Part 9

It appears that there are still inhabited places in which the Chinese compliment on the serpents might be added to that of the mosquitoes.

Proportionate to this prodigality of organic life is the amount of organic decomposition, the products of which are poured into the atmosphere and suspended in the surrounding vapour and fog, to which they give a decided and often a highly offensive odour.

Footnote 11:

See note, p. 16.

“On fixing our eyes on the tops of the trees,” describes Humboldt, “we discovered streams of vapour wherever a solar ray penetrated and traversed the dense atmosphere, exhaling, together with the aromatic odour yielded by the flowers, the fruit, and even the wood, that peculiar odour which we perceive in autumn in foggy seasons. It might be said, that notwithstanding the elevated temperature the air cannot dissolve the quantity of water exhaled from the surface of the soil and of the vegetation.”

“At the distance of several miles from the coast,” says Dr Daniell, in describing the western shores of Africa, “the peculiar odour arising from swampy exhalations and the decomposition of vegetable matter is very perceptible, and sometimes even offensive. The water also is frequently of a dusky hue, with leaves, branches, and other vegetable debris floating on the surface, brought down from the interior by innumerable narrow channels that empty their turbid streams into the open ocean.”

It is under these climatic conditions that the worst forms of epidemics are engendered: the most sudden in their attack, the most rapid in their development, the most general in their prevalence, and the most mortal.

The form of the epidemic prevalent in any particular district is dependent on the physical characters of the immediate neighbourhood. Thus intermittents prevail chiefly in marshy and swampy districts: remittents also chiefly there, though not exclusively; while in other localities other forms arise approximating to the continued type of temperate climates.

For the most part these epidemics are strictly endemic, and are confined to the particular regions in which they are engendered. They never pass the limit of the equatorial or tropical zone. Yellow Fever, one of the most common and destructive of these diseases, is still more restricted in its range, being confined within a definite line determined by temperature. It is incapable of existing where the average range of the thermometer is greater than from 76° to 86° of Fahrenheit, or where the temperature varies more than from 5° to 10° night and day. Extreme heat and moderate cold immediately stop it; nay, even the prevalence of a cold wind for a few hours only.

In other instances these epidemics pass beyond the regions in which they are produced, and sometimes extend to all the other quarters of the globe. The Black Death, the range of which we have seen, was engendered in China; the Cholera of our own day, generated in the delta of the Ganges, the great source and centre of Indian epidemics, ravaged that country long before it directed its course to Europe.

When these tropical epidemics advance into more temperate climes, they lay aside nothing of their nature; they lose but little of their power. Wherever they go they decimate the populations which they attack.

One remarkable peculiarity of some of these epidemics is, that natives of the region in which they prevail are for the most part unsusceptible to them. This is true however only of particular forms of pestilence. Some of them acknowledge no acclimation. Cholera, for example, attacks equally natives and new comers. On the other hand, yellow fever rarely attacks the natives who reside permanently within its zone. Its chief victims are strangers who have recently arrived within its sphere, particularly the inhabitants of northern climates. The susceptibility to its influence appears to be strictly proportionate to the degree of northern latitude from which the stranger has arrived, and the shortness of the interval that has passed since he left the European for the Equatorial regions.

We see something of the same kind in the wide-spread epidemics of our own country. During the prevalence of Cholera it was observed over and over again, that persons coming directly from the pure air of the country into the infected part of a town, were seized with the disease. The explanation is not obvious. It would seem, however, to be connected with the suddenness of the shock on the system. Priestley found, that after shutting up a mouse in a given quantity of air a considerable time, it seemed to be weak, and to be slowly dying. If at this period he put a fresh mouse into the same air, it instantly died. It seems as if the system can bear a pestiferous atmosphere better when gradually than when suddenly exposed to it.

I do not know that I can give a more vivid picture of a tropical epidemic than that which is afforded by the outbreak of Cholera in the 86th regiment at Kurrachee in June, 1846.

On this occasion the atmosphere was very peculiar,—damp, hot, stagnant, and oppressive. Not a breath of air was stirring. A few isolated cases of cholera had occurred for some days. The utmost alarm was excited in the minds of experienced persons, who felt certain that an epidemic was at hand. Their fears were too fully realized. On the night of the 15th, upwards of 40 men were seized with cholera in its severest form; in two days more 256 were attacked, of whom 131 were already dead.

