1733. There is nothing to note between Boyle and Arbuthnot; for Willis

and Sydenham, using the Hippocratic language of “constitutions,” explained, as we have seen, the epidemic catarrhs of the spring or winter as the reigning febrile constitution modified to suit the season and weather. Arbuthnot’s essay makes more modern reading than Boyle’s. He assumes emanations from the ground, but they are no longer from the bowels of the earth, or from deposits of strange minerals requiring earthquakes to set them free, or “fire and menstruums” to give potency to them. Of all the things that pass into the atmosphere, he makes most of the various steams and other volatile decomposing matters of men and animals; and when he brings in the earth, it is as the storehouse or receptacle of such matters, in a surface stratum no deeper than the effects of drought and rainfall could reach. While he accepts the Hippocratic doctrine of epidemic constitutions, and recognizes the air with its various organic contents as the τὸ θεῖον, the _quid divinum_ or mysterious something of epidemical causation, he does not forget that the earth is inhabited by creatures, human and other, who befoul the atmosphere by “their own steams”; again, he lays stress upon alternations of drought and moisture in the soil and subsoil as a cause of morbific emanations, not, indeed, stating the matters of fact in the very terms of Pettenkofer’s law, but assuming the presence of special organic matters in the soil as much as that does. Although Arbuthnot was hardly a serious epidemiologist, any more than Boyle, yet in the growth of opinion on the subject of morbific matters in the air, he may be said to have shifted the interest from inorganic or mineral substances and gases, to organic matters chiefly of human or animal origin, and from the deeper regions of the globe, such as only earthquakes reach, to the surface stratum of soil and subsoil which is affected by every rise and fall of the ground-water. I shall now give a few extracts, to bear out the above summary, from Arbuthnot’s essay. “Air,” he says, “is the τὸ θεῖον in diseases, which Hippocrates takes notice of. Air is what he means by the powers of the universe, which, he says, human nature cannot overcome; and he lays it down as a maxim ‘that whoever intends to be master of the art of physick must observe the constitution of the year; that the powers and influence of the seasons (what are seldom uniform) produce great changes in human bodies.’” He then pays a compliment to Sydenham as “endowed with the genius of Hippocrates,” and passes on to his own analytic method. “Many great effects must follow, and many sudden changes may happen in human bodies by absorbing outward air with all its qualities and contents. Nothing accounts more clearly for epidemical diseases seizing human creatures inhabiting the same tract of earth, who have nothing in common that affects them except air: such as that epidemical catarrhous fever of 1728 and of this present year [1733].... It seems to be occasioned by effluvia, uncommon either in quantity or quality, infecting the air.... It is likewise evident that these effluvia were not of any particular or mineral nature, because they were of a substance that was common to every part of the surface of the earth: and therefore one may conclude that they were watery exhalations, or, at least, such mixed with other exhalable substances that are common to every spot of ground.” In his account of the qualities and contents of the air, he enumerates them, not so much as detected in the air on analysis, but as having of necessity passed into it, and in some instances been deposited again from it, as in strange dews. One class of substances that pass into the air are the oils, salts, seeds and insensible abrasions of vegetables. Also all excrements and all the carcases of animals vanish into air. Another ingredient of the air is the perspirable matters of animals, the amount of which for human beings he works out by a curious calculation of a column of their own steams raised so many feet high in so many days. Perhaps there are insects in the air invisible to human eyes: one may observe, in that part of a room which is illuminated with the rays of the sun, flies sometimes darting like hawks as if it were upon a prey. Some have imagined the plague to proceed from invisible insects: this system agrees with many of the appearances in the progress or manner of propagation of that disease, but is altogether inconsistent with others. Air replete with the steams of animals, especially such as are rotting, has often produced pestilential fevers in that place: of which there are many instances. But why should certain years or seasons have a pestilential atmosphere, for example the season of the catarrhous fever of 1733? There had been, he says, an unusual drought for these two years past, the best estimate of the dryness of the surface of the earth being taken from the falling of the springs, “the consequence of which has been unusual diseases amongst several animals, and a great mortality amongst mankind. It is true, this did not happen during the dry weather.... The previous great drought must have been particularly hurtful to mankind. Great droughts exert their effects after the surface of the earth is again opened by moisture, and the perspiration of the ground, which was long suppressed, is suddenly restored. It is probable