QUARANTINES. 113 



Nor should we be astonished at finding a surprising fe- 

 cundity at certain times in certain classes of plants, by 

 means of which they not only multiply prodigiously on 

 their customary soil, but readily advance beyond their 

 wonted boundaries. In this way I may explain the ra- 

 vages of the plague in Europe, and of the yellow fever in 

 North America and Spain; and account for the intrusion 

 of cholera upon European ground, and its failure to main- 

 tain its conquests for any prolonged period of time. The 

 plague retreats back to the Nile, Euphrates,* and Dan- 

 ube, its native home, the cholera withdraws to Hindostan, 

 and the yellow fever to the southern coast of America and 

 to the West Indies. It is twenty-six years since yellow 

 fever visited Philadelphia. During that time, there have 

 been many seasons of as great heat and drought as in 

 1793 and 1798, and, every year, arrive at our wharves, 

 vessels from infected ports; but the germs of disease do 

 not bear transportation always, and our fungiferous tend- 

 encies at home have not invited a visit. Long may it so 

 be in both respects! 



To speak of quarantine regulations, does not come pro- 

 perly within the scope of my subject, but the importance 

 of the question may perhaps excuse me for the suggestion 

 that, on the principles here "laid down, the detention at 

 quarantine even of the sick, is, for yellow fever and 

 cholera, unnecessary; while the importance of detaining 



* At Erzcroum, the capital of Armenia, the winters are cold, the ther- 

 mometer rarely rising above 32 F. and descending often as low as 25 or 

 even 20. In summer the heat has a range of from 66 to 81 5 ; yet 

 this place and its adjacent villages, seem to generate the plague. It ap- 

 peared there in 1840, about the middle of August, and in 1841, in the be- 

 ginning of July. 



10* 



