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.