No. of Places. Duration in Days. Average Population. 52 0 to 50 6,624 43 50 to 100000 12,624 33} 100 and upwards { 38,123 34} „ { 78,823 There was a similar relation in 1849 between the duration of the cholera and the population of the places which it visited; a relation which points clearly to the propagation of the disease from patient to patient; for if each case were not connected with a previous one, but depended on some unknown atmospheric or telluric condition, there is no reason why the twenty cases which occur in a village should not be distributed over as long a period as the twenty hundred cases which occur in a large town. Even the duration of the cholera in a street, when compared to its duration in the individual houses, points to the same conclusion. A table has been published[31] in the report of the late discussion on cholera at Munich, which shows that whilst the epidemic remained three or four weeks in a street, it only remained six or seven days in houses where several people were attacked. Dr. Pettenkofer remarks, that “if the proximate cause of the disease had been generally diffused over a certain number of streets or a certain district, and its invasion had been opposed by individual disposition alone, one might have expected that both the cases of disease and the instances of death would have occurred in single houses, where many such appeared together, at similar periods of time throughout the whole street; but, supposing that the proximate cause of the disease was not general, but local, then it would act in such a manner that the period of time within which the disease would show itself in single houses would be very different from that which was applicable to the entire street.” The local cause in a house we know to be the illness of some individual, who, in many cases, has newly arrived from some place where the disease was prevailing. [Sidenote: EFFECT OF SEASON ON THE PREVALENCE OF CHOLERA.]