenomena of catarrh and influenza, there come forcibly before us two elementary questions which through all the long ages of physic have never yet been solved, although the facts that give rise to them have so long been under review.

The first of these questions is: What is a catarrh ? It is a nervous disorder, a nervous shock or depression, a neuroparesis followed by pyrexia. But what is the reason of it? A man takes or catches cold. Why? He passes through a certain well-known series of changes from natural function and then recovers. Why? If we could solve this one primary and simple question influenza would be no mystery. Colds are the origins of three-fourths of our acute diseases; they are constantly under our observation; they attack individually; they attack endemically; they attack epidemically; they leave different trains of disease; they specially afflict some persons; they let others go free. Why? It is mystery. All we can say is that a cold is the effect of some untoward impression carried from the peripheral nervous expanses to the centres, and that the further phenomena are reflexes from the centres. We are accustomed to assume that the respiratory mucous surface is the surface first attacked or impressed, and often it is so. But the rule is not universal; if it were why do wet feet cause the primary phenomena ? Why does exposing one-half of the body to colder air than the other half do the same thing? Why does exposure of the loins to extreme cold do the same, with special tendency to reflex rheumatic symptoms?

The second question of moment relates to the physiology of contagion. To believe heartily in what may be called a specific blood or fermentative contagion, a contagion

in which, as in small-pox, some material thing is carried from one living body to another living body, and multiplies by contact diffusion, is at present the humoral and accepted doctrine. But is this altogether correct? Is there not such a thing as nervous contagion, contagion of sympathy, contagion through the senses and the common sensibility, which, though infinitely more subtle than humoral contagion, is far more pervading and infinitely more active? I have myself no doubt on the matter, and I strongly suspect that the humoral contagions themselves may have their original start from such nervous source. In this sense catarrh and influenza, and neuropareses generally, with their sequælæ, may become contagious through susceptible natures, just as in panic when one bearer of terrible news, stricken with fear, infects another or others with his symptoms until a veritable endemic or even epidemic of fear and faintness is the communicated and communicating catastrophe, before which persons of the weakest nervous organisation, the nervous and jaded, are the first to succumb.

OPUSCULA PRACTICA.

"There are mites in science as well as in charity."

BENJAMIN RUSH.

DRY AND MOIST FOGS.

HE symptoms complained of from fog differ much according to individual constitution and age. During the recent fogs in London I have inquired very carefully into the matter, and have tried to discover if there are any particular symptoms which admit of being grouped together under distinct forms of fog. To some extent it may, I think, be admitted that groupings are possible; but the distinctions are not peculiarly clear, if the term "fog" be not itself in each case defined. The character of the fog makes a decided difference.

Some fogs are moist; some are dry. On the day when I am writing this article-January 24th, 1892-we have in the part of London where I reside (Manchester Square) a dense fog; but although I am unable to move from one room to another without the aid of artificial light, the hygrometer in my library records only 38 degrees of moisture in the air, and the barometer is at 30. This therefore may be called a dry fog; it is unpleasant, and it must be unhealthy, but it is not particularly chilling. The symptoms arising from such a fog are those of nervous irritability without feverishness and without unusual depression. I do not notice

that they who are sick are very much injured by the fog, nor are they peculiarly depressed by it; those who have bronchial disease are most affected locally, and they not so much as might be expected. The healthy complain variously. One says the fog renders the eyes irritable and causes a free secretion of fluid, with constriction about the forehead and a sense of weight in the head, but without actual catarrh. Another complains of constriction and dryness of the mucous membrane of the fauces, with an extension of the same along the bronchial tract, and with a certain amount of constriction of the chest. A third is conscious only of muscular weakness. A strong middleaged man says he feels "as if he were drawn by a magnet whenever he seats himself in a chair ; the chair, that is to say, seems to draw him to itself; and when he lies down in bed he feels as if all his body were drawn earthwards in a similar manner. In plain language, the fog makes him physically feeble. On the other side I have found some persons who, although advanced in life, are in excellent condition, and say they feel in good spirits, but regret they cannot, because of the darkness, get out of doors for exercise with their usual facility. I notice now also, as I have noticed in previous conditions of a similar character, that no great excess of catarrh, rheumatism, or neuralgia prevails. One, all but confirmed, rheumatic sufferer, under my frequent observation, is at this moment freer from pain and more active than she has been for many years past.

Those who have chronic bronchitis or asthma during dry fog with a high barometer suffer from irritation. in the bronchial passages, and expectorate a secretion which for colour almost approaches soot-black. They