that the earth then emits several new effluvia hurtful to human bodies: this appeared to be the case by the thick and stinking fogs which succeeded the rain that had fallen before.” Arbuthnot knew the progress of the influenza of 1732-33. Its worst week in London was from the 23rd to the 30th January, 1733; but he tells us that it had been at a height in Saxony from the 15th to the 29th November, 1732, had been earlier in Holland than in England, earlier in Edinburgh than in London, in New England before Great Britain. Again, it appeared in Paris in February, somewhat later than in London, and in Naples in March. This progress, he says, was often against the wind. Nor does he assume a progressive infection of regions of atmosphere. The effluvia, he says, were of a substance that was common to every part of the surface of the earth; they were exhalable substances that were common to every spot of ground; the excessive drought of two years, followed by heavy rains in the end of 1732, is also assumed to have been common, for, in Germany and France, especially in November, 1732, the air was filled with frequent fogs. It is clear that Arbuthnot traced the universality of influenza, the uniform symptoms of which he recognized, to certain conditions of soil and atmosphere common to all the countries visited by the epidemic. Throughout the rest of the 18th century there were numerous and varied experiences of influenza, in summer and winter, spring and autumn, coming up from the south as if from Africa, or from the east as if from Central Asia, or appearing in America sooner than in Europe--experiences which made a theory of the disease difficult. Some inclined to Arbuthnot’s view of unusual seasons and weather producing the same effects everywhere; others favoured the hypothesis of contagion from a remote source, which might be China or might be some other territory. Geach, a surgeon at Plymouth who was a Fellow of the Royal Society, actually went back to the astrological cause, pointing out that Jupiter and Saturn were in a certain conjunction during the influenza of 1775. The only elaborate theory of the strange disease that calls for notice, besides those of Boyle and Arbuthnot, is that of Noah Webster, the famous lexicographer of Hartford, Connecticut. While Webster was a journalist in New York about the years 1794-6, the subject of yellow fever, which was then of great practical moment, set him reading and speculating about pestilences in general. Writing to Priestley, he said that in the course of his inquiries he found the American libraries ill supplied with books[755]; but he certainly made diligent and skilful use of his literary materials, and produced in his ‘Brief History of Epidemic and Pestilential Diseases,’ a work which was better than any before it in the chronological part, and remains to the present time unique in its philosophical part for the boldness of its generalities[756]. He saw that influenza was the crux of epidemiology, and paid special attention to it. In looking for the antecedents of influenza, he kept in view the greater telluric changes and convulsions, such as earthquakes and volcanic eruptions. He did not regard these as the cause of influenza, but as the index of some hidden cause to which both they and the universal catarrh were due. “It is probable to me,” he says, “that neither seasons, earthquakes, nor volcanic eruptions are the causes of the principal derangements we behold in animal and vegetable life, but are themselves the _effects_ of those motions and invisible operations which affect mankind. Hence catarrh and other epidemics often appear _before_ the visible phenomena of eruptions and earthquakes[757].” As to influenza, he found “reason to conclude the disease to be the effect of some access of stimulant powers to the atmosphere by means of the electrical principle. No other principle in creation, which has yet come under the cognizance of the human mind, seems adequate to the same effects.” And again: “It is more probable that it is to be ascribed to an insensible action of atmospheric fire, which is more general and violent about the time of eruptions, and which fire is probably agitated in all parts of the globe, although it produces visible effects in explosions in some particular places only.” It is due to Webster to give his reason for preferring a physical force to an organic poison: “If a deleterious vapour were the cause, I should suppose its effects would be speedy, and its force soon expended, the atmosphere being speedily purified by the winds. But if stimulus is the cause, it may exist for a long time in the atmosphere, and the human body not yield to its force in many weeks or months. This would better accord with facts. For, although diseases appear soon after an earthquake, yet the worst effects are often many months or years after[758].” Dr Blagden also saw a difficulty in “the prodigious quantity of matter required in the air to infect the space not only of the Chinese land, but to a hundred leagues of the coast, or, as in this instance [1782] all Europe and the circumjacent sea,” and was accordingly driven to Arbuthnot’s view of an origin in the unusual weather of each locality. Webster drew up a chronological table of influenzas in either Hemisphere, with the volcanic eruptions, earthquakes, comets, etc., to suit[759]. A few instances from near the beginning may serve as samples: