As we have already noted, we found in the examination of an excised piece of a recent eruption, in a nodular case of leprosy, chiefly, round cells surrounding dilated vessels, and only after long search, a few bacilli. It thus appears not improbable that during the eruption a toxin (which is circulating in the blood), and only a few bacilli, escape from the vessels at various places, or, it may be, only the bacilli, which produce the toxin locally; that further, the toxin causes the emigration of white blood corpuscles, and that the escaped bacilli only after some time slowly increase in number and gradually fill the cells. From the presence of the bacilli in the endothelium of the vessels and in the connective tissue cells, one may speculate that the bacilli are passively forced into them by the blood or lymph pressure; we have certainly found, in the testicle referred to, bacilli free between the red blood corpuscles in the vessels (_Plate X, Fig. 7_). Such a fresh eruption may remain stationary or slowly develop into a nodule, or it may apparently completely disappear, and only after several years again become apparent, it may be during a fresh eruption. We fancy that in these cases a few bacilli are deposited at the time of the first eruption, and that they have needed years to become so much increased that a permanent nodule has finally formed. That the vessels receive lasting injuries from the leprous infection, appears to us to be proved by the following observations. In an epidemic of measles in one of our institutions, we saw in anæsthetic patients the previous leprous spots, which had long disappeared from view, definitely reappear, the _hyperæmia_ and turgescence being on these places general, so that the earlier spots stood out as well defined, red, and somewhat swollen areas. All this appears to point to the fact that the bacilli increase very, very slowly, and that possibly they also produce a toxin, usually only in small quantities, which causes no particular injury to the organism, since the patients, in spite of numerous nodules, with millions or milliards of bacilli, may remain in pretty good health for years. We may also conjecture that the toxin which is produced, usually only acts immediately around the bacilli, leading to dilatation of the vessels and favouring the migration of white blood corpuscles. Only occasionally does the production of toxin or the multiplication of the bacilli appear to become so vigorous that toxin and bacilli get into the blood and cause an eruption; possibly this is favoured by peculiar anatomical conditions, for it is very striking with what varied frequency eruptions appear in different patients. That the bacilli in the nodules are all of them dead, as has been assumed, we cannot admit, so long as the nodules still grow. It appears to us preferable to ascribe the character of the disease to the relative benignancy and slight viability of the bacilli, as Unna has already suggested. As we