SLUMBER OF OLD EPIDEMICS. 115 



thousands are attacked. A careful examination of the 

 meteorological conditions affords no shadow of explana- 

 tion. At all temperatures, in every variety of humidity, 

 beneath every kind of skyey influence, these diseases be- 

 come epidemic. Time seems to have for them some kind 

 of bonds, for they seldom continue epidemic long, and do 

 not usually return as such, for a lapse of years. Ac- 

 cording to Humboldt, small-pox becomes epidemic in South 

 America, about once in from fifteen to twenty years, and 

 that sometimes without a known re-introduction. These 

 outbreaks seem to depend rather on germinal power than 

 extrinsic enforcement, and remind one of the locusts, 

 w r hich, though every year present in small numbers, ap- 

 pear by myriads at periods of from seven to seventeen 

 years. As the larvae of these insects lie deeply buried in 

 the earth, beyond the reach of anything but the mean 

 annual moisture and temperature, which are but slightly 

 varied, we have yet to learn what spell it is, which calls 

 them in countless throngs, into active existence. 



The plague-spell has not darkened the portals of Chris- 

 tian Europe for more than one hundred years, and the 

 sudor anglicanus has not floated on its fetid mists, since 

 the House of Tudor resigned to the Stuarts the throne of 

 England,. But these genii of a former age are but asleep. 

 Their time is not yet. When they shall again recover 

 their germinal vigor, and pass beyond their wonted limits, 

 or awake from their long repose, they will retain probably, 

 as before, their new activity or more extended dominion, 

 for a series of years. It is true that a happier age, in 

 comfort and cleanliness, and medical knowledge, has 

 arrived to check their progress, and to limit their deadli- 

 ness ; but it is vain to hope that any disease has been en- 

 tirely eradicated, or any germ totally lost. In a few 



