These two cases have been considered by some as all but decisive of the question; they have been looked on as furnishing cumulative proof of the self-propagating power of cholera. But to satisfy others, especially those gifted with only a moderate share of credulity, it would be necessary to show that there was not at the time an endemic cause of cholera on the banks of the Thames, which, though then but sparingly developed, was capable of exciting the disease in persons strongly disposed to it, by previous disease, destitution, or other debilitating agents. It would be necessary to show that one of the laws of other febrile endemics, such as yellow fever, does not influence this, namely that when the _essential_ cause is in much force it attacks persons, though with a certain relation to individual susceptibility, with various degrees, up to the least conceivable degree of it; while reversely, when the cause is little diffused or concentrated, only those who are especially disposed to it—only those who have excessive susceptibility, natural or acquired—constitutional disposition, or disposition from circumstances of life—suffer from it. It can scarcely be denied, that on such difference mainly, if not entirely depends the difference in the prevalence of many febrile endemics; in one instance causing many, in another few attacks; now leading to a sweeping epidemic, and then giving rise to a few cases, or to one case. It would, in short, be necessary to show that while we are trying to trace the disease from one person to another, its cause is not springing from under our feet, and mingling with the air we breathe; which in the cases in question would not be an easy task, seeing that the disease had much endemic extension both before and after their occurrence, and that for years sporadic cases have been reported in the same or neighbouring localities. Nor will the doubts left in the minds of some enquirers, after full consideration of those cases, and allowing them all the weight they deserve, be lessened by reflecting on those which happened in the Minden and Rattlesnake respectively. But the case of the nurse in the “Dreadnought,” suggests questions respecting the fate of nurses attending choleral patients in other places. If it be true, as it is believed to be, that they are affected by cholera in a degree scarcely, if at all, exceeding that of persons in the same social condition otherwise employed, the fact would appear to furnish a strong general argument against the contagious nature of the disease. How does it happen that persons living in the same room with, and constantly handling and helping patients in all stages of the disease, so constantly escape its power, if it be not only readily communicable by the person to healthy persons, who are in juxtaposition with its subjects for a short time, but capable of being propagated by their clothes, in distant places, after undefined periods?