The investigation of the causes of diseases has, probably more than any other department of medicine, been marked by belief without evidence, and assertion without facts. The history of the opinions which have at different times been so freely offered and adopted with regard to the production of leprosy, and the numerous explanations which have been proposed with respect to the causes of its almost epidemic prevalence in Europe in the middle ages, and its nearly complete suspension in the same region of the world at the present day, might easily, if time and space permitted, be made to form a chapter highly illustrative of the above general remark. The frequency of the disease in former times has been confidently ascribed by different authors[287] to peculiarities in the diet, dress, personal and domestic habits, etc., of our forefathers. And certainly their mode of life was in many respects specially calculated to generate derangements and eruptions of the skin. The good old Saxon practice of bathing[288] appears to have become forgotten after the date of the Norman conquest; and in the subsequent history of these early times we might trace various indirect and direct causes of cutaneous disease, in the close hovels and unventilated dwellings of the period;[289] in the habits of personal uncleanness;[290] in the rough straw bedding then generally[291] in use, and which “hard lodging” Hollinshed describes as still used by the servants in his day, “with seldome (he adds) anie sheete vnder their bodies to keepe them from the pricking straws that run oft through the canvas, and rase their hardened hides;”[292] and probably also in the articles of diet[293] on which the general community were obliged to subsist in times before the improvement of agriculture, and the introduction of that “schamefull intemperance” (as old Boece[294] fanatically terms it), “when na fische in the see, nor foule in the aire, nor beast in the wod may have rest, but are socht heir and thair to satisfy the hungry appetit.” For the investigation of this and other allied questions in the history of the production of our older epidemic and endemic diseases, the works of Hollinshed, Strutt, Henry, Chalmers, Macpherson, and others, contain a great and available mass of materials. But, in consequence of the unforeseen extent to which our present remarks have already lengthened out, we are forced to abstain from entering into this topic, and discussing the notes which we have collected in regard to it. At the same time, however, we may pause to observe that we believe it would be no easy matter to point out the exact differences in those physical conditions of the inhabitants of this country in former and in modern times, which may have led to the prevalence of the disease amongst our ancestors, and to its disappearance amongst us. If poverty in diet, or personal wants, and filth, and wretchedness in their deepest degrees, could generate the malady, there are certainly still numerous spots in continental Europe, and even in our own land, where, unfortunately, all these elements of disease are in our own day in full and active operation, without any such specific result following; the alleged causes are present without the alleged effects.
In order to attain anything like satisfactory results of the supposed physical causes of leprosy in Great Britain in former times, the whole question would require to be thoroughly investigated in connection with two others, viz., the allied physical circumstances,—firstly, of the inhabitants of those countries in which the disease in the same way formerly raged; and, secondly, of those districts of the world in which it is still prevalent. It is only by following such a line of inquiry that we could hope, if at all, to separate mere matters of opinion from matters of fact, and at last to obtain, by a kind of reasoning by exclusion, the exact physical condition or conditions of a people that are capable of originating or of spreading this particular species of disease. The difficulty of the problem may be easily appreciated by glancing for a moment at the diversified geographical localities and circumstances under which the tubercular leprosy is known at the present day to appear. In modern times it has been found existing, to a more or less limited extent, in places the most distant and the most dissimilar in regard to temperature, climate, situation, soil, etc., as in Sumatra,[295] under the equator, and in parts of Iceland almost within the verge of the Arctic Circle;[296] in the temperate regions of both hemispheres, as (in the southern) at Hamel en Aarde[297] in the Cape district, and (in the northern) at Madeira[298] and Morocco;[299] in the dry and arid plains of Arabia,[300] and in the wet and malarious districts of Batavia[301] and Surinam;[302] along the shores of Guiana,[303] and Sierra Leone,[304] and in the interior of Africa,[305] Hindostan,[306] Asia Minor,[307] and Asiatic Russia;[308] on the sea-coast, as at Carthagena,[309] and thousands of feet above the level of the ocean, as on the table-land of Mexico;[310] on some of the islands in the Indian,[311] Chinese,[312] Caribbean,[313] and Mediterranean[314] seas, and on the continents of Asia, Africa, and America.
Contagion as a Cause of Leprosy.
Most modern pathologists seem inclined to call in question the contagious nature of tubercular leprosy, as it at present exists in different parts of the globe.
Cullen, Darwin, and Good are almost the only English physicians of later times that have admitted the contagious character of the disease, and that not from personal observation. The evidence bearing against the doctrine of this mode of its diffusion is principally of a simply negative kind. In some of the districts in which the malady is endemic, the sick are seen to maintain a free intercourse with the healthy, without the disease being frequently or at all communicated to the latter; the nurses of the lazar hospitals are alleged to remain uninfected; lepers often continue long in the midst of their families without spreading the scourge to any of the other members; and occasionally a husband and wife are seen living in wedlock for years, one of them deeply affected by the disease, and the other remaining perfectly sound. Instances, exceptional to these general remarks, are certainly occasionally observed, as in a case quoted in a previous page from Dr. Kinnis, of a wife becoming infected subsequently to both her husband and daughter suffering from an attack of the malady. In such cases as this, however, we must recollect that the repetition of the disease in two or more members of the same family may merely depend upon the same external or general morbific agencies, acting upon the constitution of all the sufferers.
At least, whenever, from circumstances, this source of fallacy is avoided, the evidence of the contagion of leprosy seems to become more and more defective. Thus, when the disease happens to be imported in the person of an infected individual from a district in which it is endemic, to one in which it is unknown, the malady seems to have no tendency whatever at the present day to spread to any of the inhabitants of the new and healthy locality. Persons labouring under tubercular leprosy are occasionally, for example, sent from southern stations to England and France. In such not unfrequent cases the malady has never, I believe, been known to be communicated, in one single instance, from the infected person to those resident inhabitants of the new district, among whom he was living in free and daily intercourse.[315]
Did the leprosy extend and prevail over Europe in the middle ages as independently of propagation by contagion as the perpetuation of the disease seems to be in most localities at the present day?
If we deferred to the mere opinion of the older medical and historical authors, the contagious character of the disease at that era would appear to be undoubted. These authors express an unanimous opinion on its contagious propagation; and it is not till we come down to the professional writers of the seventeenth century, as Fernelius[316] and Forestus,[317] that we find this doctrine ventured to be called in question.