CHOLERA. 621 



CHOLEKA* 



Br De. max von PETTENKOFER. 

 II. MODES OF PROPAGATION. 



HAVING now discussed the relations in time and space wlaicli pre- 

 dispose to cholera, I shall pass on to consider those relations in 

 regard to the freedom from cholera which they may enjoin. Places 

 which enjoy an immunity from cholera are more numerous than was 

 formerly supposed, but have been less studied from a point of view of 

 epidemiology, just as relations in time have been but little investigated. 

 The eye of the investigator has only fixed itself on the places where, 

 and at the time when, cholera has reigned. We ought likewise to in- 

 vestigate the matter when and where cholera does not exist. Ordina- 

 rily a physician only bestirs himself when he is called to see a case. It 

 has, however, not been so with me. Impressed with these notions, I 

 went in 18G8 to the place in Southern France which had enjoyed the 

 greatest and most renowned immunity from cholera. Through the 

 kindness of M. Fauvel, I was introduced to M. Luuyt, of Lyons. Al- 

 though Lyons was in frequent communication with Marseilles and 

 Paris when epidemics of cholera raged, yet the disease never showed 

 itself in an epidemic form at Lyons. In 1849, for instance, Lyons was 

 besieged, conquered, and invested by troops suffering from cholera. 

 Then the town escaped, while the soldiers suffered severely. This im- 

 munity was certainly not due to greater cleanliness of that quarter of 

 the town known as Croix Rousse ; nor was it due to the social misery 

 or to the wants of the working-classes ; neither had the drainage or 

 water-supply, which prior to 1858 was as bad as it could be, anything 

 to do in the matter. So that the immunity was probably the result of 

 natural conditions. The Lyonese had often congratulated themselves 

 on this excellent gift of nature, but it is probable that the constant 

 movement of air which the combined flow of two great rivers (the 

 Rhone and the Saone) originate is the cause of the immunity, although 

 the mistral {3IistralstUrme) which scours Languedoc and Marseilles 

 had never been able to drive the cholera away. The situation of 

 Lyons is far different : the bed of the two rivers is composed of com- 

 pact granite, which on the right bank of the Rhone and on both banks 

 of the Saone rises high, being in places coated with lias, molasse, and 

 thick mud strata. On the heights lie the parts of the town called 

 Croix Rousse, Fourvi^re, and St. Juste ; other quarters lie low — Per- 

 roche on a tongue of land between the two rivers, Lyon Vaise on the 

 right bank of the Saone, and Brotteaux and Guilloti^re on the allu- 

 vial soil of the left bank of the Rhone. The lower parts of Lyons 



* Reprint of a special translation made for the London " Lancet." 



