and the prevalence of the pestilence in all diversities of soil as well as of climate is scarcely compatible with the hypothesis of its subterranean evolution.

The electric theory, which has at present many zealous champions, is evidently inadmissible as an explanation of phenomena which have been developed under all possible fluctuations of the atmospheric electricity, as well as during its undisturbed equilibrium. The meteorological reports of the last few weeks are, indeed, sufficient of themselves to refute such an hypothesis. We find the air returned, on successive days, as electro-positive, electro-negative, and neutral; with a tension sometimes weak, sometimes strong, sometimes variable, sometimes null; while the phenomena of cholera, during the same period, have exhibited no corresponding fluctuations.

The ozonic theory, which has been recently started, attributes cholera to an alleged deficiency, and influenza to an affirmed excess of ozone in the atmosphere. Ozone is a volatile product, composed, like water, of hydrogen and oxygen, but having an extra dose of oxygen. Schönbein ascertained that it is developed during the working of an electrical machine; and it is said to be produced naturally in the air, by an unexplained action of the atmospheric electricity on moisture. This ozone has the property of oxydizing and so deodorizing all putrescent exhalations, and, besides its purifying effect on the air, it is supposed to promote the decarbonization of the blood in the lungs, and to stimulate by a free supply of oxygen, the performance of the vital functions. When ozone is deficient, it is said the blood remains unrelieved of its carbon-the organs of secretion, deprived of their natural stimulus, cease to act—the air becomes loaded with putrescent exhalations— in a word, all the conditions of cholera are fulfilled, and an epidemic outbreak ensues. A superabundance of ozone, on the other hand, is supposed to irritate the mucous lining of the respiratory organs, and so to produce epidemic catarrh. Birmingham, according to this theory, escapes cholera because its great fires generate ozone, and thus artificially make good the deficiency in the natural supply. London has suffered from cholera because (according to Quetelet) during three months past the electric tension has been low and the supply of ozone consequently defective. This statement is made on M. Quetelet's authority. Dr. Moffat, on the other hand, is said to have ascertained experimentally an excess of ozone, due to a corre. sponding elevation of electric tension, during epidemic influenza.

This hypothesis is ingenious, and may usefully engage the attention of experimentalists. So far as we can yet judge, it seems to rest on assumption, and to afford explanations alike inconsistent with recorded facts. A glance at the meteorological returns will show that cholera has co-existed with excess as well as deficiency of atmospheric electricity, and consequently also of atmospheric ozone. It has ravaged one town, and spared another in its immediate vicinity (Moscow, &c., for instance), though plunged in the same atmosphere, Birmingham, with its alleged excess of ozone, is not, as it should be, the permanent seat of influenza, and the towns situated amidst the great blast furnaces of Shropshire (Wednesbury, Oldbury, &c.), so far from participating in the immunity of Birmingham, have, on the contrary, been decimated by the epidemic.

The theory of a specific volatile poison, reproduced, like the smallpox virus, in the body of each cholera patient, has been, and still remains, the subject of vehement controversy. It is deeply interesting, because it involves the grave questions of contagion and quarantine, and because much weighty evidence and many eminent names are arrayed on both sides of this argument.

The advocates of this theory mainly rely on the facts, that cholera is observed to travel along roads, rivers, and all the great channels of human intercourse; that it has often broken out in camps immediately after the arrival of infected battalions; in armies, after a battle with infected adversaries; and in towns, after the arrival of infected individuals. They bring forward long series of affiliated cases, in which the seizure of each victim is traced backward to communication with a previous sufferer as its cause. They adduce a number of cases to show that the attendants on the sick suffer in a greater proportion than the rest of the population; and they produce examples of convents, foundling hospitals, and other institutions, which, though standing in the heart of cities ravaged by cholera, have yet by a strict isolation, entirely escaped infection. To the objection, that thousands upon thousands of persons have held close intercourse with the sick without taking the distemper, they reply that in such cases the requisito predisposition was wanting.

Their opponents, on the other hand, allege that towns lying in the track of the pestilence, and communicating freely with infected districts, frequently escape if airily situated and well drained; that whole countries (Hanover for instance) have enjoyed almost entire

immunity without employing quarantine-while others, such as Austria and Prussia, suffered in spite of military cordons and the most rigorously enforced isolation. They bring forward numerous instances of infected troops joining healthy encampments without communicating the disease; and equally numerous cases of pestilential outbreaks in healthy regiments on their encampment in low marshy districts, and without any arrival amongst them of infected persons. The alleged mortality amongst the attendants on the sick they declare to be exceptional; and they bring forward an overwhelming mass of evidence from all quarters of the globe, to show that the physicians and nurses in cholera hospitals do not suffer in a larger than the average proportion. The immunity enjoyed by certain convents, foundling hospitals, &c., they attribute not to their isolation, but to the regular life and diet of the inmates, and to their superior sanitary condition. And they argue justly, that to ascribe to a lack of predisposition the escape of the hundreds of thousands who have communicated with the sick without taking the disease, is a mere petitio principii.

