5o6 TEE POPULAR SCIENCE MONTHLY. 



Lyons, the second largest town of France. Or, watching the passage 

 over smaller distances, in 1854 it went from Munich to Augsburg by 

 railway, leaving intact the ten intermediate stations, although several 

 patients alighted and some even died; and, notwithstanding that chol- 

 era raged at Augsburg and Lech, it never once sprang over the valley 

 of Lech to the town of Friedberg, which is but a league distant. Or, 

 to take a still narrower circle, cholera thrice (1836, 1854, and 1873) 

 invaded Munich, and every time halted in those houses situated on the 

 clay soil in the suburbs. 



The capriciousness of cholera may be observed in its relations not 

 only to space but also to time ; at one time it infected Prussia and 

 shunned Saxony, while at another it did exactly the reverse. In the 

 year 1849 Berlin experienced its worst epidemic, an epidemic in which 

 Saxony was but slightly affected (488 cases) and Bavaria not more so. 

 In the year 1850, when the cholera in Berlin and its environs had al- 

 most subsided, the epidemic raged in Saxony until 1,551 deaths oc- 

 curred, though Bavaria was not involved. In 1854 the matter was 

 altogether different ; then Munich and Bavaria had its worst epidemic, 

 at which time the Industrial Exhibition was held at Munich, and the 

 intercourse between Munich and Saxony and the whole of Germany 

 was very active. The cholera did not, however, spread to Saxony. All 

 the fatal cases of cholera in Saxony had taken the disease from Munich. 

 The epidemic did not spread farther north ; yet the inhabitants of 

 Saxony and Prussia had sufficient susceptibility for the disease, as was 

 proved when they went to Munich. It was in the year 1855 that a 

 change occurred ; then Bavaria was exempt, and the epidemic dev- 

 astated Saxony and North Germany. What relation the extension 

 from India by the agency of man may have to conditions of time and 

 space, to local and periodical disposition, has yet to be worked out ; 

 but the fact of the existence of relations in time and space is as unde- 

 niable as that of cholera itself. The cholera-germ alone will not ex- 

 plain everything. We must now inquire into the differences between 

 places which are and those which are not susceptible, and endeavor also 

 to trace out the relations in time which obtain in susceptible places. 



No doubt can be entertained that the configuration of the earth has 

 a certain influence. Relatively low-lying sites are very favorable to 

 cholera. Where the surface of the earth has an undulating outline, it 

 will be found that districts and individual houses which are situated 

 on the summit of the undulation very frequently have no, or only a 

 very small, disposition to the development of an epidemic of cholera, 

 while in the hollow of the undulation under like conditions the oppo- 

 site holds good. The truth of this statement is seen in single districts 

 where parts or single houses exist on the summit and others lie low. 



Another feature which is found in every epidemic is the falling off 

 of the disease in the neighborhood of and on mountain-ranges. The 

 Himalayan Mountains, those of Lebanon and the Alps, have always 



