395 



the elevation of which a little exceeds that of 

 the Eneero, but of which the mean temperature 

 is above that of Xalapa. 



I have published in another work* the phy- 

 sical observations made by Mr. Bonpland and 

 myself on the locality of towns, that are period- 

 ically subject to the scourge of the yellow fe- 

 ver ; and I shall not hazard here any new con- 

 jectures on the changes observed in the patho- 

 genic constitution of particular cities. The 

 more I reflect on this subject, the more myste- 

 rious appears to me all that relates to those 

 gaseous emanations, which we call so vaguely 

 the seeds of contagion, and which are supposed 

 to be developed by a corrupted air, destroyed 

 by cold, conveyed from place to place in gar- 

 ments, and attached to the walls of houses. 

 How can we explain why, during the eighteen 

 years which preceded the year 1794, there was 

 not one single instance of the vomito at Vera 

 Cruz, though the concourse of unseasoned Eu- 

 ropeans and of Mexicans from the interior, was 

 very considerable ; though the sailors indulged 

 in the same excesses, with which they are still 

 reproached ; and though the town was not so 

 clean as it has been since the year 1800 ? 



The following is the series of pathological 

 facts, considered in their greatest simplicity. 



* Nouv. Esp t Tom. ii, p. 752—788. 



