Let us add to this, that the meat diet of the poorer class, whether serfs or freemen, would be apt to consist of the more worthless portions, the semi-putrid pieces in the salted sides of bacon, mutton or beef, and that badly-cured pork was in many parts the usual kind of flesh-food; and we shall have no difficulty in finding the noxious element in the diet of the Middle Ages, which the dietetic hypothesis of leprosy requires. Some who have advocated that hypothesis for modern leprosy, have laid themselves open, notwithstanding the ability and industry of their research, to plausible objections which have no bearing if the hypothesis be sufficiently safe-guarded. Leprosy, like every other _morbus miseriae_, needs a number of things working together to produce it, its more or less uniform specific character or distinctive mark being determined by the presence of one factor in particular. The special factor should be generalised as much as possible, so as to cover the whole circumstances of leprosy: it is not only half-cured or semi-putrid fish[208], but half-cured or semi-putrid flesh of any kind. The most general expression for leprosy is a semi-putrid or toxic character of animal food, just as for the allied pellagra, it is a semi-putrid or toxic character of the bread or porridge. Moreover it is that noxious or unnatural thing in the food, not once and again, or as a _bonne bouche_, but somewhat steadily from day to day as a chief part of the sustenance, and from year to year. As the rain-drops wear the stones, so the poison in the daily diet tells upon the constitution. Once more, such special causes may be present in a country generally, among the poor of all the towns, villages and hamlets, and yet only one person here and there may show specific effects that are recognisable as a disease to which we give a name. Unless there be present the aiding and abetting things, the special factor will hardly make itself felt; and if there be not the special factor, there may be some other _morbus miseriae_ but there will not be that one. These aiding things are for the most part the usual concomitants of poverty and hardships, wearing out the nerves far more than is commonly supposed and producing in ordinary an excessive amount of nervous affections among the poor. But among the poor themselves, as well as among the well-to-do, there are special susceptibilities in individuals and in families. One person may have the same unwholesome surroundings as another and the same poisonous element in his diet, but he may fall into no such train of symptoms as his leprous neighbour because he is not formed in quite the same way, because he has “no nerves,” or is of a hardier stock, or because his unwholesome manner of life comes out in some other form of disease (scrofula perhaps, less probably gout), or for some other reason deeply hidden in his ancestry and his personal peculiarities. The chances would be always