So stands this momentous question. Scientifically considered, it appears hardly susceptible of a rigorous solution. Every case of seizure following on communication with an infected person may be met with a case, equally authentic, of seizure following on arrival in an infected place, or on respiration of contaminated air. On the other hand, every case of escape, nothwithstanding exposure to effluvia emanating from the sick, may be counterpoised by equivalent instances of escape, notwithstanding residence in a contaminated district or immersion in a contaminated atmosphere. The rejoinder, founded on a presumed lack of predisposition in the individual exposed, is equally available on both sides of the question; nor can it ever be certainly known with respect to either of the assigned causes of infection, whether it did or did not co-operate with some other; nor to which of several influences, all possible, perhaps all co-existent, the observed effect is due.

Practically, however, the question is conclusively settled in the noncontagionist sense. The experience of our own hospitals and hospital ships (especially of the Dreadnought and the Dover) has proved that the physicians and nurses of cholera patients are not more liable to the distemper than persons not so engaged. And the experience of Naples, Vienna, Moscow, and other continental towns, has proved,

beyond dispute, the utter inefficacy of quarantine regulations to repel epidemic invasion.

The theory next in order to be noticed is that which seeks to connect cholera with the putrescent emanations of sewers, graveyards, &c., not merely as predisposing influences, but as actually containing the specific volatile cause of the disease. For such an hypothesis we can find no solid foundation. It cannot even be shown that the typhus infection itself depends so directly, as these theorists affirm, on putrescent animal effluvia; for typhus fever is unknown between the tropics, though putrescent exhalations are abundant in those latitudes. Moreover, anatomical students, who pass month after month in the dissection of decaying bodies, though weakened sometimes, are not observed to be fevered by the stench. And M. Thouret records that, when the putrescent accumulations of many years were removed, in 1786, from the churchyard of St. Innocens at Paris, no febrile disorder was produced among the workmen engaged in that loathsome operation. They suffered nausea, loss of appetite, debility, tremor-sometimes even asphyxia; but not one of them was attacked either with typhus or cholera. Putrifying animal emanations must therefore be held to predispose the body for typhus or cholera, only as they predispose it for small-pox, for dysentery, for influenza, or for the plague. Of this we have conclusive evidence in the fact that, amongst the persons exposed to putrescent effluvia in the crowded quarters of Gibraltar, black vomit prevailed in 1828, cholera morbus in 1834, and typhus fever in several previous and subsequent years; while, again, the close districts of the towns in Malta were ravaged in 1813, by the plague; in 1833, by influenza; and in 1837, by Asiatic cholera.

Such are the principal theories by which it has been sought to explain the genesis of Asiatic cholera. Each keeps in view one aspect of the question, but errs in neglecting the others. Each affords a hypothetical explanation for a certain number of the facts, but fails in its application to the remainder. Nor would either of them, even if established, afford the least clue to that inscrutable mystery-What is the agency or influence by which, in cholera, the vital force is subdued?—what is it, and how does it, operate?

But though the cause of cholera eludes our limited means of investigation, sensuous and intellectual, its conditions of existence

are ascertainable; and its fixed relations to age and sex, to class and diet, to certain bodily organs, and to certain remedial agents, have been and at this moment continue to be, the subject of patient and exact observation. The latest researches exhibit the disorder as more fatal in infancy and old age than in the prime of life; as attacking both sexes in nearly equal proportion; as chiefly ravaging the poor and ill-fed classes; as rarely seizing the wealthy and robust, except when errors of diet or irritation of the intestinal membrane have placed them on a par for the time (so far as this disease is concerned) with organisms of inferior resisting power. The poison, moreover, has a period of latency which rarely exceeds three days, and never a week; so that after this interval a person who has been exposed to contamination may consider his risk at an end. It can, however, co-exist with other diseases in the body; so that persons labouring under consumption, syphilis, typhus, small-pox, &c., do not, as it has been erroneously asserted, enjoy immunity from cholera. The disorder rarely attacks the same individual twice, though cases of re-seizure are recorded, and relapses during convalescence are even frequent. The mortality amongst the smitten varies with the period of the epidemic. At its first outbreak in Moscow nine-tenths of the cases proved fatal; as the season advanced this frightful mortality gradually diminished, till towards its close the original proportion of deaths to recoveries was reversed. The organic seat of the disease appears to be the lining membrane of the intestines, which after death has been usually found more or less disorganized. But this local disorder is accompanied by a violent exhaustive impression on the nervous system, analogous to that produced by a large dose of arsenic or other deadly poison. For the cholera virus, once fairly absorbed in the system, no antidote is known; nor can the vital power be assisted in its desperate struggle with the poison by any treatment yet discovered. The most powerful narcotics, astringents, and stimulants; bleeding and injection of blood; heat and cold, even in the extreme forms of fire and ice; galvanism, acupunctuation, and the respiration of various gases; all the neutral salts, all the acids and alkalies, all the mineral and vegetable poisons-have been tried without success. Under twenty plans of treatment pursued in twenty hospitals at Moscow, the average mortality was found to be the same; nor did those who obtained no medical aid at all die in a larger pro portion than the rest.