“The floors of the hospital,” says Dr Thom, the surgeon of the regiment, “were literally strewed with the livid bodies of men labouring under the pangs of premature dissolution. Many were brought in with the cold and clammy damp of death; as if sudden obstruction of every vital function had taken place, and the fountains of life had been arrested by an invisible but instantaneous shock. It was indeed a sight never to be forgotten, to behold the powerful frames of the finest men of a fine corps, who had that morning been in apparent good health, and most of them on the evening parade, as if at once stricken down, and striving, with the last efforts of gigantic strength, to resist a death-call that would not be refused.”

In describing a river on the west coast of Africa, Dr Daniell says—“When I visited it, I found two vessels moored a short distance from its mouth, one of which within the space of five months had buried two entire crews, a solitary person alone surviving. The other, which had arrived at a much later period, had been similarly deprived of one-half of its men, and the remainder were in such a debilitated condition as to be incapable of undertaking any active or laborious duty. Immediately before, another vessel had sailed from this port in such a deplorable state as to be solely dependent on the aid of Kroomen to perform the voyage.”

In the statistical report of Sir Alexander Tulloch it is stated, that out of 1658 white troops sent out to military stations on the western coast of Africa, 1271 perished from climatic diseases; while of the 387 who remained to be sent home, 17 died on their passage; 157 were reported as incapable of further service; and 180 as qualified only for garrison service; thus leaving only 33 out of 1658 men who were fit for active service.

As we pass out of the torrid zone a remarkable change takes place in the general character of epidemics. They lose more and more of their intermittent type, and become either remittent or continued. The remittent keeps its hold over the southern part of Europe, and continually breaks out in the form of Yellow Fever. As we proceed northward out of the yellow fever zone, that disease wholly disappears, and typhus and its kindred maladies take its place; typhus commencing precisely at the point where yellow fever ends.

There is, indeed, one of the ordinary diseases of temperate climes, and only one, which appears capable of penetrating within the torrid zone, and of committing greater ravages there than in lower temperatures, and that is Small-pox. With this exception, the ordinary epidemics of temperate climates do not enter the tropics, while, on the other hand, the ordinary epidemics of the tropics every now and then decimate the temperate regions.

“In these our latitudes,” says Dr William Fergusson, “cold and fatigue, and sorrow and hunger, will generate fever anywhere; but every region, every climate, will exhibit its own form of fever. With us it is Typhus; in the warmer countries of Europe, Remittent; in the upper Mediterranean, Plague; in the Antilles and Western Africa, Yellow Fever; this last being restricted to particular localities, temperatures, and elevation. While typhus fever goes out when you enter the tropics, it is there that yellow fever commences; the pure epidemic of a hot climate that cannot be transported or communicated upon any other ground. Places, not persons, constitute the rule of its existence. Places, not persons, comprehend the whole history, the etiology of the disease. Places, not persons! Let the emphatic words be dinned into the ears of the Lords of the Treasury, of Trade and Plantations, until they acquire the force of a creed, which will save them hereafter from the absurdity of enforcing a quarantine in England against an amount of solar heat of which its climate is insusceptible. Let them further be repeated in the Schools of Medicine until the Professors become ashamed of imbuing the minds of the young with prejudice and false belief, which, should they ever visit warmer climates, may cause them to be eminently mischievous in vexing the commerce and deeply and injuriously agitating the public mind of whatever community may have received them.”

Footnote 12:

See Cases of the Eclair, Dygden, &c., post.

Climate differs not only in different countries but in different parts of the same country. The climate of the country is different from that of the city. The climate of every city, town, and village, differs from that of every other. The temperature, the moisture, and the other meteorological conditions of different districts, nay, even of different streets in the same town, vary to such a degree as to influence materially their relative salubrity and the prevalence or absence of particular classes of disease. These local climatic conditions and their connection with prevalent diseases, have not as yet received due attention: when they shall have received it—and they will receive it—a new light will be shed on local epidemics.

* * * * *

I pass now to CIVILIZATION.

We have no sufficient knowledge of the state of the people and of their diseases, in any of the civilized nations of antiquity, to trace the relation between them. The authentic history of periods, comparatively near to our own time, as far as concerns the diseases of the people, goes scarcely further back than the 14th century. The first great epidemic, to which I have so often called attention, occurred in that century, and we have reliable evidence, both of the phenomena attending this plague and the condition of the people at that time. I assume this period therefore as my starting-point.

I take a civilized community to be one in which there exist—