CHOLERA. 515 



may be safely reconimended. When an epidemic of cholera occurs in 

 winter, then a relatively low state of the ground-water is found to pre- 

 vail. In Munich three epidemics prevailed during the cold months : 

 the first occurred between October and March, 1836-37 ; the second 

 from July to November, 1853-'54 ; and the third from July till April, 

 1873-'74. All three epidemics were associated with a relatively dry 

 state of the earth, as was proved also by meteorological data concern- 

 ing the rainfall. No investigation has been made as to the state of 

 the ground-water during the period 1836 to 1854, but this investiga- 

 tion was first begun in 1856, so that for 1873 and 1874 the data were 

 available ; and it is only on the assumption that the condition of the 

 soil as regards moisture was abnormal for the time of year that the 

 long duration and strange division of the last epidemic could be ac- 

 counted for. The subsoil-water sank from the end of June, 1873, till 

 the beginning of August. On that occasion the germs of cholera prob- 

 ably came from Vienna, where the epidemic had prevailed since April. 

 Two cases coming from Vienna, one in June, the other in July, could 

 be vouched for. At the end of July the first illness from cholera oc- 

 curred in Munich, but in individuals who had never come in direct 

 contact with the infective cases. In every fresh outbreak, in 1836, in 

 1854, and in 1873, the same part (the northeast) of the town was the 

 first to suffer. As the epidemics of 1854 and of 1873 developed at the 

 same time of the year (the end of July), so by the middle of August 

 the height of the epidemic was reached ; it then fell off rapidly during 

 September ; during the whole of October only isolated cases occurred ; 

 and by the middle of November the epidemic had ceased in the higher 

 lying parts of the town. It was thought that the disease had become 

 extinct, and notwithstanding that it was considered strange that the 

 summer epidemic had chiefly fallen upon the higher lying parts of the 

 town, while the lower lying districts on this occasion had been alto- 

 gether spared. In the middle of November, when the weather became 

 colder, the epidemic reappeared, and attacked chiefly those lower lying 

 districts which had escaped in the summer. It is impossible to trace 

 the progress of contagion in time and space from one individual to 

 another. The contagionists can not maintain that the unexpected 

 falling off of cholera was due to the protection afforded by the pre- 

 vious prevalence of the disease, seeing that the lower lying districts 

 had escaped the epidemic, and that the other inhabitants two months 

 later suddenly lost their protection. Any one who studies the move- 

 ments of the ground-water in Munich for the year in question will find 

 that in the first half of August an event occurred which in suddenness 

 and unexpectedness rivaled the retrogression of the epidemic in the 

 second half of August. In the first half of this month there fell an 

 abnormally large quantity of rain (one hundred and seventy-one milli- 

 metres), which excessive rainfall was the largest amount ever regis- 

 tered since the observations had been begun. The consequent wetness 



